ISSUED: 9-90
J.L. Taraba & E. Holmes, Agricultural Engineering Department
T.W. Ilvento, Dept. of Rural Sociology
L.M. Heaton, Dept. of Human Environment: Design & Textiles

When an adequate supply of high-quality well or spring water can be found near one's home, this is the best system to develop for the family's primary water supply. However, this solution is not always feasible. In many parts of the state, groundwater may be inadequate or hard to find. Sometimes the volume of water may be adequate, but excess impurities make treatment impractical.
Although a number of rural water districts have been formed to bring community water into areas with inadequate or undesirable supplies, high connection costs have limited their use. A few families have developed ponds as a water source, but they also have a high initial expense and are costly to maintain and protect from contamination.
Many families throughout the state must get their water from cisterns. When properly designed and maintained, cisterns can be a reliable water source. This publication deals with solving some of the problems associated with using a cistern:
designing the cistern system
avoiding water pollution
purifying the water
removing undesirable taste and odor from the water and
keeping the cistern clean.

Planning for a Cistern
When the home water system is supplied by a cistern, it includes a roof or catchment area, roof gutters, downspouts, downspout diverter, roof washer and a holding basin or cistern (Figure 1). A sand filter and a chlorine treatment system are very important components in assuring better quality water.
Major factors in planning a cistern are the frequency and amount of rain, size of the roof or catchment area (the flat length times width at the eave), construction materials and the family's daily water needs. In Kentucky, the average annual rainfall varies from 40 inches along the northern border to 50 inches along the southern border (30-year average) (see Figure 2). The longest average period without at least 0.1 inch of rain is 11 days. Although October is normally the month of least rainfall, droughts can occur anytime during the year.
Assuming that a family of four uses water conservatively, the 12' wide x 12' long x 9' deep cistern (plan KY 11.855316) would hold a 48-day supply (assuming 50 gal. per person per day). Longtime rainfall averages show that a 3,000 sq. ft. roof will supply this family's need except during very rare long droughts. Few homes are this large, so many families may have to use a barn roof or a combination house and barn for sufficient catchment area. With a 50-inch annual rainfall (southern edge of state), 2,600 sq. ft. of roof will supply the same needs.

Figure 3 will help one to select a cistern size to best fit the catchment area available. If the catchment area is only 1,800 sq. ft., the annual water supplied with 40 inches of rainfall would be approximately 26,000 gallons. This figure takes into account that one-third of the rainfall is lost in roof washing, evaporation and system leaks. With a limited roof or catchment area, families must depend on hauled water during dry periods. Within reason, an oversized cistern is a good investment to take advantage of periods of heavy rainfall.

Roof Washers
Since roof contamination accumulates between rains, a roof washer is a wise investment (Figure 4). The roof washer allows the first gallons of rainwater from the roof to be diverted from the cistern. The amount of roof contamination depends on the length of time since the last rainfall and the proximity of the roof to dusty' roads or any other source of airborne deposition, such as the local bird population and wood or coal stove chimneys.
A Pennsylvania study estimated the first O. 1 inch of rain as adequate to clean the roof. On a 2,000 sq. ft. roof this would amount to 12.5 gallons. This prewash could be done with a manually operated bypass valve, but there are problems such as forgetting to flip the valve to the cistern or being away from home when rain fell.
A roof prewash can be ineffective if the precipitation fails through trees overhanging a catchment area. Trees also collect atmospheric dry precipitation. Rainwater passing through foliated trees accumulates organic compounds exuded from leaf surfaces which affect the taste of cistern water. These organics also contribute to bacterial growth in the collected cistern water.

Well-designed gutters are a very important part of the cistern system because they can prevent wasting water. A 5" o.g. gutter and a 3" downspout can handle 700 sq. ft. of roof catchment. For 1,100 sq. ft. of roof catchment a 6" o.g. gutter and a 4" downspout are needed.
The gutter needs to have a slight but not excessive fail toward the downspout. For example, a 3-inch drop along a level cave will waste much water at the lower end during a heavy rainfall.
Gutter guards consisting of 1/4" hardware cloth (Figure 5) will help to keep the gutter and cistern clean of leaves and other debris. However, gutters need a periodic cleaning because of materials that clog the guard and settle in the gutter.
Gutters must be securely anchored to the roof because heavy snow and ice can tear them loose. Gutters on eaves away from the cistern are connected with crossover downspouts (Figure 1).

