Maintaining air gap in new Atwood water heater

[Skipg]

I am familiar with the procedure of how to get an air gap in a RV water heater to prevent
pressure valve leak, but this new Atwood water heater just will not maintain the air gap.
Do you think it is A bad relief valve? Thanks for your feed back.

[CavemanCharlie]

BarneyS wrote:

4x4van wrote:
Snip... Air goes up, water goes down; where could the air go?

It gets absorbed by the water over time.
Barney

Ya, But, How much time ???

I keep my water heater full of water (but not always turned on) all summer long and have never had a problem.

[BarneyS]

4x4van wrote:
Snip... Air goes up, water goes down; where could the air go?

It gets absorbed by the water over time.
Barney

[4x4van]

30 years of RVing, 3 different RVs...never once had to "re-establish" an air gap in the water heater (and since I live in SoCal, I've never drained/winterized/refilled it either).

Seriously, it would be nearly impossible to "lose" the air pocket in the top of a WH unless there was a leak at the very top of the tank to allow the air to escape (or you park your rig upside-down:E). Air goes up, water goes down; where could the air go?

[opnspaces]

What is happening that makes you say the air gap is gone? Are you equating a dripping or leaking pressure relief valve to mean the gap is gone? If so my bet is on either a piece of something holding the valve slightly open, or a failing valve. I don't think a leaky valve can deplete the gap as the valve is lower than the bubble(check Chris Bryant's post above).

My relief valve weeps from time to time, typically I reseat it and the problem goes away. Try letting the tank cool and then open and shut the valve a few times. I guess the valve is replaceable as a last resort. But I would be concerned that the aluminum threads would come out with the valve.

[alfredmay]

An easy way to re establish the air gap is by injecting air into the water line. To do this drain the water from your water supply hose. Then re connect the hose to the water supply and to the RV. Turn the water supply on. Turn on a hot water faucet in your RV. Air from the hose will be forced into the water heater.

Every time you re connect an empty hose you re establish an air gap IF you open a hot water faucet first.

[Chris_Bryant]

[jplante4]

Ski Pro 3 wrote:
I've always heard the air gap in a water heater tank is what caused the valve to leak. Burp the valve and no more leak. At least, mine works that way.

Most likely what you're doing is just re-seating the valve. Unless you hold the P/T valve open until a solid stream of water comes out, you still have some air bubble in there.

We did the same thing in a steam plant. If a relief valve was jiggling a little during startup, we'd lift the seat and let it slam back down to stop the dribble.

Here's how it works.

[pasusan]

time2roll wrote:
For a permanent solution consider a small expansion tank.

Amazon - Shurflow

Expansion is an issue for closed systems. Mine would leak at the water pump fittings if the WH would heat a tank of cold water with no usage. Took a lot of time to eventually find the intermittent issue.

This is what I did. Our B has such a small water system that if I didn't let out some water at the kitchen faucet while water heating the relief valve would leak a bit. My manual (and the notice inside the door of the water heater) says that's normal. I just installed an expansion tank and so far so good.

[Ski_Pro_3]

I've always heard the air gap in a water heater tank is what caused the valve to leak. Burp the valve and no more leak. At least, mine works that way. Once all air is purged from the tank, the valve no longer leaks.
The only time it comes back is when I sanitize the system by draining and filling a couple times with chlorinated and plain water. Then I heat up the water, see it dribble, burp the air and let it cool down, then repeat. Second time; no leaks.

[time2roll]

For a permanent solution consider a small expansion tank.

Amazon - Shurflow

Expansion is an issue for closed systems. Mine would leak at the water pump fittings if the WH would heat a tank of cold water with no usage. Took a lot of time to eventually find the intermittent issue.

[Skipg]

Thanks I thought a bad valve was probably the problem.

[B_O__Plenty]

rk911 wrote:

Skipg wrote:
I am familiar with the procedure of how to get an air gap in a RV water heater to prevent
pressure valve leak, but this new Atwood water heater just will not maintain the air gap.
Do you think it is A bad relief valve? Thanks for your feed back.

well, I'm not. we're in year 33 of this RV thing and have never heard of a WH air gap. not being sarcastic...just wondering what the heck you're talking about.

40 plus years for us never heard of it either.

B.O.

[rk911]

tnks.

[jplante4]

The air gap is actually an expansion tank. Water being uncompressible will rapidly increase in pressure when heated. If there is no air bubble at the top of the water heater, then the water pressure will pop the P/T valve every time the burner or element kicks on. With the air bubble in the top of the tank, it just compresses the bubble. Re-establish the bubble by shutting off water to the camper, open the P/T valve and drain some hot water. Close the P/T valve and open things back up.

Skip - if the bubble keeps collapsing, I'd replace the P/T valve. The seat isn't holding.

Rich - you've probably never had to deal with this because you drain your water heater every fall, thereby re-establishing an air bubble every spring.