water heater leak

[John Dirks Jr]

I was checking my parents house out while they are out of town. I found the water heater leaking. It's an electric model circa 1979 so yeah, it's shot.

The WH breaker was turned off. I turned off the main supply (house), opened all the hot at the fixtures and used a hose to drain the tank out into the yard. After that I closed the isolating valve at the water heater and turned the main (house) back on. For some reason, whenever the house supply is on, water trickles back into the tank even though the isolator valve at the WH is tightly closed. I figure one of the following;

1. The isolator valve at the WH is not completely closing off the supply.

2. One of the delta style faucets is not functioning right and allowing water from the cold side to bleed back into the WH. Actually, I'm not sure if they are delta style as Im not sure what they are called. They're the kind where you have one knob that you pull out to turn on and turn left to right for hot or cold. What style are they called? Could one of these have an internal leak that allows water to bleed back from the cold side and into the WH?

I was trying to leave the house in a state where at least the cold water was working. However, I cant get the WH isolated for some reason. Whats going on here?

[smarcus]

I think you're looking for mixing valve. If you turn on the mixing valve with the cold supply on, the water can travel back down through the hot supply lines.

[John Dirks Jr]

I think you're looking for mixing valve. If you turn on the mixing valve with the cold supply on, the water can travel back down through the hot supply lines.

Aren't those pull and twist faucet fixtures a mixing valve of sorts?

[John Dirks Jr]

Here's one of sorts. If this thing is malfunctioning internally, could it let water bleed from cold to hot when in the off position? Thereby, even though a WH with the isolator valve closed, could still fill back up by water draining down through the hot line?

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[Erby]

Several styles similar to that can let water bleed back into the hot line, though they shouldn't be doing it when the valve is OFF. Sounds like you need to cut the line feeding back to the water heater and put a valve on it also.

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[John Kogel]

Thanks, John, Now I know why I sometimes see a shutoff on the hot side of the WH as well as on the cold. []

You said you opened all the hots. Did you turn them all off?

A plumber was changing out a water heater in a condo building yesterday. He brought the old tank downstairs in the elevator, still full of water. Too hard to drain it in the apartment, or too slow. Well I guess the drain tap wouldn't shut off after he'd played with it. So he left a stream of rusty water down the hall to the elevator and then out the main entry door where he parked it to bleed out into the storm drain. Left a puddle of rust there, then a smaller trail out thru the parking lot to his truck.

The good part was he left the main doors propped open the whole time, so I was able to poke around the building before the keys arrived. He also forgot to close the doors when he left.

[Jim Katen]

It's probably the isolator valve at the water heater that's leaking. I've had to deal with that exact problem a few times.

Just shut off the main valve for the whole house when you replace the water heater and while you're at it, install new high-quality valves at the inlet and outlet for the new water heater.

You are going to get all this done before they return, right?

[John Dirks Jr]

Thanks for the input everyone.

I have the leak stopped and the water mess vacuumed up. Parents are aware of the situation and planning to get a plumber in there to handle things. There's also a bad kitchen faucet and a leak in the drain pipe under the sink.

I could do it all if needed but I'm so busy with lots of other stuff and they understand that. Also, they like to give employment opportunities to people and they can easily afford to have local contractors fix stuff when needed.

They were happy I caught the leak and was able to minimize damage.