Water Storage for Off-grid Living
By Parker Abercrombie and Art Ludwig
An ideal off-grid water system would draw water from an abundant, clean, year round spring or creek. There would always be enough water supply to meet demand, and there would be no concerns about extra water for fire protection or emergencies. But since few of us are blessed in this way, nearly all water systems include some form of storage, most commonly a tank. Even if you get your water from a municipal water system, you may want to store water at your home for fire protection or emergency preparedness. Water storage can be used to:
cover peaks in demand
smooth out variations in supply
provide water security in case of supply interruptions or disaster
save your home from fire
meet legal requirements
improve water quality
provide thermal storage and freeze protection
enable a smaller pipe to serve for a distant source
We’re going to consider each of these reasons to store water, then take a detailed look at water tanks, and a brief look at other ways to store water.
Cover Peaks in Demand
The most common function of water storage is to cover short-term use flows that are greater than the flow of the water source. For example, a tiny, one gallon-per-minute spring supplies 1440 gallons a day. This is several times more than most homes use in a day. However, almost every fixture in the home consumes water at a faster rate than 1 gallon per minute (gpm) while it is turned on. Even a low-flow shower head uses about 1.5 gpm.
By using water stored in a tank, you can supply water to the shower faster than it is flowing from the spring. On completing the shower, the water will be coming in faster than it is going out, and the tank level will rise back up.
If you had a 10,000 gal tank, you could run a 100 gpm fire hose—creating the kind of blast used to bowl over hostile crowds—on the stored water from this tiny spring, for an hour and a half! Hopefully the fire would be out by then, as the tank would take several days to refill.
Smooth Out Variations in Supply
In some circumstances, your storage needs will be affected by variations in the water supply. For instance, if the supply is rainwater, you will need enough storage to make it through the intervals between rainfalls. A six-month, rainless dry season requires a heck of a lot more storage than the most common kind of variable supply—a well pump that cycles on and off.
If you have a well that taps stored groundwater, a tank will save wear and tear on your pump, because the pump won’t have to switch on and off every time you open a tap.