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This article describes the use of cisterns as a drinking water supply source including rooftop cisterns, attic cisterns, ground-level and below-ground-level water storage cisterns. We also discuss the acceptability of cistern water supply for HUD financed properties.
Cisterns and How to use them for Drinking Water Storage
A cistern is basically a water reservoir of any kind which is used to accumulate and store water for future use. Cisterns are usually constructed close to the
building which will use their water, sometimes even inside it.
Water from a cistern is typically pumped out by hand, drained by gravity, or
it may be pumped by an electric pump such as a one line jet pump.
Interestingly the owner broke through into the cistern
from the basement and drilled a modern steel casing well right in the bottom of the cistern - some of the new equipment is also visible.
Cisterns to store water for drinking or agricultural purposes are widely used in dry areas where rainwater runoff may be stored for future use.
However all water storage cisterns that are to be used for drinking or potable water supplies are at risk of contamination either from external sources or from bacterial growth during the water storage interval.
Cisterns may be located inside or outside of a building, and may be above ground or below ground level. Our photograph of a concrete cistern (above left) was taken in the basement of a 1920's home in New York state.
Also see Water Tank Types and before assuming that a water problem is due to the
well itself, see Water pump and pressure tank repair diagnosis & cost an specific case which offers an example of diagnosis of loss of water pressure, loss of water, and analyzes the actual repair cost.
Also see PLASTIC CONTAINERS, TANKS, TYPES and see WATER TANK SAFETY. Our page to photo shows an agricultural cistern located in central Mexico. This cistern was fed by a pump delivering water from a nearby drilled well that in turn had been sunk in the bottom of an older hand-dug well. Traditionally and still in some parts of the world people direct roof runoff from the
rainy season into a cistern where it is stored for use during dry periods.
Cisterns in attics are an open-type water storage reservoir or a water pressure boosting system similar in function to rooftop cisterns and water storage tanks.
A cistern was generally placed where it could be fed by gravity from roof or surface runoff, but any indoor open
topped reservoir of water could be called a cistern.
Attic Cisterns or water tanks are installed in some buildings
to perform the same function as rooftop-mounted water tanks. Other smaller
attic containers that look like a water reservoir may have been just an
expansion tank for the heating boiler system.
Basement & Indoor Cisterns in Older Homes
The basement cistern shown below is located below a pre-1900 home in New York. Later owners broke open
a passage into the basement cistern and now use it for storage. This cistern
was originally filled by downspouts directing roof runoff into the basement.
In the U.S. cisterns were often located in
the basement of a (pre-1900) home.
The cistern at left was built abutting the home foundation wall, probably filled by roof drainage and downspouts, and was later abandoned. The building owners later drilled a well in the floor of what had been a cistern and broke through the foundation wall to give ready access to the rest of the home's basement.
Finding Abandoned Cisterns
Cisterns inside older buildings can be tricky to spot - the cistern may have been partly demolished, such as in photos shown above, or the cistern may be a walled structure whose top is just below the joists of the building's first floor, as we see in the photos just below.
A tip that led to our discovery of this cistern was an unexplained drainpipe protruding to outside through a building wall. We traced the drain to a nearly-hidden basement cistern where it handled cistern overflow.
Watch out: an abandoned cistern, like any abandoned tank or excavation at a property, may be unsafe or a child hazard.
In a seasonally damp climate such as New York, an in-use basement
cistern would certainly be a likely source of unwanted building moisture
Open Water Tanks Indoors Form Mini-Cisterns for Spring-Fed Water Supplies
An open indoor water tank (photos below) can also function as an intermediate limited-quantity water storage tank or in effect a "mini cistern" that stores local water for a building fed by gravity from an up-hill spring or artesian well.
At some locations there is an up-hill or rooftop water source which is fed into the building entirely by gravity.
The open top water tank in these photos used a simple float valve to let water into this storage tank.
Where such intermediate storage tanks, perhaps fed by an uphill spring, were located in the upper floors of a building
they fed water to building piping where it could flow by gravity when a water tap was opened.
Our photographs show that this indoor water tank has rusted-through and is no longer functional, but the float assembly (photo above-right) makes clear how the tank worked.
Free-standing Water Tanks Function as Large Cisterns at or Close to Ground Level
Here we show two types of freestanding above-ground water storage tanks, at the Taboada Hot Springs (Guanajuato, Mexico, photo at left), and in Dutchess County, NY (photo below right).