Sand Filter
An optional sand filter made up of sand and gravel (Figure 6) will remove some contaminants and, if the gravel is limestone, will partially neutralize acidic rainwater. A filter must be backwashed regularly, or it will encourage bacterial growth and leaching of chemicals from trapped particles.
The top two inches of a sand filter can become clogged with sediment. A mat can also form from bacterial activity that will eventually plug the sand and make it ineffective. It should be periodically removed and replaced with new sand. CAUTION: It is important to use washed, screened beach or quarried sand in this filter.
A sand filter must also have a very large surface area to filter heavy rainfall. For example, a 4' x 4' filter will be adequate for a 1,500 sq. ft. roof. Even then a very heavy rainfall will overflow.
The filter outlet from the bottom layer of gravel must be as large as the downspout inlet. The cistern top should not be used to support a filter unless it has been constructed to bear such a heavy load. Each cubic foot of rock and sand can weigh up to 150 pounds.

Cistern Materials
Cisterns can be made of reinforced concrete, reinforced concrete block, fiberglass and plastic-lined or metal tanks. Because of problems with rust, very few metal cisterns are found, although their initial costs are the lowest.
Masonry-walled cisterns help neutralize water to reduce corrosiveness and precipitate out any heavy metals dissolved in the rainwater. These heavy metals then accumulate in the sludge at the cistern bottom. Metal or plastic-lined cisterns or non-masonry sealed inside walls do not allow this process to occur.
There are many concrete block cisterns throughout the state as they normally cost less to build than poured concrete. Block cisterns are hard to adequately reinforce and consequently crack more, allowing water to leave or outside water to enter the cistern. Their many joints compound the problem by providing more chances to leak.
The poured reinforced concrete cistern (Plan Ky 11.8553-16), when properly built, makes the best cistern. However, this is true only if quality materials and standards are used in construction. This starts with a good set of forms properly set after the foundation is poured. The foundation and floor must be placed on firm soil. It is important to place the reinforcing rods so that they will not shift while the concrete is being poured. The concrete must be a stiff mix of one part cement, two parts clean sand and three parts gravel (max. 3/4").
Rounded shingle gravel is better than crushed stone for making a water-tight concrete. Any sand or gravel should be thoroughly washed before using because the cement paste will adhere better to a clean surface. The concrete should be poured continuously to prevent seams and should be air entrained for better curing and water-tightness in adverse weather. Tamping or vibrating the concrete in place will prevent honeycomb walls. Excess water should not be used because its evaporation will leave the concrete porous.
Since an overflow pipe for the cistern is recommended one foot below the top, the top can be poured separately after the sidewall forms are removed, making the roof forms easier to place. The overflow pipe must be screened with 1/4" hardware cloth on the outside to keep out rodents, snakes, etc. A water inlet located convenient to the roof downspout must be placed in the top of the cistern. This inlet must be sealed to prevent any contamination by surface water.
A 24-inch manhole with raised edges to form a curb (to prevent water entry) must be located near an outside edge of the cistern for access when cleaning or repairing. The manhole cover must be heavy or have a lockable cap to prevent small children from falling into the cistern.
The cistern floor should slope slightly (a minimum of 1" per 12') toward a small sump area under the manhole. The sump area makes it easy to use a sump pump for cleaning if the ground slope of the cistern site does not allow for a natural drain. A drainage tile around the outside of the cistern at floor level is advisable if the land slope drops enough to accommodate a gravity drain or if the tile can be drained to the home's drainage sump. This will relieve groundwater pressure on the wall when the cistern is empty.
To assure water tightness, the cistern wall should be plastered inside and out. The outside should then be treated below grade with a waterproof sealant. The inside plaster should be coated with a high-quality masonry sealant.
The cistern should be buried to the level of the overflow pipe for the following reasons: (1) to give ample room for the roof washer on top of the cistern, (2) to make yard landscaping easier and (3) to help keep cistern water from freezing.

