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Water Heater Backflow

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  • Water Heater Backflow

    I've recently had calls that involved the sediment from water heaters plugging pipes and faucets. One was the more obvious trailer house type with the bottom fill. We have a lot of sediment in the water and in the case of the bottom fill, the lime chunks had carried all the way back through the trailer and out into the yard in the direction of the pump house.

    So what's happening is that, when the water expands, sediment is carried back into the cold water line, and each time is moved further along.

    I also had a house recently with a top-fill water heater and only a single fixture was plugged. That customer has called before for the same problem, but refuses to go any further to prevent it.

    So my question is: is there any preferred method of preventing this problem? I'm thinking that a combination of check valve and expansion tank might work, but on a bottom-fill trailer where the tank is accessed from outside, it might be a trick to install an expansion tank. Would it be better to loop the incoming cold water pipe high above the heater, put the expansion tank there, then the check below that? Or is there some device that would work better in this situation?

  • #2
    Re: Water Heater Backflow

    Herk, are you saying the cold water backs out of the tank and into the cold water line. If so there's something funky going on here. I.E. there is somehow more pressure on the tank side than the inlet.? A backflow preventer would solve that problem, but I'm afraid the pressure on the downside would cause the relief valve to pop. And that does not really get to the root problem. Do a bit more investigating I'd say.


    • #3
      Re: Water Heater Backflow

      Why don't you just put in a swing check in before the expansion tank? you can put the expansion tank anywhere on the line between the swing check and water heater
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      Last edited by TOPDAWG; 02-24-2011, 04:47 PM.


      • #4
        Re: Water Heater Backflow

        Herk, I run into the same problem with the bottom fed water heaters about once a month in my town. Don't waste your time with check valves and expansion tanks. Get them to let you replace the water heater with a top fed water heater and to then flush out all the cold water lines. It is an expensive job, but in my opinion is the best way to guarantee that the problem will not happen again. The warranty on most of the bottom fed water heaters is only one year, compared to a new top fed water heater with a six year warranty. All the mobile homes I am in that have this problem are all over nine years old. With that much sediment in them already, that water heater is on borrowed time.


        • #5
          Re: Water Heater Backflow

          To all:

          Keep in mind that we have a LOT of sediment here. It's not uncommon to find a water heater a third full of calcium salts that have dropped off the elements. Sometimes, the chunks are so big they won't fit through the 1" element opening. It's not a matter of a simple flush.

          Also keep in mind that the water heater in a trailer situation is in a very limited space - any tank would have to fit above the heater, since there is no room alongside.

          As water heats, it expands and has to go somewhere. In the case of the trailer, it can only expand into the cold water line in the direction of the pressure tank out in the pump house.

          And one more thing to keep in mind - I've had similar problems with top-feed water heaters, though not quite as bad. Water can expand up the dip tube and carry this junk with it.

          If I had to replace the heater every time this problem occurred, I'd be replacing most water heaters every three years. That's a lot of landfill. (So far, my own Rheem has lasted about 7 years or more without a repair . . .) I once had a 1-year-warranty heater that I got cheap, and I had to clean it and replace the bottom element once a year.

          I'm thinking that, in the case of the trailer, the combination pipe loop over the heater, expansion tank, and check valve would work. At the very minimum, a loop of pipe would greatly reduce the problem. The average sediment cleaning takes about an hour and a half or more. It's irritating when the customer is so cheap all they want is to have the plug fixed and won't even spring for heat trap nipples.