Hot water heater purge issue

MarkoPolo · 04-17-2013, 01:35 PM

We took our new 2922KD out for it's first camping this last weekend. What a great upgrade from a tent pop up!
I had a strange issue with the water heater/water pump. We did have shore power but no water. So, I filled the 20 gallon tank and opened all the hot water faucets to purge the air. Everything is working fine.
The next morning the water is at a trickle and I hear the water pump running. So I figured that I really didn't completely purge the air, so I again opened the hot water, got air coming out and even opened the pop off valve of the water heater to purge some more. Added more water, everything works properly.
That night I wake up hearing the water pump running. Again water turn on reveals only a trickle. So purge the hot water faucets, water pump stops.
The next morning, same thing happens again. I add water, purge the hot water lines and carefully check to see if water is leaking somewhere under the trailer. Working normally now. It's the only thing I can think of that might let air get in the hot water heater!
At any rate, found no leaks. By now it is time to go home. I call The Car Show and Will has never heard of anything like this. I know it doesn't make sense to me either. The only thing I can think of is that I have not purged the air properly or completely.
I intend to put up the camper in the yard and try all this again as soon as the snow melts, but thought the forum would be a great place to see if anyone else has had a similar problem. Thanks in advance.

HIKERZ · 04-17-2013, 07:25 PM

Could it be that your supply had some debris

04-17-2013, 07:37 PM

Purging the HW tank to get sufficient water to protect the element is one thing. That is adding enough water to the HW tank to to submerge the element and keep it from burning up. You need to let the water ( including cold) run a while to get all the air out of the lines to keep the pump happy. That includes the cold water. The other possibility is that the pump is drawing in air with the water due to a loose fitting. The air will compress and the pump will run. Try purging the hot and cold water at the faucet the longest distance from the pump.

ZekenSpider · 04-17-2013, 08:24 PM

Quote:

Originally Posted by MarkoPolo

We took our new 2922KD out for it's first camping this last weekend. What a great upgrade from a tent pop up!
I had a strange issue with the water heater/water pump. We did have shore power but no water. So, I filled the 20 gallon tank and opened all the hot water faucets to purge the air. Everything is working fine.
The next morning the water is at a trickle and I hear the water pump running. So I figured that I really didn't completely purge the air, so I again opened the hot water, got air coming out and even opened the pop off valve of the water heater to purge some more. Added more water, everything works properly.
That night I wake up hearing the water pump running. Again water turn on reveals only a trickle. So purge the hot water faucets, water pump stops.
The next morning, same thing happens again. I add water, purge the hot water lines and carefully check to see if water is leaking somewhere under the trailer. Working normally now. It's the only thing I can think of that might let air get in the hot water heater!
At any rate, found no leaks. By now it is time to go home. I call The Car Show and Will has never heard of anything like this. I know it doesn't make sense to me either. The only thing I can think of is that I have not purged the air properly or completely.
I intend to put up the camper in the yard and try all this again as soon as the snow melts, but thought the forum would be a great place to see if anyone else has had a similar problem. Thanks in advance.

I'm thinking there is a problem with either the water pump inlet or outlet check valves. When the pump runs it pulls water from the water tank and pushes it through the Hot and Cold water lines to the faucets. The pump keeps running until the faucets are closed causing pressure to build-up in the lines. As the pressure builds up, a pressure switch in the pump shuts the pump off. It waits for the pressure to drop, then restarts the pump to build the pressure up once again.

If there are no leaks downstream (faucet side) of the pump or at the pump check valves, the pressure stays up and the pump does not run. It is possible that dirt on the pump check valves is allowing water to leak backwards through the pump into the water tank which makes the pump run again. If this is happening, it should show up as water leaking into the water tank when "shore water" is connected, the pump is off and the water tank is empty.

Just a thought,

Jerry

PS Attached find TM Plumbing diagram

MarkoPolo · 04-17-2013, 08:59 PM

Thanks for the replies. Bob, I was running the hot water heater on propane, not electricity. Not sure if the element being covered is applicable. Jerry, thanks for that info. I did not know how the check valves worked. That might be a plausible explanation. Hikerz, I have not emptied the water tank before we left, so there might have been debris there.

04-17-2013, 11:08 PM

Not sure this will be helpful, but when I installed a deck lid on our water tank I was surprised with the amount of stuff inside. Thought it would be clean, but there was some plastic inside, probably left from drilling. Could have made a mess of the pump had I used the pump before I cleaned out the tank.

**ShrimpBurrito** · 04-17-2013, 11:25 PM

Did you purge the cold water lines also?

Dave

ThePair · 04-17-2013, 11:58 PM

Gaskets dry?

If it's the first outing, it's possible. Just now I put water into my system, and the kitchen sink faucets decided to leak a little water out under pressure, at least until the gaskets in the faucets got a little wet. I think it's stopped now.

I'd keep an eye on it, but if it doesn't happen anymore, I'd venture a guess that that's the culprit.

04-18-2013, 06:40 AM

The thing that is strange is that the pump goes off when you purge the system but then by the net morning it is on and if I read right it stays on. A small leak on the pressure side or debris in the back flow valve would cause it to cycle on but once the pressure came up, it would shut off and them recycle again. It is possible there is debris in the pressure switch preventing it from seeing the actual pressure in the system and thinking it was in demand mode. Purging would release pressure enough to momentarily clear the system as would any high water demand, however slow drop in pressure overnight might not. It could also just be a sticky pressure valve which would do the same thing. During your testing when it gets stuck on after not being used for a while try tapping the pump housing lightly to see if the sensor will activate.

thewayneo · 04-18-2013, 08:50 AM

Hi Marko--it sounds like you are well purged. Like Rumbleweed, I would zero in on the pump. Check the inlet side fittings between the tank and pump to make sure they are tight, not sucking in air.

Last year I swapped out the original pump for a quieter one, but saved the old one "just in case." If you don't find another cure, I could run up to Greeley and we could do a quick swap, see if that fixes the problem. Right now I'm trying to get in some final camping trips before the snow is gone, but anytime after that.

You can pm or email me.

wayne