Rinnai tankless water heater issues with lg front load washer.

Discussion in 'Tankless Water Heater Forum' started by FRANKTORONTO, Mar 19, 2012.



    Mar 19, 2012
    I was wondering if anyone has this problem. Our LG front load washer pulses at the beginnning of the cycle as it spins to gage weight of load and fill required amount of water accordingly.
    When this pulses of water are released it places pressure on my Rinnai Tankless unit and it releases water from the pressure relief valve. I called the installer, he says it is a LG washer issue and that there is not much to tamper with in terms of pressure levels in the unit. I called LG and they say that releasing water from the sink beside the washer may help. It didn't, any ideas??
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    Turning water on and off should have no effect on the T&P valve of the heater. A T&P is normally set to relieve pressure at 150psi, and nowhere should that be approached. Not sure what a tankless uses, but it should be similar. What you may want to do is two things: first, check your static water pressure...if it is over 80psi, you need a pressure reduction valve to lower it and an expansion tank; second, a hammer arrester may resolve the problem if the pressure isn't too high. A hammer arrester is easy to install: unscrew the hose from one end - at the washer is best, screw the arrester on, then reattach the hose to the arrestor and you're done.
    Last edited: Mar 19, 2012
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  4. Hackney plumbing

    Hackney plumbing Homeowner

    Jan 6, 2010
    Install water hammer arrestors on both the hot and cold water valves of the washing machine. Water hammer can easily exceed 150 psi. M ake sure your static water pressure is not above 80 psi.
  5. RinconVTR

    RinconVTR New Member

    Sep 1, 2009
    You need an arrestor at the point of water connection for the washer, hot and cold. The open/closing of the solenoids during the start of a cycle create a very hard water hammer. Its not just an LG issue...most front loaders pulse water into the drum as it senses the load and begins a cycle.

    I've actually posted this issue before, but more so about tankless water heaters being useless with front load washers, in general. There is said to be a warming element in the LG for water temp purposes, but I have yet to find a written fact about this.
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