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Thread: Rinnai R50lsi low hot water pressure.....

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  1. #1
    DIY Junior Member
    Join Date
    Apr 2010

    Default Rinnai R50lsi low hot water pressure.....

    Hi just installed another Rinnai tank-less hot water heater. I am having an issue with this unit. The hot water pressure coming directly out of the unit is very low. The cold water pressure coming into the unit is more than adequate. I checked then inlet screen filter, looked clean. The unit also shut off twice with an #12 error code. The gas pressure is good, incoming cold water pressure good, venting right through the wall so that's not an issue.

    I will be calling Rinnai tomorrow but wanted to see if anyone else has had the same issue.

    Thanks in advance for your replies.

  2. #2
    DIY Senior Member zl700's Avatar
    Join Date
    Aug 2009


    Describe "good gas pressure"
    What is the static pressure when off, full fire, and full fire with other appliances on, measured in inches of water column??

    You bought their smallest unit, look at the performance charts to determine gpm at a given temp rise, it may be all the heater can do.
    Last edited by zl700; 04-10-2010 at 02:59 PM.

  3. #3


    Agree, If you are getting #12 codes my guess is that good gas pressure ain't so good. You need between 6-10"ng or 8-13.5LP with a 1" pressure drop or less when running (Dynamic pressure).

    In PA I'd expect the R50 to do a one bath home with a standard shower but not much more. You are looking at about 3-4gpm (ish) from this unit.

  4. #4
    Retired prof. engr. gator37's Avatar
    Join Date
    Nov 2009


    You might want to review the manuf. lit., if I remember right those units have a large water pressure drop associated with them.

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