Forum Discussion

MrVan's avatar
MrVan
Explorer
May 07, 2014

Lost Hot water pressure

On our last trip on the return side the water pump quit providing adequate pressure even though it ran normally, but would never shut off. Finally got around to trying to figure out what is going on. tried the pump again at home and noticed I wasn't getting any pressure at all on the hot side and very low pressure on the cold side and the pump never quit running. Decided to drain the suburban water heater, pulled the anode which was completely used up and a whole lot of the white residue was in the tank. Flushed the tank several times as best I could, got a lot of white stuff out, way more than normal. This anode has been in there for 5 months of continuous use in AZ before the last trip home. The RV has been hooked up to city water for 5 months prior to the return trip. Ok, cleaned the anode up and re-installed it and hooked up to city water again and waited for the water heater to fill back up. Still no hot water pressure but normal cold water pressure. Disconnected the city water and tried the pump. Pump wouldn't even turn on???? That is weird. Hooked back up to city water and tried the pump just out of curiosity and it ran again. Now that is really weird. But the bottom line I'm not getting any hot water pressure either with the pump or from the City water connection but decent cold water pressure with both the pump and the city water connection.

I'm offering all this information even though some of it doesn't make any sense yet. My present guess is some of the white residue off of the Anode has plugged the out hot water line somewhere. I have no idea how this 2006 Keystone/Montana 3400RL is plumbed but my thinking is it must be plugged on the outlet side of the water heater feeding all the hot water taps. I don't know if I have two problems or just one. I don't understand why the pump doesn't shut off even if one pipe is plugged somewhere. I've initially tried to blow air pressure back through the hot water side of the kitchen sink faucet but that hasn't helped. I didn't seem to get any relief blowing backwards which I kind of expected and that confuses me. I expected that air pressure to show up in the water heater. Ran out of daylight. I think I will try putting back air pressure from the two other hot water taps as well to see if that unplugs the main line from the water heater that must feed all three hot water faucets. Am I correct that the 12V pump just feeds cold water pressure to the water heater similar to the city water connection and the hot water gets to the three hot water faucets the same way no matter whether I'm on the pump or the city water connection? I would think it would have to be plumbed that way. I suppose I could have a broken hot water line but I don't see or hear water running when all faucets are turned off and none coming out from the bottom of the RV. Is my thinking correct that this has to be caused by a broken, plugged or twisted Pex line from the water heater to the three faucets? Looking for other hints and tips on how to isolate this further. Not going to try to troubleshoot the water pump further until I get the hot water running properly on the city water connection. The two problems may be being caused by one issue but It doesn't make sense to me yet. Any tips or hints would be appreciated. Help???
  • MrVan's avatar
    MrVan
    Explorer
    Jun 01, 2014
    Installed the new hot water heater outlet check valve
    All is now working properly. The little tab that provides a stop for the spring had fallen off the old one. Tried to see if there was a way to get it to stay on
    No luck. Bought a new Marshall Gas Company brass check valve identical to the old one. However I must have not been the only one that had the tab come off
    the new tab is a slightly different design. Thanks for everyone's help
  • MrVan's avatar
    MrVan
    Explorer
    May 27, 2014
    Finally found the time to remove the water heater outlet one-way valve. It was a brass Marshal valve G784 with 1/2" male threads on each end. The internal check valve made from nylon? or plastic had completely come undone and the little holder opposite the actual valve end had come off and was loose in the water heater fitting after I removed the brass assembly. Luckily was able to fish it out of the water heater fitting. So I'm 99.99% sure I've found the problem and I think I've found the correct replacement on eBay. None of the flaky material from the anode I found in the Water heater was in the valve seat area. The valve just came apart. Thanks for the help.
  • MrVan's avatar
    MrVan
    Explorer
    May 09, 2014
    Thanks for all the good info folks. When I get my outlet valve changed I'll get back on here.
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    May 09, 2014
    MrVan wrote:
    Maybe someone could explain to me why everything other than the bypass function now seems to be working properly. I'm assuming that one of the one way valves has switched positions due to be turning on the bypass valve. But I don't understand why the pump wouldn't turn off unless it was just recirculating water???? And if one of the one-way valves has changed positions why am I getting water in the water heater when I have it bypassed. Its not sealing well in the opposite position it was in? Some junk in the valve? Going to open up the out hot line and check the one-way valve but I'm trying to understand this a little better.


    WHen you use the bypass.cold water goes to hot water line 'bypassing' the water heater.

    BUT if the check valve in hot outlet is jammed/stuck/clogged water can go back into water heater from the hot out.
    The check valve is suppose to allow hot water out and close to stop backflow.

    When crud is in check valve (or check valve failing) it can stop good flow of hot out and/or allow water back in

    I don't have ANY check valves on my water heater.

    I have 3 valves......cold inlet/hot out/bypass
    When I bypass the WH....cold/hot are closed and bypass open.....no back flow and no relying on a cheap plastic piece of junk check valve.

  • MrVan's avatar
    MrVan
    Explorer
    May 08, 2014
    Maybe someone could explain to me why everything other than the bypass function now seems to be working properly. I'm assuming that one of the one way valves has switched positions due to be turning on the bypass valve. But I don't understand why the pump wouldn't turn off unless it was just recirculating water???? And if one of the one-way valves has changed positions why am I getting water in the water heater when I have it bypassed. Its not sealing well in the opposite position it was in? Some junk in the valve? Going to open up the out hot line and check the one-way valve but I'm trying to understand this a little better.
  • MrVan's avatar
    MrVan
    Explorer
    May 08, 2014
    New update. Now I am back to having both hot and cold water pressure with both the city water connection and the water pump. And... the water pump shuts off when it reaches desired pressure. Might think things are all working again but.... need to try the winterizing valve and see if that mode still allows water into the water heater. If that is true I probably have a one-way valve sticking on the outlet side of the water heater tank.

    Thanks for the water piping schematic, I had uncovered it when I did a search on RV.net previously. Thanks. It doesn't show the one-way valve on the water heater tank outlet but I now know where to look for it. I hope it is easily accessible. When I had to replace the Water Heater control module a couple years ago it was a really tight spot. Maybe there is another way to get to the back end of the water heater. I hope so.

    I usually flush the water heater and change anodes at least twice a year but this year was the first time the 5th wheel was occupied for 5 straight months in AZ. I can see that when that much of the hard AZ water passes through, the Anode probably needs to be changed more often and the heater tank flushed more often.,

    PS: I don't recall ever switching the bypass winterizing valve before in the seven years we have owned the 5th wheel. I have always just drained everything and blew out the lines to winterize. Don't usually have to winterize since the RV spends its winters in AZ. 7 years and still learning new things about this 5th wheel. Sure glad I didn't start trying to fix this by replacing the water pump. :-)
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    May 08, 2014
    On the backside of water heater top line (hot out).....disconnect hot line.

    Inside the fitting that is screwed into tank is a check valve.
    It is plugged.clogged/jammed shut from all the calcium/stuff from AZ Hard water

    You probably will need to replace it.

    You also need to drain/flush water heater more frequently.....especially when using hard water (AZ, NM, TX, S/E CA, etc.)
    Anode rod doing it's job...protecting WH Tank. But in doing so is dissolves plus the crud from the hard water.

    And YES......city water and pump discharge are tied together. So both feed everything cold/hot.

    Basic RV plumbing system.

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