Water Storage Tanks for a Low-Flow Well
When Pursuing Self-Sufficient Homesteading, Make Sure You Have Ample Water Supply
Reading Time: 6 minutes
By Gail Damerow — Water storage tanks can be a practical solution if your well doesn’t fill fast enough for normal household use. But how do you get a building permit if the flow is less than local code requires? A sizable water tank, or cistern, where the water will accumulate as it becomes available for use as it is needed. Our household water is furnished by a well that doesn’t draw enough water for a single start-to-finish load of laundry. The problem isn’t insufficient water. The well steadily produces approximately 720 gallons every 24 hours. That’s more than enough to satisfy our household daily average of 180 gallons.
By installing a 1,500-gallon storage tank, we are able to draw water from the well 24/7, using as much as we need during the day and making up the deficit at night while we sleep. We also have enough water to survive most any water emergency. Additional bonuses are having sufficient flow to satisfy the building inspector, plus qualifying for a reduced fire insurance rate.
While the 1,500 gallons would typically last our two-person household about a week, in a real tight pinch we’ve been able to stretch it to nearly a month. A larger household homesteading today would have more demanding water needs and would need to invest in some bigger water storage tanks. The accompanying “Estimating Water Use” table offers a start in figuring out how much water your households uses each day.
Having decided that we needed a cistern, the next decision was what type of water storage tanks to install. Our previous place came with an above-ground wooden cistern that forever needed clearing of frogs, insects, dead rodents, rotting leaves, and algae. Besides, it was highly visible from the front door, and took up surface space we could find better uses for.
This time we wanted a sealed underground tank. We looked for something economical, durable, and tight. Plastic is a potential health hazard. Steel and fiberglass tanks are durable and tight, but expensive. Wooden cisterns are cheap, but tend to leak and eventually rot. Concrete is durable, tight, not subject to rot or rust, and relatively inexpensive.
In some areas, you can buy a concrete cistern ready made. Another possibility is to construct your own. An online search for “how to build a concrete water holding tank” yields several sites offering step-by-step illustrated instructions. Wanting something that would go in fast, we opted for a single-chamber concrete septic tank, which required only minor modifications to turn it into a water storage tank.
We hired a backhoe to excavate a hole near our well, deep enough to put the tank under 18 inches of soil, which in our area is well below the frost line. At that depth, the water doesn’t freeze in winter, and remains cool and algae-free all summer. Farther north, the tank might need to be deeper to get below the frost line, and additional precautions would be necessary to protect pipes from freezing.
|Estimating Water Use|
|average per person||50-100/day|
|dish washing by hand||2-4/load|
|shower or bath||40/use|
|shower, low-flow showerhead||25/use|
|toilet flush, low-flow||1.5/use|
|laundry, top load||40/load|
|laundry, front load||20/load|
|laundry, hand tub||12-15/load|
|sow with litter||8/day|
|sheep or goat||2-3/day|
|laying hens, 1 dozen||1.5/day|
|turkeys, 1 dozen||2.5/day|
Making Modifications to Water Storage Tanks
We were lucky enough to accomplish all the necessary modifications and get the tank filled during dry weather. I say “lucky,” because subsequently we installed a second tank at our barn, and before it was filled with water and back filled with soil, heavy rainfall floated the tank out of the ground in a sea of mud. Getting the contractor to come back and reset the tank cost nearly as much as the initial installation.
Not all water storage tanks are designed alike, so the required modifications may differ, but the basic concept remains the same. The tank we used had five openings. Since for our purpose we needed only three, we sealed off the unneeded two openings with concrete ready-mix. Of the remaining openings, two were at the ends of the tank top. One would become our pipe chase, the other would accommodate a backup hand pump. The third opening, at the center of the top, was a large manhole — with a heavy concrete cover — which we use to access the tank for periodic inspection.
Since the manhole would be under 18 inches of soil, to improve access and also prevent surface water seepage, we surrounded the original manhole with a concrete collar extending four inches above grade. To keep soil, insects, and wildlife out of this extension, we made a second concrete cover. Both covers are heavy enough to be child proof, and in fact require a winch to lift.
