What Is a Water Cistern System?
Those living in a municipality often take for granted utility services that many rural property dwellers are not privileged to enjoy. Many people living in rural regions are extremely fortunate if they are able to afford the huge expense of drilling a water well (and even more fortunate if the drill actually strikes good potable water). For those rural proprietors or tenants who are challenged by the absence of a drinkable water source on their property, a cistern system is a practical and economical alternative.
- A water cistern is simply a water holding storage tank. For potable water, the cistern should be sterile and completely enclosed to keep unwanted debris from entering and contaminating the system.
- Water cisterns are available in all shapes and sizes and manufactured from many different types of materials. The selection is vast.
- Cisterns are fillable through a water inlet near the top or can be filled directly through the top cleanout or entry hatch. In the side wall near the bottom of the cistern is a water outlet; this is where a pump and some pipe fittings will be assembled.
- A pump is necessary to suck the water out of the cistern and, through some supply lines, push the water to the required usage point. Once you have all the equipment installed, all you need is water.
Step-by-Step Process for Building Your System
In this how-to article, we'll go over the following:
- Buying the Right Water Cistern
- Choosing a Pump
- Connecting the Pump to the Cistern
- Adding Water to the Cistern
- Where to Get Your Water
Buying the Right Water Cistern
Try to purchase a water cistern that is large enough to supply your water usage for a convenient amount of time. The biggest expense in filling your cistern is not the water, it is the transportation of the water. The less you have to haul water to your holding tank, the lower your overall water costs will be.
Calculate Your Monthly Water Demand
If you are only supplying your household with the water, you can roughly calculate the usage by figuring out how many times you do laundry (roughly 20 gallons per load), how much water you'll need to bathe (about 20 gallons per baths), how many showers you'll take (about 10 gallons per shower), and how many toilet flushes (roughly 3 gallons per flush). Then add the gallons used by those services together per week and then multiply that sum by 4 to get a monthly demand amount.
Under vs. Above-Ground Units
After you have the size calculated, you need to decide on its ideal location in your yard. You can put it underground, but construction costs will be much higher compared to above-ground setups.
However, if your region is susceptible to frigid temperatures, you may want to forego the expense of sheltering and heating an above-ground cistern system, although a well-insulated building just large enough to house your system is not too costly to heat— the interior temperature need only be a few degrees above freezing and the warmth supplied by a 200 watt heat bulb could be sufficient. If you burn a 200 watt bulb 24 hours per day, you use 4800 watts [200 watts/hour X 24 hours] of electricity or 4.8 kilowatts. If the cost of electricity is 11 cents per kilowatt hour (1000 watts/hour), the daily electrical consumption cost for your heat source is 53 cents per day or $15.90 per month.
Choosing a Pump
For your aboveground water system, you will need a pump. I found a 3/4 horsepower jet pump complete with a small pressure tank to be an economical choice in this application. The further away the demand point is, the larger the pump will need to be.
Pump documentation will provide the information on how much water can be pushed through a certain diameter line for a certain distance. Mine specifies it has a maximum capable output of pushing water through a 1" diameter line to a maximum distance of 50 feet. My water line is 25 feet in length and 3/4 inch in diameter, so the jet pump works well for me.
Connecting the Pump to the Cistern
Once the pump is in place, its inlet or suction will have to be joined to the outlet on the bottom of the cistern. You can construct this connection easily with a few pipe fittings available in a threaded or glued PVC plastic and a Galvanized (Zinc) coated steel. Though the PVC fittings are less expensive, they are not the best choice for outdoor use in a low temperature climate. They are fragile, not easily heated to unthaw when frozen, and their threads are not durable enough to be disassembled and reassembled numerous times as might be required for necessary maintenance or repairs. The galvanized steel pipe fittings are an investment that will pay dividends in peace of mind over the long run. The steel fittings should be galvanized so that they do not rust and release toxins into the water system. I elected to use the galvanized steel in this connection from the cistern to the jet pump suction.
- Beginning at the bottom of the plastic cistern wall, with a hole saw, I cut a 3" diameter hole about 3" up from the cistern floor.
- In that hole I installed a 3" 2 part PVC threaded flange with rubber gaskets which provides a leak-proof seal.
- After installing the flange, I used a 3" to 1" threaded bushing to reduce the 3" threads on the PVC flange to 1" threads for my galvanized suction line.
- I then used a few 1" galvanized pipe fittings such as nipples, and a 90° (elbow), an isolating valve, and a union to reach the location of the pump's inlet. It is important to install a union in this section so that the jet pump can easily be removed for maintenance if it fails.
- Remember, the union must be placed after the isolation valve so the water in the cistern can be contained when it is necessary to disconnect the pump. Both the union and valve are optional on the outlet of the pump.