Sources of Cistern Contamination
Many people think of cistern water as being pure, but this may not be true. Matter that settles on the roof supplying the cistern, such as organic matter from trees, airborne contaminants from burning wood or coal or droppings from birds in addition to bacteria buildup in sand filters, sediments in the cistern and an unclean cistern itself, can contaminate the water. Water that is hauled can also be contaminated.

Bacterial Pollution
Bacterial contamination may be found in any cistern water, suggesting the need for periodic testing for coliform bacteria, which can indicate the presence of pathogenic bacteria. Maintenance should include a regular cleaning and disinfection of the system.
A Morehead State University study found bacterial contamination by coliform bacteria in 27% of the cisterns tested. A study conducted by Northern Kentucky University indicated that 68% of the cisterns tested were contaminated with coliform bacteria. The Northern Kentucky study also identified the presence of heterotrophic bacteria in significant numbers. Some of these bacteria are not pathogenic but opportunistic. They can affect individuals with compromised or weakened immune systems or those who take heavy antibiotic medications and anticancer drugs.
The heterotrophic bacterium Pseudomonas aeruginosa has been associated with ear infections and some intestinal upsets. Heterotrophic bacteria cannot be completely eliminated through chlorination, as can coliform bacteria, but their numbers can be greatly reduced. P. aeruginosa bacteria are eliminated.
In instances where the water may be contaminated with bacteria, a chlorination treatment unit may be installed. This can be a chlorine pump or a batch treatment process.

Chlorine Pump System
A chlorine pump injects chlorine into the water as it enters the house. In this system, contact time with the chlorine is very important to kill bacteria. A practical chlorine contact time is usually from two to five minutes for a free chlorine concentration of 2 mg./liter, with five minutes recommended for a margin of safety. This requires quite a length of pipe or a large storage tank between the point of injection and end use. This time is affected by the water pH, temperature and amount of bacteria. As an example, water with a pH of 6.5 and 50 degrees F or higher will have a "K" value of 4 (for additional specific "K" values, see Table 1).
For a pH of 7.5 and 50°F or higher, the contact time would be six minutes. The value of K for other combinations of water temperature and pH is found at Table 1. The design must be based on the coldest expected water temperature.
If the pump capacity is five gallons per minute, 375 feet of 1 1/2" pipe or a 25-gallon storage tank is needed between the point of chlorine injection to the end use point to provide the five-minute contact time. For longer contact times, a storage tank is preferable to pipe because of excess pressure drop for the required length of pipe to obtain the proper contact time.

Water pH
Expected water temperature
50oF or 
45 40oF or 
6.5 4 5 6
7.0 8 10 12
7.5 12 15 18
8.0 16 20 24
8.5 20 25 30
9.0 24 30 36

4 5 6 7 8 9 10 11 12 13 14 15
16 480 600 720 840 960 1080 1200 1320 1440 1560 1680 1800 4
25 750 937 1125 1312 1500 1687 1875 2062 2250 2437 2625 2812 5
36 1080 1350 1620 1890 2160 2430 2700 2970 3240 3510 3780 4050 6
49 1470 1837 2205 2572 2940 3307 3675 4042 4410 4777 5145 5512 7
64 1920 2400 2880 3360 3840 4320 4800 5280 5760 6240 6720 7200 8
81 2430 3037 3645 4252 4860 5467 6075 6682 7290 7897 8505 9112 9
100 3000 3750 4500 5250 6000 6750 7500 8250 9000 9750 10500 11250 10
121 3630 4537 5445 6352 7260 8167 9075 9982 10890 11797 12705 13612 11
144 4320 5400 6480 7560 8640 9720 10800 11800 12960 14040 15120 16200 12
169 5070 6337 7605 8872 10140 11407 12675 13942 15210 16477 17745 19012 13
196 5880 7350 8820 10290 11760 13230 14700 16170 17640 19110 20580 22050 14
225 6750 8437 10125 11812 13500 15187 16875 18562 20250 21937 23625 25312 15
256 7680 9600 11520 13440 15360 17280 19200 21120 23040 24960 26880 28800 16
289 8670 10837 13005 15172 17340 19507 21675 23842 26010 28177 30345 35512 17
324 9720 12150 14580 17010 19440 21870 24300 26730 29160 31590 34020 36450 18
361 10830 13537 16245 18952 21660 24367 27075 29782 32490 35197 37905 40612 19
400 12000 15000 18000 21000 24000 27000 30000 33000 36000 39000 42000 45000 20