An opening at one end of the tank houses the three necessary water pipes. One is the pipe that moves water from the well into the cistern. The second pipe moves water from the cistern to the pressure tank at the house. A third pipe serves as a combination overflow and vent — a precaution against excess water or air pressure building up inside the tank. The overflow lets surplus water run into a French drain (essentially a gravel bed), and has a T extension as an air vent. The vent ends in an upside-down U, to keep out rainwater, capped with a fine mesh screen to keep critters from crawling into the pipe.
To accommodate these pipes, before filling in the pipe chase with concrete we inserted pipe sleeves consisting of lengths of PVC pipe. Using sleeves the next size up from each pipe’s diameter easily accommodates the water pipes with no wiggle room for things to fall or crawl in around the edges. Around the pipe chase, we constructed a concrete collar extension reaching above grade and capped it with a concrete cover.
We wanted to include a water level indicator to warn us if the cistern is getting low. Electronic sensors are readily available, but we wanted one that would continue to work during a power outage. So we made our own. It consists of long, threaded rod with a toilet tank float screwed into the bottom, and is positioned to float freely without interference from pipes or the tank wall. It extends straight down into the tank through a length of ½-inch PVC pipe that was inserted into one wall of the pipe chase collar as the concrete was poured.
A red surveyor’s flag attached to the top of the indicator lets us see from a distance if the tank is full or if we’re drawing down water too fast. When the flag starts riding low, we look for a leaky toilet, or a faucet or hose inadvertently left open. Or maybe it’s just a warning that we did too many loads of laundry in a row, or watered the garden too extravagantly. Or maybe the well pump needs repair, in which case we start conserving water until it gets fixed. When the water level drops, the threaded rod is long enough to prevent the indicator from disappearing into the tank.
Water Storage Tanks: How They Work
Being experienced in plumbing and electrical work, we were able to make all necessary connections ourselves. Otherwise, we would have hired qualified contractors to make sure the system is hooked up right.
Basically, water storage tanks work like this: A submersible pump brings water up from the well into the buried cistern. The pump is triggered by a timer to pump water for a few minutes every hour. By adjusting the frequency and length of the “on” time, we found that pumping for 2½ minutes every 75 minutes keeps the cistern full with little overflow.
To prevent pump burnout, a Pumptec monitor shuts down the pump should a problem occur in the well. The Pumptec diagnostic lights indicate what the problem is — whether the well ran out of water before the 2½ minutes were up, which happens occasionally during summer dry spells, or the pump needs repair. Additionally, a Square D HEPD (home electronics protective device) attached to the breaker box safeguards the pump from power surges during our all too frequent lightning storms.
A pressure tank at the house directly feeds our household plumbing. When the pressure tank calls for water, a jet pump delivers it from the cistern. Although our typical household usage is 180 gallons per day, the system pumps about 300 gallons every 24 hours. Initially, the surplus water went toward filling the tank. Now it gives us the luxury of being able to do more than one load of laundry in a single day, water the garden, or even wash our truck.
When the power goes out, or if either pump fails, the benefits of using water storage tanks means that we still have water stored in the cistern to keep us going for the duration. To draw water from the tank, we installed a hand pump. It’s the next best thing to an off-grid water system to make sure we have enough water to get us through an emergency.
As a final step before filling the tank, I climbed down inside and cleaned out the accumulated rainwater, stray leaves, and work men’s footprints. Then we dumped in several jugs of chlorine bleach as a disinfectant, pumped the tank full, and let it sit several days to disinfect and to leach alkali from the concrete. After draining the initial water, we refilled the tank with fresh water, opened the valves, and let the pressure tank fill from the cistern. At last — we had water on demand! Self-sustaining living doesn’t mean you have to go without a decent water supply.
What kinds of water storage tanks have you used for your low flow wells? Leave a comment and share your stories with us!
Originally published in Countryside January/February 2015 and regularly vetted for accuracy.