low hot water pressure/flow

[Titus]

Just got done de-winterizing. Opened the bypass to fill the water heater. Opened the water heater relief valve until water came out of it. Opened hot and cold faucet at both sinks to let air out. Normal cold water flow/pressure on cold side in both pump and city water mode, but low hot water flow/pressure in both pump and city modes. Opened and closed the water heater bypass valve several times to make sure that it was fully open. Opened and closed the hot water drain valves on both sides - and water drained out.

Only thing I can figure is bypass valve is partially closed even though it seems not to be or a piece of lime or calcium (or something) somewhere in the hot water line.

I have heater turned on (electric mode) to see if the low flow/pressure is at least hot water.

Any ideas out there???

[HowieE]

If you filled the heater at a fast rate of flow you most likely stirred up the sediment in the bottom of the tank and it has clogged somewhere.

Normally it clogs the the strainers at the faucet but in that case it would cut down the flow of both hot and cold. I can't think of any point in the hot water side that would clog. The bypass valve is before the heater so it is not there.

Not sure why you would open the relief valve while filling the heater. There should be an air pocket at the top of the heater to prevent the relief valve from popping when the heater is fired. Without that air pocket you would pop the valve more often than you want.

If the problem is not at the faucet strainers a possible repair would be to drain the heater and while the drain plug is out apply compressed air to a faucet with the strainer removed. That should push anything back into the heater. When refilling start with a slow flow as not to stir up the sediment.

[Titus]

HowieE
I removed the water heater drain plug and let it empty. I then took off the sink strainer (it was not plugged) and blew air back through it with the sink faucet open in the hot position. I could hear air bubbling when listening at the water heater drain fitting. I then reinstalled the water heater plug and filled the hot side slowly, letting the air escape at the sink valve. When the hot plumbing was full the water started coming out of the sink faucet, but still significantly slower than the cold side. Same with the bathroom faucet. It might have been a bit faster than before, but maybe that was just wishful thinking on may part. Like you, I am not sure when the plug could be, assuming that it is not at the bypass valve. The flow should be marginally enough to shower with - which is all that we use the hot water for anyway. So I will see if the problem solves itself in our three week outing that starts on Monday.

Unless anybody else has other ideas to try...

[rmkrum]

Some versions of the Atwood water heaters have a mixing valve on the backside that reduces the very hot water to reasonable by mixing in cold water. It’s done to get more hot water out of a smallish tank

If you have one, it could be silted up.

There was a recent thread on replacing/fixing one. Try a search on “mixing valve”.

[Titus]

Everything I can find on-line deals with temperature adjustment of the mixer. I will have to play around and see if my low-flow issue is really a temperature mixing issue. But I don't think it is, as I recall the hot and cold positions flowing similarly even if the heater is off. We'll see.

[BurntAsphalt]

Titus,
This is a long shot but I found some posts on another forum that some RV water heaters have a back flow preventer that fails and causes the symptoms you are describing. Not sure if the AI water heater has one but you might want to check. Good luck!

[Tom_T]

Originally Posted by rmkrum

Some versions of the Atwood water heaters have a mixing valve on the backside that reduces the very hot water to reasonable by mixing in cold water. It’s done to get more hot water out of a smallish tank

If you have one, it could be silted up.

There was a recent thread on replacing/fixing one. Try a search on “mixing valve”.

I'd like to find that topic too, since the new-ish Atwood in our `60 Avion T20 (2007-08 resto) also seems to be stuck or sticks after just a few seconds of running hot, then goes cold again, & it runs slow too. I cannot turn the adjustment nut/valve.

I can't find that thread with search on here nor googling for it, so if anyone has the link to it, please post here for the OP, myself & others with this problem.

Thanx!
Tom
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[greghoro]

Could be the hot water tank mixing valve.

See these links:

http://www.airforums.com/forums/f445...ml#post2081532

http://www.irv2.com/forums/f116/atwo...lve-65423.html

http://www.irv2.com/forums/f116/atwo...ir-105558.html


Greg

[tmwinn1]

Just had the dealership replace my mixing valve for no hot water. While boon docking at Bear Island I enjoyed cold showers in December when my mixing valve stuck in the cold mix position. I was able to get warm water later (109 F) after leaving Bear Island and traveling down 20 miles of gravel road. Jarred the valve maybe. Atwood states that I should get 120F at the tap. Additionally I have had the water pump cycle every 5 minutes for about a second with no visible leak, water flow was diminished too. Might all tie together but, anyway dealer replaced water pump for internal leak and low flow. Sorry, no answers here just observation.

[Titus]

Glad to hear that driving on gravel helped as my next step was going to be to tap on the valve with a stick, then a tack hammer, to see if I can loosen something. Then if that does not work I will try to backflow again, but this time with water instead of air. I think the water is more likely to dislodge something. From what I can guess the temperature adjustment, that is so hard to make, is unlikely to remove a piece of debris - if that is in fact the problem. In order to work on (remove) the mixer valve or look for a backflow preventer I will need to remove the rear seat, and I don't have time for that before we take off. Worst case we'll have to look for more commercial campgrounds (showers) than we would typically do.

[BurntAsphalt]

Originally Posted by Titus

Glad to hear that driving on gravel helped as my next step was going to be to tap on the valve with a stick, then a tack hammer, to see if I can loosen something. Then if that does not work I will try to backflow again, but this time with water instead of air. I think the water is more likely to dislodge something. From what I can guess the temperature adjustment, that is so hard to make, is unlikely to remove a piece of debris - if that is in fact the problem. In order to work on (remove) the mixer valve or look for a backflow preventer I will need to remove the rear seat, and I don't have time for that before we take off. Worst case we'll have to look for more commercial campgrounds (showers) than we would typically do.

Titus
After your trip if you get around to looking for the back flow preventers, they will likely be small silver or brass fixtures screwed into the tank's inlet and outlet.
Judging from the weather forecast, we midwesterners may have de-winterized too early. Hope you are going somewhere warm!

[MIFC]

We just had the same experience after dewinterizing when we reached our Southern destination. We removed the mixing valve and soaked it in some CLR for a couple of hours. It worked fine after that.

[Titus]

Tapped on the valve and it went from a little hot water flow to zero hot water flow. Removed the valve and didn't see any debris. It had a screen on the hot inlet side. Water seemed to flow through it but soaked it in CLR for a while. Couldn't tell any difference in flow after soaking. Reinstalled it and it worked. Thanks to all for your advice.

[Tom_T]

Originally Posted by greghoro

Could be the hot water tank mixing valve.

See these links:

http://www.airforums.com/forums/f445...ml#post2081532

http://www.irv2.com/forums/f116/atwo...lve-65423.html

http://www.irv2.com/forums/f116/atwo...ir-105558.html


Greg

Thanx Greg!

Now all I need is some time to work on it before the next trip, or to replace the mixing valve if the fixes don't work.

Cheers!
Tom
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[Titus]

An update: 4500 miles, eight showers, and six weeks later the hot water system is still working fine. In the future I will slowly fill the hot water heater to try to avoid flushing debris into the mixing valve. And if that doesn't work I will again remove the mixing valve and flush it with CLR.