4 5 6 7 8 9 10 11 12 13 14 15
4 378 472 566 661 755 850 944 1038 1133 1227 1322 1416
5 590 737 885 1032 1180 1327 1475 1622 1770 1917 2065 2212
6 850 1062 1274 1487 1699 1912 2124 2336 2549 2761 2974 3186
7 1156 1445 1735 2024 2313 2602 2891 3180 3469 3768 4047 4336
8 1510 1888 2266 2643 3021 3398 3776 4154 4531 4909 5286 5664
9 1908 2385 2863 3340 3817 4294 4771 5248 5725 6202 6679 7156
10 2360 2950 3540 4130 4720 5310 5900 5490 7080 7670 8250 8850
11 2856 3569 4283 4997 5711 6425 7139 7853 8567 9281 9995 10708
12 3398 4248 5098 5947 6797 7646 8496 9346 10195 11045 11894 12744
13 3988 4985 5983 6980 7977 8974 9971 10968 11965 12962 13959 14956
14 4626 5782 6938 8095 9251 10408 11564 12720 13877 13033 16190 17346
15 5310 6637 7965 9292 10620 11947 13275 14602 15930 17258 18585 19913
16 6006 7516 9026 10537 12047 13558 15068 16578 18089 19599 21110 22620
17 6820 8526 10230 11938 13641 15346 17051 18756 20461 22166 23871 25577
18 7646 9558 11470 13381 15293 17204 19116 21028 22939 24851 26762 28674
19 8520 10650 12779 14909 17039 19169 21299 23429 25559 27689 29819 31949
20 9440 11800 14160 16520 18880 21240 23600 25960 28320 30680 33040 35400

In the above examples, a free chlorine disinfectant concentration of 2 mg./liter has been used. This level of free chlorine will leave a taste that may be unacceptable. Public water supply systems use a concentration of 0.2 to 0.5 mg./liter, but the continual monitoring of the water by trained personnel allows them to use this low concentration. In this case, the contact time will be at least 20 minutes. The cistern owner can use activated carbon to remove the excess chlorine before the water is used for drinking or cooking.
If an automatic chlorination system was available to treat rain water as it entered the cistern, contact time would not be a problem. However, the fluctuation of rainfall volume has so far prevented uniform automatic treatment.
The owner can test cistern water for the concentration of free chlorine and pH using a kit available where swimming pool supplies are sold. A kit that can perform between 50 to 100 tests costs in the range of $5-$10; replacement chemicals cost less than $2.

Batch Treatment Process
Batch treatment, an alternative to chlorine injection, is usually done manually as new water from precipitation or hauled water is added to the cistern. To use the batch chlorination system, first determine the cistern water volume by measuring depth, width and length (for a circular cistern, measure the depth and diameter). Then use Table 2 or 3 to determine gallons of water in the cistern. Since free chlorine dissipates with time, weekly treatment is necessary if new water is not added to prevent high bacterial population from returning.
After the water volume is determined, add 1 ounce (volume) of 5% chlorine bleach per 200 gallons of water to the cistern weekly. This gives a maximum disinfectant concentration of 2 mg. free chlorine/liter. This concentration leaves a chlorine taste to the water which dissipates with time.
Batch treatment requires agitation to thoroughly mix the water with the chlorine. Bacteria are eliminated from the water, but sediments in the cistern bottom still contain very high bacterial populations that can contaminate the water above when the free chlorine dissipates. Cistern water that was superchlorinated (3 to 5 mg. free chlorine/liter) did not eliminate the indicator bacteria (coliforms and P. aeruginosa) in the sediment. Since this sediment mixes with the fresh water each time hauled water is dumped into the cistern, contamination of this water is possible.
A baffle or splashplate will help but not completely eliminate this risk. A splashplate breaks the force of water entering the cistern through the inlet during a rainfall event or while filling the cistern with hauled water.

