I installed a new Atwood GEH9EXT water heater in our coach a couple of weeks ago replacing what I believe to be the original Atwood water heater. I have a couple of issues but will only discuss the pressure relief valve in this thread.
Twice I've noticed water on the ground underneath the bay that holds the water heater. When I open the bay I see water accumulated in the bay, on the lower lip of the water heater and the first time I noticed a drop of water on the pressure relief valve which leads me to believe the pressure relief valve is activating. Anyone have any idea why it would be activating? Is the water getting too hot causing too much pressure? Maybe a bad pressure relief valve? The original never activated unless I turned the lever to test it. I looked through the manual but don't see any mention of a way to adjust the water temperature.
I'll call Atwood later today when I get some time but wanted to ask the wisdom of the group first.
see ya
ken
Not only is the relief valve activated by pressure, but also by temperature. I had one start leaking when water got warm and stop leaking after water cooled.
PRESSURE-TEMPERATURE RELIEF VALVE
Weeping or dripping of a pressure-temperature relief valve while the water heater is running DOES NOT mean it is defective. This is normal expansion of water as it is heated in the closed water system of a recreation vehicle. The Atwood water heater tank is designed with an internal air gap at the top of the tank to reduce the possibility of weeping and dripping. In time, the expanding water will absorb this air. To replace the air follow these steps:
Step 1: Turn off water heater
Step 2: Turn off incoming water supply
Step 3: Open the closest hot water faucet in the coach
Step 4: Pull handle of pressure-temperature relief valve straight out and allow water to flow until it stops.
Step 5: Allow pressure-temperature relief valve to snap shut, turn on water supply and close faucet.
Atwood Water Heater Troubleshooting (http://www.beamalarm.com/Documents/atwood_water_heater_troubleshooting.html)
There is a good article on water heaters in the May, 2012 issue Family Motor Coaching (FMCA magazine). Very thorogh (painfully so!). They make the same point about the relief valve.
Another leak I have had in our water heater is from the plastic drain plug. In my experience these deteriorate and leak with age. I installed a brass plug and that stopped the problem. However, these tanks are made of aluminum which is more reactive than brass. The FMCA article recommends against using brass plugs (and anodes). However, I checked with Atwood and this is the response I got this morning.
"Brass is ok to use. Some manufacturers use brass check valve fittings on the back side of the water heater for the water line hook ups as well."
So, I am going to stay with the brass. Leaking water in this area is not good due to its proximity to the rear bulkhead.
I have given up on keeping the plastic drain plug from leaking. My solution ( Think red neck ) is to cut the side out of a SPAM can and fit it under the plug. The little drip has never filled the can and each trip I simply take the can and dump the water out til next time. ( doesn't every one have a a spare Spam can in the coach )? :)
Gary B
Ken,
I believe you still have your accumulator tank above the water pump? You may need to check the air pressure or add a little more. I had the same weeping pressure relief valve issue when I got rid of the accumulator tank (because I got a new variable speed pump). The "air gap in the tank" procedure didn't work all the time. When I added back an accumulator tank the weeping pressure valve problem went away. BTW, this is more of an issue when the temperature difference between incoming and heated water is larger (i.e. winter).
Thanks Barry! Seem likes Atwood could have included that information in the documentation! That diagram really makes it easy to understand the air gap.
I've run through the procedure. Hopefully that fixes it. I'll be keeping a close eye on it...
George & Gary I haven't seen any droplets from the drain plug yet but I'll keep a spam can close at hand just in case. :D I'm not one to turn my nose up at a simple red neck solution!
John I've removed my accumulator but thanks for the input.
The whole pressure relief design on the Atwood is pretty crappy. Seems like you would want to dump the water outside the coach not just spray it into a bay! Hmm... I guess spraying it into the bay kinda forces you to take action instead of just blowing it off. :) That reminds me of the Tappit brothers on car talk. They suggested that car manufactures should replace the engine warning light with a dollar amount indicator that gradually increased the longer you ignored the warning! Love those guys.
see ya
ken
We have a two year old Atwood hot water heater. When we installed the new tank, I ran a hose from temp-pressure relief valve down through the floor with the other three drain hoses.
Our valve will open from high pressure caused by heating cold water which caused quite a bit of expansion on the whole cold and hot water systems. We find this large increase in pressure is reduced by keeping our hot water tank on most of the time.
We usually keep our electric heating element on most of the time to reduce wide swings in pressure. We have a pressure gauge in our plumbing system and see over 120 psi during hot water heating, which can stress our plumbing, so it benefits us to keep our pressures down by short openings of our faucets when heating cold water.