Rainwater Storage Tanks & Cisterns
Outdoor Cisterns, are often located in the basement or courtyard of buildings where they
collect rainwater for future use. In arid areas such as the U.S. Southwest
and parts of Mexico, very large cisterns are often placed in a courtyard where
they collect rainwater for use during the dry season.
We prefer the ground-level water storage cistern shown below to the more traditional below-ground cisterns because the above-ground or on-ground rainwater tank can at least avoid contamination from surface water runoff that otherwise can enter a below-ground cistern.
In a seasonally damp climate such as New York, an in-use basement
cistern would certainly be a likely source of unwanted building moisture
and would thus be a risk for problematic mold growth.
In arid areas such as the U.S. Southwest
and parts of Mexico, very large cisterns are often placed in a courtyard where
they collect rainwater for use during the dry season.
The above-ground water cistern storage tank shown in our photo (left) is located in Mexico and is discussed at PASSIVE SOLAR HOME, LOW COST.
The tower's height provides water pressure to the building. Currently water is taken out of the bottom of this tank by a simple tank drain valve and hose attachment; to supply this water upwards to the building plumbing fixtures or perhaps to the cistern, a small electric pump will be installed.
Safety: be sure the cistern is of sound construction and that it is safely covered or protected from someone falling into the cistern or from a child climbing into it. Also see details at WATER TANK SAFETY.
Direct roof runoff, not surface runoff, into the cistern. Some clever roof runoff management systems direct the first roof runoff onto the ground, permitting dust and debris from the roof surface to be disposed-of before the remaining roof runoff is directed into the cistern for water storage. Other water sources may be used to supply cisterns, including even local or municipal water supplies. In this case the cistern is being used as a backup or off-peak water supply source.
Do not assume that water stored in a cistern is potable prior to filtering and treatment. The water should be tested for contaminants before used for drinking; it's fine to use cistern water for watering plants or lawns if that water usage is suitable and permitted by other conditions.
Do not install an open, un-covered cistern in a building where moisture from the cistern could cause a mold or rot problem.
Plastic Water Storage Tank Health & Safety: some water storage tanks are made of plastic polyethylene terephthalate aka PET. PET plastic water tanks may be a health risk to consumers: Commentary published in Environmental Health Perspectives in April 2010 suggested that PET might yield endocrine disruptors under conditions of common use and recommended research on this topic.
Proposed mechanisms include leaching of phthalates as well as leaching of antimony.[14] Other authors have published evidence indicating that it is quite unlikely that PET yields endocrine disruptors.[15] - Web search 6/27/2010 Wikipedia.
We discuss how to identify the type of plastic used in a water tank and the health and safety of different types of plastic tanks in detail at
Provide access to the cistern for inspection and cleaning
Pumps for cisterns: if you intend to rely on an electrical pump to move water from the cistern to its point of use during bad weather and possible power outage your pump will need a backup source of electricity. See PUMP, WATER PRESSURE BOOSTING
Attic Cisterns or water tanks are installed in some buildings to perform the same function as rooftop-mounted water tanks. This little attic reservoir found in the Justin Morrill historic home.
Attic expansion tanks and pressure relief systems Don't confuse
an old heating system attic-mounted expansion tank for a water tank however. These are not potable water storage systems.
The heating system expansion tank will be connected to the heating system
radiators or basement boiler and may have a simple overflow pipe
to permit excessive water (or system pressure) to spill outside.
Heating
systems with this equipment installed may not have a modern pressure and
temperature relief valve.
Attic expansion tank systems used on heating boilers are potentially less safe than installing a relief valve right on the boiler, since the
attic-located pressure relief system is located so remote from the heating boiler.
Is a Cistern an Acceptable Water Supply for HUD Financing?
Cisterns and HUD financing: HUD Handbook 4150.2 Section 3-6 indicates that properties served by cisterns are not acceptable for mortgage insurance. However, the HOCs have the authority to consider waivers in areas where cisterns are typical.
Our photo (above left) shows a hybrid system: this outdoor cistern is filled by pumping from an open casing in a drilled well that was inserted in the bottom of a dug well that went "dry" (photo, above right).
As will be apparent to readers, both the open top of this cistern and the open casing in the bottom of the dug well are sources of water contamination.
See WELL CLEARANCE DISTANCES for more information about cisterns, well and water source clearances from potential pollutant sources, and possible exceptions that can permit use of cisterns for drinking water supply.
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