- When the suction isolation valve is closed and the jet pump is unplugged from its electrical source, or when its power switch is turned to the off position, no water will come out of the pump outlet, so I do not use isolating components.
- The outlet is plumbed simply with galvanized fittings: 4" X 1" pipe nipple, a 1" coupling, a 1" to 3/4" bushing, and a 2" X 3/4" nipple. Over the 3/4" nipple I slide a 1" hose with two good quality hose clamps.
- The hose then runs to the demand area where it is connected similarly to the existing plumbing. Remember the outlet of the pump has pressure when it is in operation, so two clamps add extra protection making a more secure and reliable connection.
- The pressure switch on the jet pump (the rectangle box that the power supply connects to) comes preset at the standard user requirements of 20/40. This means that the pump will only stop pumping water when 40 PSI (pounds per square inch) is reached in the outlet line. The hose clamps have to hold 40 PSI. When the jet pump stops pumping, it will remain stopped until the outlet line pressure drops to 20 PSI, and then the pump will begin pumping once again.
- The pressure switch setting can be adjusted if the standard 20/40 setting does not suit your needs. Because the water system in my RV is older and maybe prone to fatigued connections, I set my jet pump pressure to 20/30, lowering the maximum output pressure by 10 pounds. Check your pump's documentation to see how to adjust its pressure switch settings.
Adding Water to the Cistern
Now, with the inlet of the jet pump plumbed into the cistern and the outlet connected to a hose that runs to the demand point, it is time to put some water in the holding tank.
Water can easily be transferred via gravity if we can get the transport tank elevation above the top of the cistern. I cannot achieve that height very easily out here so I use an economical 3" gasoline-powered transfer pump.
The setup is fairly simple, consisting primarily of two 20-foot-lengths of hose and the pump. For hose connections to the pump and water transport tote, I use rubber adaptor sleeves which can be found in the plumbing section at any local hardware store. They are thin, stretchable rubber tubes about 6" long with ratchet clamps on each end for joining the dissimilar pieces. They are economical and convenient for the temporary joining of two dissimilar materials of the same shape and do not require any turning for threads.
Once the hoses are joined to the transfer pump and the transport tote, I remove the top lid from the cistern, putting the pump's discharge hose in the opening. Then I start the transfer pump and open the tote valve, and in less than two minutes, I have 150 gallons in my cistern. Now I am ready to go and get another load.
Where to Get Your Water
Many municipalities have a coin-operated water station service. This convenience is provided to the growing number of rural property dwellers who are without a potable water supply. Such stations are usually operational year round and open 24/7. They are capable of pumping large amounts of water very quickly: The fill-up time for a 250-gallon transport tote is only about a minute. The cost for the water in most stations is extremely economical—a few dollars will fill your transport tote to the brim.
Questions or Comments?
I welcome all your questions and comments below as well as any suggestions or ideas of your own. Please share any input that you desire to contribute. I enjoy hearing from everyone.
How To Pam
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
Questions & Answers
Question: I want to place a rainwater cistern in my cellar, with a storage cistern in the attic. I understand the need for a pump and a connection to the rain gutters, but I do not know how to deal with any overflow. Will I need a different pump to get rid of the overflow?
Answer: If you want to gather rainwater through the gutters into a cistern in the cellar and then pump the water up to the attic water cistern, you should install a float switch in the attic cistern to cause the pump to cycle and fill the attic cistern when the water level falls to a low limit. To manager the cellar water cistern overflow you should consider installing a float switch to the same pump to cycle excess water to an exterior water holding tank. This can be accomplished with an electric solenoid valve at a "TEE" in the attic water line. Through this method you can use one pump to serve both functions.
Question: How do I clean out an old unused cistern to begin using again?
Answer: If the cistern is a proper potable water cistern, it should have a built-in manway or hatchway that is large enough for an average sized person to enter. Therefore, a person can enter the cistern and scrub the ceiling, walls, and floor with warm water and dish soap solution. I have also used a small amount of liquid household bleach, following the instructions recommended for cleaning kitchen countertops and sinks, etc. If the cistern hatch is too small to allow a person to enter, clean of the cistern can be done through the hatch with aids such as telescopic poles for painting, etc. Perhaps even a power washer wand could be inserted through the hatch and utilized, offering the advantage of water pressure. In the past, I have cut an opening in the top of a water cistern large enough to allow easy cleaning. I then fabricated a cover for the opening out of plywood, rubber gasket material, and stainless steel bolts. The piece cut out of the cistern can be fastened to the plywood cover so to fit back into the opening where it was cut from. If a person is to enter the cistern through an appropriate hatch, it is very important to be certain the cistern is well ventilated before and during the cleaning process.
Robert Ashton on February 16, 2018:
Why don't you catch rain water?