Where's da water going?

[Bob]

Ok, I have a cabin in the country. Because the propane WH is getting close to being old, when I'm not going to be there for a week or so I turn the water inlet valve off and the thermostat to pilot. That way if it leaks, the water spilled will be limited to 40 gallons. Anyway, when I turn the water valve back on after a week or two, there is a good amount of air in the tank and hot water lines. There is no water around the heater. There is no indication of rust on the tank burner or tank bottom. I crawled under the cabin and there is no water spotting on the subfloor, nor water on the vapor barrior. So I'm puzzled. Where is this air in the tank coming from? I'm talking about air/water spewing for up to a minute. First thought was a leak and second thought was volume contraction due to cooling. But that much???

Bob

[Charlie Morgan]

I've been going to your cabin and taking water out of your water heater.

CWM

[George]

Cooling water heaters suck It's probably "sucking air" when it's off. For a demonstration try this fun experiment, get an empty gallon plastic milk jug and put a 1/4 cup of water in it, now stick it in the microwave (with the lid OFF) just long enough to get the water good and hot, now take it out and screw the lid on and let it cool off (you can set it in the fridge if you want fast results)....see what happens to the jug?? Cool huh? When your water heater cools it does the same thing...only it is stronger than a plastic jug.

George

[Bob]

Ok, I can buy that. But with the faucets closed, where's the air coming from, the pressure relief valve backflow? And where is the water that is replaced by air going?

[Joseph Meehan]

I would guess either the PR valve or the air could be coming from the water. Water does absorb air. How much air depends on the temperature and pressure. Have you not noticed that sometimes when you fill a glass with water (during the winter) it is milky looking. That is air that was in the water. The time of year and the change in temperature of the water may be forcing dissolved gasses.

[mm]

I have your water. You can have it back for 3000 dollars in small bills.

[trainfan1]

Try your experiment with a full jug(water heater). The results will be different.

Rob

[HeyBub]

Faucets are optimized to prevent stuff from going in one direction, not the other.

The suckage may be much greater than normal water pressure anyway.

[Bob]

A good possibility. First water flow is somewhat opaque, then clears. I never thought to relate it to air in the water. Would also explain why the total volume in the tank wouldn't change. Sounds like the best explaination yet - even better since it doesn't relate to a problem. (I don't think). Bob

[Bob]

But how can it suck air into a tank that is full of water without forcing some of that water out somewhere? Wouldn't there have to be much less pressure inside the tank than outside? Since liquids cannot be compressed, there would have to be air already in the tank for a pressure differential.

[Lou]

Which do you do first, turn the main on and then open the faucet? or Open the faucet and then turn the main on?

[whatever]

Hi Bob

Do you have an anti siphoning device on your water heater? This can occur without one, either naturally or when work is done on the lines. Around our area it's a standard item to have.

Regards Dale

[Red]

No. But I don't see how it could siphon with the inlet valve closed. That'd be like a finger over one end of a straw.

[Red]

Does it either way. With the main on first, you can hear water entering the tank so the air is in the tank prior to any valve being opened. The more I think about it & discuss it, I'm leaning to air in the water as it enters the tank, then separating as it sits. Water comes from a saturated sand aquafir so I can understand how water movement down there could induce air into the mix.

[Bob]

OOPS, used my alternate logon. Sorry. Bob