Other Sources of Contamination
Today we read much about water pollution from chemicals, industrial waste, acid rain, etc. It is possible for these to get into any water source, but with a well-designed cistern that prevents surface or groundwater from entering, chemical contamination can only come from air pollution through wet or dry deposition on the rainwater catchment area or from hauled water that was contaminated before reaching the cistern.
While there is no detailed study of the chemical composition of cistern water in Kentucky, a study under way for monitoring acid rain precipitation throughout the state should tell us something about the water going into our cisterns. Precipitation (rain or snow) is the prime source for cistern water. So far, precipitation has been found to have a highly acidic pH of about 4.3, primarily due to sulfates and nitrates. Trace amounts of heavy metals have also been identified. The higher concentrations are found around industrial areas.
Since cistern water comes from a roof, contamination could be greater than that found by measuring only precipitation composition. Between precipitation events, dry deposition (sometimes called dry fall) can settle on the roof and add to that caught by the wet deposition. This is a prime reason for a roof washing mechanism such as the one shown at Figure 4.
A study in the Virgin Islands (where families are heavily dependent on cisterns) found no significant contamination from roof paints or roof materials. Most of these roofs were galvanized metal. An Arizona study found no evidence that deterioration of such catchment material as common asphalt and fiberglass roofing contaminated runoff water. No information was found involving asbestos.
The National Sanitation Foundation is evaluating paints, coatings, sealants and synthetic liners for use in potable water systems for the EPA. An updated list of this evaluation is available from the local Cooperative Extension office or the University of Kentucky, Department of Agricultural Engineering.
One cistern water study designed to compare acidic deposition in Kentucky and Tennessee (an area known to receive acid rain) with that in St. Maarten, Netherlands Antilles (an area far removed from any industrial area), sampled 25 masonry cisterns at each location and found concentrations of metals in all the cisterns below the recommended safe level. However, water that remained in the home plumbing system overnight exceeded the proposed drinking water standards in 18 homes in Kentucky-Tennessee and 10 homes in the Antilles.
The study found no relation between roof materials, plumbing and metal concentrations. As would be expected, the mean pH was more acidic (7.00) in Kentucky-Tennessee than the Antilles (7.61). Sodium content of the cistern water was more than three times as high in the Antilles. This was explained as being caused by ocean spray.
The Kentucky acid rain study sampled 15 lakes and found a slight variation in pH but none too far from neutral pH 7. This was explained by the alkaline soil constituents. Another significant observation was that many of the emission sources deposited the contaminants within a 50-mile radius of the source. During precipitation (rain or snow), the air is stripped of much of the sulfates, nitrates and heavy metals. Particulates greater than one micron will deposit within 20 miles and become part of the dry deposition between precipitation events. One study stated that 40% of all settleable particulates from a point source deposited within 50 miles.
A Pennsylvania study analyzed cistern water in two rural areas thought to be receiving air pollutants from the industrialized Ohio River Valley. In some 12 of the 83 samples analyzed, the cistern sediment water contained lead and cadmium at levels exceeding mandatory drinking water limits established by the National Academy of Science. A few samples of tap water also exceeded the limits. In the bulk precipitation samples collected, all failed to meet EPA drinking water limits for pH and corrosivity. The seriousness of these findings merit such a study in Kentucky, especially near urban and industrial areas as well as near large point sources of air contaminants.
In a Texas study, acid rain sampling found sulfuric and nitric acids near lignite power plants. Sand, gravel and charcoal filters, as used in the past, were found to be ineffective in removing these contaminants because the acid water would still leach them into the cistern water from the particles previously trapped in the filter.
The National Acid Precipitation Assessment Program studied wet deposition of nitrates and sulfates in the eastern half of the U.S. A five-year average annual deposition of sulfate was 25 Kg. per hectare (22.3 pounds per acre) in the southwest tip of Kentucky. The highest annual deposition was in the Henderson-Owensboro area and the northeastern tip at 30 Kg. per hectare (26.8 pounds per acre). For nitrates the southwest tip was 12.5 Kg. per hectare (11.15 pounds per acre), and the high was 15 Kg. per hectare (13 pounds per acre) along the upper Ohio River area.
Within the 50-mile radius from a significant source of SO2 and NOx, the estimated percent increase with wet deposition over the above regional values would be in the range 5 to 25% and for significant point sources of SO2 the percent increase in sulfate wet deposition could be as high as 50%. The total deposition, including wet and dry deposition, is estimated to be twice the wet deposition. Based on these estimates, the NO3-N in cistern water would range from 0.5 to 0.8 ppm, well below the health standard of 10 ppm for NO3-N. The SO4 concentration is estimated to range from 4 to 9 ppm, also well below the 250 ppm recommended health standard. No maximum wet or dry deposition standards have been established at this time although atmospheric concentration standards have been set.
No detailed data relative to heavy metal deposition is available for Kentucky, but a study in New York does offer some insight. This study correlated elevated heavy metal deposition with elevated levels of regional sulfate deposition. The study reported the source of the heavy metal and sulfates to be from coal-burning activities.

