Water Heater Question

[tn2]

When I bought my 28 ft Argosy about 7 months ago the water heater had a hole in the tank. In order to use the motor home I simply bypassed the water heater. I just installed a used water heater....which appears to be in great shape. My problem....... When I had the old tank bypassed...when I would turn the water on and then off.....the water pump would shut off almost immediatly. Now with the new (used) water heater installed...it takes a good 20 seconds to shut the water pump off. Plus....as the pump is getting ready to shut off....the pump start out sounding real soft....then as it gets closer to shut down the pump gets louder and louder. I think the problem of slow shut down of the pump must be due to the pump needing to bring pressure in the water heater up to system shut down pressure. Does anyone have a good cure for this. I've heard that some systems have an accumlator....would this help.
Any ideas would be appreciated.
Thanks
Charles

[TomW]

You have a water heater I would like to have.

I believe what you are hearing is the water pump working against an air bubble trapped at the top of the tank. The net effect is basically how an accumulator works.

I see no ill effects to your current situation.

I would like to have your tank because my tank does not trap any appreciable amount of air. The consequence is that, as the water heats up & expands, the excess pressure weeps out of my coldwater Over-Pressure Relief valve (OPD). If I had your tank, the excess pressure would compress the desirable air bubble you have.

No "fixes" are required for your situation.

Tom

[tn2]

Hi Tom
I kinda figured that was what was happening.....but it seems like there should be a way to trap that pressure inside the water heater tank. The way it is now...if you turn on the cold water the pump has to go through that whole noise process of re- pressurizing the water heater tank. Seems like a check valve would be appropreiate on the cold water in port to the tank. You would think that air that is trapped inside the tank would bleed off as you open the hot water faucet. When I first turned on the hot water faucet...I did get a lot of air. That doesn't happen anymore....I think that is normal. What I'm saying is that I really don't think there is a lot of air left in the tank.
Maybe it is one of those things we just have to live with. Oh how I would like to have back the sound of that nice quite running pump that I had before installing the water heater.

[Moonstruck]

I rather think it sounds like you have too much air in your tank. It's taking time to shut the pump off because the air takes longer to pressurise than the water would if the tank was nearer to full. You don't say which heater you have. I have the atwood and there are instructions for ensuring you have the right amount of air in the top of the tank which you should find in your product book. If I can help I will source mine and send a copy to you.
Marc

[tn2]

Thanks Marc

I too have an Atwood 6 gal tank but I bought it used so I don't have a manual with it....would appreciate a copy of yours. As the pump was filling the tank for the first time I just left the hot water faucet open. It spit a lot of air and then started running normal.....are you thinking that I still might have too much air. I tend to agree with you but sure don't see how I could get much more air out .
Thanks for your help
Charles

[Excella CM]

The amount of hot water you can get at one time will give you an estimate of the amount of water in the heater. Little hot water and a fast cycle time on the burner would indicate too much air in the tank.

[tn2]

The hot water comes out of a port that is almost as high as the top of the tank. Because hot water comes out immediately I would think there is very little room for much air. Now the RV is parked on kinda uneven ground so maybe air could hide in a high spot in the tank. To better discribe the noise the water system makes...so loud sounds like a cessna 150 landing. Starts out soft and builds up to loud noise. I'm sure it's air in the tank but how do I get it out.

[drag'nwagon]

tn2,

I replaced my water heater this year as well and up untill last weekend I had not filled it or used it by means of the fresh water pump. This season has been mostly camp grounds for us with water hook ups. I noticed the same issue with mine as you are experiencing, when the faucet was turned off the pump would continue to run and then slow down till it stopped and it seemed like an unusally long time (20-30 sec). To fix this I opened the pressure relief vavle on the water heater and wa la the air blew out and all systems went back to functioning normal. I was parked reletively level, but just a tad low on the curb side, which evidently was enough to trap a bit of air away from the outlet on the tank.
Give that a shot and let us know it helps.

[Moonstruck]

Originally Posted by tn2

Thanks Marc

I too have an Atwood 6 gal tank but I bought it used so I don't have a manual with it....would appreciate a copy of yours. As the pump was filling the tank for the first time I just left the hot water faucet open. It spit a lot of air and then started running normal.....are you thinking that I still might have too much air. I tend to agree with you but sure don't see how I could get much more air out .
Thanks for your help
Charles

Hi Charles,
find attached the instructions for obtaining the proper level in the tank. I also checked the troubleshooting for the pump but there are no symptoms which match your problem.

I hope this solves your problem but I also found a Atwood troubleshooting page - try this:
Atwood Mobile Products - Troubleshooting
Marc

[tn2]

Thanks so much to all for all the replies....I really appreciate it...nothing worse than guessing at something when you don't have a clue.
From the diagram it appears atwood designed the tank so there would be air in the top of the tank. Maybe I just have too much. I will try the relief valve to see if that lets out more air. Thanks for the suggestion. One thing I can say that's positive....this atwood heater really heats the water quick and it stays hot for long time after the fire goes out. I checked it over an hour later and water was still hot....and that was with the thermostat set about half way between hot and cold.