Safe to turn off our hot water heater when there's an unknown leak?

June 26, 2018 1:19 PM

I heard the hot water heater running and not stopping this morning so I called a guy in to check it out. Turns out that there's probably a hot water leak somewhere in the house, hidden either by walls or the floor.

His firm only does hot water system replacements, so the repair is not something he can take on. The leak is about 16 oz a min or so, based on the reading at the meter. We're on slab and I think I know roughly where the leak might be and I want to turn the hot water heater off until a plumber can come out to check it out. Can I do this safely? How? The internet only talks about what to do if there's a leak in the water heater itself and that's not our situation so I don't know if I should or not.
There's basically no way this is getting fixed today or tomorrow so chances are that it would drain and then be empty until it's turned back on. This seems like not a great idea, so we're leaving it on for the time being, but that means that gallons of water are draining under my house now.
Please halp. I could call him back but metafilter is friends.

posted by fiercekitten to Home & Garden (8 answers total)

Two parts here: electricity supply and water supply.

It is okay to turn off the electricity to the water heater and not the water supply, but not the other way around.

For electricity: the easiest thing to do is to flip the circuit off in your breaker box

For water: there should be a valve on the water heater itself that you turn
posted by slipthought at 1:24 PM on June 26, 2018

Do you know where the shut off valve is for your whole home? If there's a leak, that would be the easiest way to curb any water use while you're gone. Just turn it on when you need water, and then shut it off again at night.

I've had to do this, and it sucks, but it works. Many homes have easy-to-locate shutoff valves. Not me. There's one in the crawlspace, which is super tight. Or there's a shut-off by the street. We bought a plumbers tool and turn it off at the street.

If you have a neighbor who has the same style house as yours, they might know where the shutoff valve is. Or if you have the paperwork from your home inspection (pre-purchase), that might indicate where the shut-off is.
posted by hydra77 at 1:24 PM on June 26, 2018

You can turn the water heater off at the breaker, so it stops heating water. Turn off the supply to the water heater, and then drain the heater using a garden hose; there's a sillcock at the bottom for that purpose. It'll cost you, what, 60 or 80 gallons of water, but save you the trouble of finding the same water under your house.

16oz a minute is 7.5gal/hour, 180/day, which probably around 3 fills of your heater. Shut down and drain your heater. Go borrow a hose if you can.
posted by Sunburnt at 1:25 PM on June 26, 2018

Yes it's safe to turn them both off (as slipthought details). I would turn off only the water supply to the heater (and electricity of course) and then double check the meter to see if the leak has stopped. If not, try turning off other appliances. Good luck!
posted by Pig Tail Orchestra at 1:27 PM on June 26, 2018

I notice that everybody's assuming that the hot water heater is electric, but that doesn't seem to be specified in the question. The same rule applies to a gas one; shut it off if the tank is going to become empty. Turn the control knob past the "pilot" position, all the way to off.
posted by Larry David Syndrome at 1:47 PM on June 26, 2018

I forgot to mention, it is electric. I'll turn off the circuit breaker now so I don't drain hot water all over the driveway when I drain it.
posted by fiercekitten at 2:01 PM on June 26, 2018

Thinking more on this, it sounds like you know the leak is hot water, so you only need to turn off the supply line from the hot water tank.

You should see two valves on the hot water heater. If they aren't color coded red and blue, you can just feel them to see which is hot. That is the one you would want to turn off.
posted by slipthought at 2:07 PM on June 26, 2018

Hmm, I didn't know there's an outbound valve you can turn off; I never looked that closely at mine. If there is one, then I agree with slipthought that's it's a good idea, especially since it means OP can turn it back on to wash the dishes after dinner tonight or get the showers going tomorrow, and then turn it back off while waiting for service.

If not, well, drain the tank. And while you're at it, check its age, which should be on a sticker on the tank's side. Typical lifespan of water heaters is 8-10 years.
posted by Sunburnt at 3:40 PM on June 26, 2018