Effects of Burning Wood and Coal in the Home
Acid precipitation may contribute only a small fraction of the contaminants deposited on a cistern catchment area if there are nearby contaminant sources from coal- or wood-burning fireplaces and stoves. No data has been found to identify the amounts of chemicals that can be deposited from these sources, but observations around the outside of houses burning coal or wood in a stove will show ash, soot or oily substances as a result. The chimney exhausts have ash particles which contain heavy metals, organic particles and condensables which contain polyaromatic hydrocarbons (PAHs).
Many of the PAHs will condense on the particulate matter. Many PAHs are carcinogenic and one in particular, benzo-a-pyrene (BaP), has been shown to be highly carcinogenic. These substances can deposit on a nearby cistern catchment area and wash into the cistern during the next precipitation. The BaP emissions from coal stoves have been measured as high as 2.5 gm/106 BTUs of heat produced. This is almost 20 times that of burning wood in a stove and almost 60 times that of burning wood in a fireplace.
The exhaust emissions from wood stoves vary with type of stove, wood seasoning and type of wood. One study compared these factors on the exhaust particulates, particulate organic matter and condensable organics. The highest particulate emissions (a weight equivalent to 0.5 to 0.6% of wood burned) were found with green pine in both an unbaffled and baffled stove. These values were about three to four times higher than seasoned oak in the same type stoves.
Green oak and seasoned pine had particulate emissions two to three times that of seasoned oak in a baffled stove, but in an unbaffled stove these woods had lower particulate emissions and were similar to particulate emissions of seasoned oak in both stoves.
About half the particulates in the exhaust had sizes greater than 10 m and approximately 33% of the particulates were less than 1m. The large particulates settle out quickly while the 1 m particulates stayed suspended in the air unless captured by precipitation.
The condensable organics in the stove exhaust were comparable in baffled and unbaffled stoves for seasoned oak and pine and green oak (a weight equivalent of 0.3 to 0.6% of the wood burned), but green pine had approximately twice the condensable organic material emissions in both stoves.
In general, hard woods and seasoned pine had the lowest emissions from stoves used for space heating, while a coal stove contributes the most emissions, by a large margin, that would potentially deposit on a cistern catchment area.

Removing Undesirable Taste, Odor and Color
Eliminating musty taste and odor as well as color and suspended matter from cistern water is a concern of cistern owners. These problems are particularly associated with organics and the byproducts of microorganisms growing in the cistern water. A roof washer does not eliminate 100% of the contaminants.
Automatic treatment of water as it is drawn from the cistern is recommended if odor and organic compounds become the concern. A recommendation in the past was to allow water entering a cistern to pass through activated carbon which has the ability to absorb organics. Further research has shown that when untreated water (water that is not decontaminated to eliminate pathogenic microorganisms and reduce total microorganism counts) passes through a carbon filter, microorganism and pathogenic organism counts increase. Furthermore, without regular replacement, activated carbon filters become saturated with organics and are no longer effective. Bacteria growing on carbon filters clog the microscopic pores of activated carbon and therefore reduce its effectiveness. At present, activated carbon is not recommended for use in treating water entering a cistern.
Activated carbon filters could be used if the water is decontaminated before reaching the activated carbon. Proper use and maintenance of activated carbon become important to obtain the maximum effect.
Treatment capacity cannot be assured in the same manner as when a carbon filter is used on regulated public water supplies. Changing filters at least every three months and/or when taste and odor are detected or increased would be basic maintenance guidelines. Further information concerning activated carbon filters can be obtained through your local Extension office (Carbon Filters, Cooperative Extension Publication #IP-6).
A batch treatment can be used for reducing taste and odor in cisterns. The following treatments are recommended:

Odors or Tastes:
1.The first step is purification by chlorination as previously described. The taste of chlorine should disappear in 24 to 36 hours after treatment.
2.If the taste of lime is not removed by cleaning the new cistern (see section on cleaning cisterns), use baking soda. Apply at the rate of 2 pounds of soda in 2 gallons of water for each 1,500 gallons of water in the cistern.
3.If water to the household is provided by a pressure pump, a commercial type filter using activated carbon or charcoal may be installed past the pressure pump. This filter will remove bad tastes and odors, but it will not purify the water. The water must be decontaminated before it passes through the filter.

Rainwater collected from sooty roofs and gutters or downspouts containing decayed leaves or twigs may have an undesirable dark color. Water from new roofs, especially those of wood shingles, may also have "off' colors. These colors can usually be removed by adding soda and alum to the water. These chemicals will form a sludge or sediment which will settle to the bottom in about 24 hours and carry the color with it. The solution should be prepared as follows:
Solution 1. Dissolve 3/4 pound of ordinary baking soda (sodium bicarbonate) in one gallon of water.
Solution 2. Dissolve 1 pound of alum (potassium aluminum sulfate crystals) in 1/2 gallon water. If available, 1/2 pound of "filter alum" (aluminum sulfate), which is cheaper than alum, may be used and added to 1/2 gallon of water. CAUTION: Do not use "Burnt Alum."
The number of gallons of water in a cistern may be found by using Table 2 or 3 as previously described. For each 30 gallons of water in the cistern, add 1/2 pint of solution No. 1 and stir, then add 1/4 pint of solution No. 2 and stir again. The amount of precipitate is relatively small and can be removed from the bottom of the cistern when it is emptied and cleaned.

Cleaning A Cistern
Before a cistern is used, it should be cleaned and disinfected by scrubbing the interior with a solution of 1/4 cup of 5% chlorine bleach mixed in 10 gallons of water. CAUTION: Be sure there is ample ventilation for the workers inside the cistern. Before the cistern is filled with drinking water, the interior should be hosed down until the chlorine odor disappears; then the cistern should be drained.
A cistern should be cleaned every five years or more often in areas with leaves or blowing dust or homes with coal or wood stoves. Follow the above cleaning practice each time the cistern is cleaned.
This material is based on work supported by the U.S. Department of Agriculture, Extension Service, under special project number 89-FWQI-I-9156.

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Sharpe, W.E. and E.S. Young. 1982. The effects of acid precipitation on water quality in roof catchment-cistern water supplies. Chp. 16. In: Acid precipitation: Effects on ecological systems. (ed.) FMD'Itri. Ann Arbor Sci. Publ., Ann Arbor, MI., pp 365-381.
Young, E.S. and W.E. Sharpe. 1981. Rainwater cisterns -- design, construction and water treatment. Pennsylvania State University, College of Agriculture, Special Circular #277.

