Hidden Water In Your Home

The average single-family house holds somewhere between 50 and 60 gallons of drinkable water that is not in a bottle and not coming out of a tap. For a family of four that is most of a two-week supply, sitting in the building right now, already paid for.

Almost nobody knows the number for their own house. Find yours before you buy a single container, because it changes what you need to buy.

The water heater is most of it

A standard residential tank holds 40 to 50 gallons of potable water. It is the largest single source in the house by a wide margin, and it has a drain valve at the bottom designed for exactly this.

Getting it out safely takes four steps in a specific order.

Cut the power first. On an electric heater, switch off its breaker. Draining a tank with the element energized will burn the element out, which turns a water problem into a plumbing bill. On a gas heater, set the control to pilot or off.

Close the cold water inlet. There is a valve on the pipe entering the top of the tank. Closing it stops contaminated municipal water being drawn in behind what you take out, which matters if the reason you are doing this is a main break.

Open a hot tap somewhere in the house. The tank will not drain properly without air behind it, the same reason a can of juice glugs until you punch a second hole.

Then drain from the bottom valve. A garden hose fits it. The first flow often carries sediment and rust, which is unpleasant rather than dangerous. Let it clear before you start collecting.

Water that has sat in a heater is potable but not sterile, so treat it before drinking if the supply was already compromised.

Toilet tanks, not bowls

The upper tank holds clean water that has never touched the bowl. It is the same water that came out of your faucet, and there is usually two to three gallons of it per toilet.

One condition, and it is absolute: if you use an in-tank cleaner, one of the blue or bleach tablets that sits in the reservoir, that water is not drinkable. Do not use it for drinking, cooking or washing dishes. It is still fine for flushing.

The bowl is never a drinking source under any circumstances.

The pipes

There is water sitting in your plumbing, typically one to two gallons in a single-family home. Gravity will give it to you if you let air in first.

Open the highest faucet in the house to break the vacuum, then collect from the lowest one, usually a basement tap or an outdoor spigot. Without opening the high tap first, most of it stays where it is.

The rest

An ice maker bin is water. So is every tray in the freezer, and the ice is doing useful work keeping food cold until you need it.

Unopened bottled water in the pantry counts, including the case nobody remembers buying.

Canned food liquid is drinkable. Not appetizing on its own, and it is real hydration in a shortage.

A swimming pool is not a drinking source. It is enormous and it is chemically treated, and the arithmetic on making pool water safe to drink is not the arithmetic most people assume. It is excellent for flushing toilets, which is where the largest avoidable draw in the house lives.

Waterbeds appear on old preparedness lists. The water contains algaecides and plasticizer from the vinyl. Flushing only.

Do this before the tap goes off

Two things are worth doing on a normal afternoon rather than during an outage.

Find the valves. The cold water inlet on your heater, the drain valve, the breaker or gas control. Knowing which is which in daylight is the difference between a resource and a puzzle.

Fill the tub before the supply stops, if you get any warning at all. Storm tracks, planned shutoffs and boil notices usually give you hours. A tub holds 60 to 100 gallons, and a bathtub liner makes that water actually clean rather than tub-clean.

What this does not solve

Hidden water is a one-time withdrawal. It is not a supply, it is the head start you already own, and it typically buys a household somewhere between three and seven days depending on size.

Count it, then find out what that means in days, then decide whether to store more or use less.