We have spare Atwood plastic drain plugs and use sealer on the threads after removing the plug to drain our tank every couple of months. Draining always removes cloudy water and any white sediment in the Atwood tank.
Hmm. I think an accumulator in the system would mitigate the pressure issues. Even a small accumulator might allow enough air space to absorb the changes in volume as the water heats. The air in the accumulator is much more compressible than water. I would expect an accumulator to provide the same benefits as the air space in the water heater that Atwood recommends.
I am not aware of any check valves in the fresh water system that would interfere with an accumulator serving as a pressure/hammer mitigation device for the entire fresh water system.
We changed to a water pump that doesn't require an accumulator, but left the OEM style accumulator in the system. The new pump with accumulator works very well.
@Barry I'm intrigued by your hose to divert the water out the bottom of the coach. How did you attach the hose and route it? Any chance of a picture?
Oh and thanks for the heads up on the pressure build ups. I fill my fresh water tank and use the pump to deliver water on board. Assumed that protected me from high pressure in the lines. I'll have to reevaluate that!
see ya
ken
Barry's hot water tank pressure relief valve hose discharge intrigues me also. I believe that the idea is to prevent any water from pressure build up from entering the cabin floor area. Would be interesting to see some pics.
As to filling the tank and running off the tank, when I am going to be at a campground for a while, I do not fill my tank or use my pump, but turn off the tank valve and run off the campground's pressure. When traveling I half fill the tank and run off the tank while "on the road" like between up state NY and Florida. When I arrive at the campground in Florida, I hook up the city water and turn off the tank, and drain off the tank. When leaving that campground, I fill the tank up to half full again, prior to unhooking the city water. I may end up changing my procedure because I have added a water softener to my system and from now on all the water going into my coach will go thru that water softener, but doubt I will have to change anything except for placing the water softener on line when hooked up to outside water for any reason.
Here are photos of our hot water tank temp/pressure drain hose. . .
Thanks for the pics Barry. As usual excellent work! Is that a washing machine hose?
I guess I'll heading to the hardware store now...
see ya
ken
Yes that is a washing machine hose with the other end cut off.
A leaking safety valve to me not exceptable . If the valve on my hot water tank at home was leaking I would replace it,not just divert it to a drain. The hot water system in a motor home is a small system and needs an accumulator tank that is working ,not water logged ,and that is set for the correct pressure. If the safety valve leaks its is bad, or the pressure is to great, or the water temp is to high. Gam
Gam, If the system does not allow for expansion a new valve will also leak. When the heater heats the water it expands and if there is no accumulator tank, air trapped or flexible hoses that will expand the valve will open as it should. If the valve has opened many times it may fatigue or the spring will rust and it will require replacement. It should also be noted that the higher the temperature setting on the thermostat the more expansion and the more likely the valve will open.
That was the point . With a back flow preventer on the system the pressure can build to 120 lbs and the safety valve will open. The way to prevent this is to install an expansion tank in the cold water line before the hot water heater. If not your entire system can have 120 psi on it , and the only thing preventing more psi is the safety valve and that's not a good thing. Gam
That sounds like a good idea... right now I have the entire utility compart bare as I finish up the basement frame rebuild, and there would never be a better time for me to do this project than in conjunction with installing the new water heater, water pump and accumulator, associated pulumbing and drain valves etc.
Any links or pictures of an expansion tank installation?
Thanks, Don
on line check how to install expansion tank on hot water heater. It's now code for most homes. A 2 gallon tank is more then large enough , and can be teed off the cold water line and remotely located. Gam
You can put the tank anywhere in the cold water circuit. When I re-installed my expansion tank, I put it under the kitchen sink where I had an unused corner. This leaves the water pump area much roomier for service. I connected the tank with a flex hose - fitting pointing down for winterizing.
Great point! On many coaches there is a significantly sized unused area forward of the sink, behind the drawers\icemaker. Perfect for something like this
I put mine in the area the washing machine was, just used the existing washing machine plumbing.
I think some of the trouble with safety valves is the number of pump accumulators that have been removed or are not working. The accumulators are small but the expansion of water in the hot water tank is only about .16 gallons. The safety valves will start leaking by if they have to vent even this small amount of water over and over again. As for having a small amount of air in your tank so that there is room for expansion. That will work for a short time, but with flow through the tank the air will mix with the water and be lost and you will start popping the safety valves again. Gam