Water Quality Terms
Acid rain -- Delivery of atmospheric acidic substances, primarily sulfur and nitrogen oxides, to the earth by rainfall.
Activated carbon -- Particles or granules of carbon produced by carbonization of cellulosic or other organic matter in limited or no air; possessing a very porous structure and highly adsorptive properties to remove some organic and inorganic contaminants and certain dissolved gases from water.
Benzo-a-pyrene (BaP) -- An aromatic polycyclic carcinogenic hydrocarbon (PAH) found in tars or smoke from incomplete burning of organics.
Carcinogen -- An agent that induces cancerous growth.
Catchment area -- A roof or receiving area from which water can be directed to a cistern.
Chlorination -- Use of chlorine gas or solution of liquid or solid chlorine compounds (hypochlorites) to disinfect water.
Chlorine bleach -- 5 1/4% solution of sodium hypochlorite (NaOCI) in water which has a 5% available chlorine content.
Chlorine demand -- The difference between the amount of chlorine added and the chlorine residual after a specific time. The amount of chlorine which is consumed by organic matter or oxidizable substances in water.
Chlorine residual -- Active chlorine in water that can react chemically (or free chlorine).
Cistern -- A water collection system where rainwater is captured (usually from a roof) and stored in a tank. Cisterns are often found in rural areas where public water or well water is not available.
Coliform bacteria -- A group of bacteria found predominantly in the intestines of humans or animals.
Condensable organic -- Organic compound that becomes a liquid at room temperature. Primarily refers to unburnt organic compounds found in smoke or exhaust from burning organics.
Contamination -- Any introduction into water of microorganisms or chemicals in a concentration that makes water unfit for its intended use.
Corrosiveness -- The tendency to wear away metal by chemical attack.
Disinfection -- The removal, inactivation or destruction of infectious or pathogenic microorganisms (bacteria, virus or protozoa).
Dry deposition -- Substances deposited on the ground or surfaces from the atmosphere between precipitation events.
E.coli (Escherichia coli) -- One species of coliform bacteria that indicates the presence of contamination by human or animal feces.
Fecal coliform -- Type of coliform bacteria found in human and animal feces.
Heavy metal(s) -- One or more of the following metals whose density is greater than 5 gm/cc: cadmium (Cd), lead (Pb), mercury (Hg), copper (Cu), silver (Ag), zinc (Zn), chromium (Cr), barium (Be), arsenic (As), selenium (Se).
Heterotrophic bacteria -- Bacteria that thrive only on organic matter for energy and growth.
Micron -- A unit of measure that equals 0.000039 inches (abbreviated as 1 m) is a micrometer (1 x 1011-6 meter).
Microorganism -- A microscopic organism, including bacteria, protozoa, yeasts, viruses and algae.
Neutralization -- The addition of either an acid to a base or a base to an acid to produce a neutral solution (usually considered to be a pH of 7).
Nitrate -- An inorganic anion NO3. Nitrates can be formed in the atmosphere when it contains NO3.
NO3-N -- Nitrogen in the nitrate form.
NOx -- Nitrous oxides NO2 and NO. They are formed primarily during high temperature combustion of fuels with air.
Pathogen -- Any microorganism that may cause a disease.
pH -- The strength of the acid or base present measured on a scale that runs 0 to 14 with a pH of 0 to 7 being an acid, a pH of 7 being neutral and a pH of 7 to 14 being a base.
Point source -- A discrete source of pollution, such as a readily definable pipe, stack or ditch.
Pollution -- A condition created by the presence of harmful or objectionable matter in water.
Polycyclic aromatic hydrocarbons -- Also known as polynuclear aromatic (PNA) hydrocarbons (PAHs) formed during incomplete combustion of fuels (coal and petroleum products) and cellulosic material (wood, paper, tobacco). They are multiringed hydrocarbon compounds (aromatics) that share two or more carbon atoms by two or more rings. Many compounds in this group are known carcinogens.
Potable water -- Water that does not contain objectional pollution, contamination, minerals or infective microorganisms and is considered satisfactory for domestic consumption.
ppb -- Parts per billion -- The number of weight or volume units of a minor constituent present with one billion units of the major constituent of a mixture.
ppm -- Parts per million -- The number of weight or volume units of a minor constituent present with one million units of the major constituent of a mixture.
Precipitation -- Condensation of water vapor in the atmosphere to form rain, snow, sleet or hail which falls onto the land and water surfaces.
Pseudomonas aeruginosa -- A gram-negative rod-shaped bacteria that is opportunistic to humans and can cause ear infections and intestinal diarrhea.
Purification -- The removal of objectionable matter from water by natural or artificial methods.
Reinforced concrete -- Concrete containing reinforcing steel rods or wire mesh.
Roof washer -- A device to divert away from the cistern the initial flush of water from the catchment area. This permits the catchment area to be washed of dust and debris.
Sand filter -- A device used to mechanically separate suspended particles from water, using fine sand as a filtering aid.
Sedimentation -- The process of settling the solid suspended particles out of water by gravity.
Settleable particulates -- Organic or inorganic particulates that settle or separate from the atmosphere or water by gravity in a given period of time.
Sulfate -- Inorganic anion SO4. Sulfates can be formed in the atmosphere when it contains SO2.
SO2 -- Sulfur dioxide. A gas that is formed by burning sulfur or sulfur-containing material in the air.
Wet deposition -- Also called acid rain.