water volume question

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by monkeybrains, Nov 11, 2010.

  1. monkeybrains

    monkeybrains New Member

    Messages:
    7
    Location:
    new york
    I am trying to increase the water volume to my house. I currently have a 5/8 water meter to a 3/4 main that runs about 30 feet to the prv which ive replaced with a watts 223 and then goes to rinnai instant heaters. I cannot upsize the main or meter due to ridiculous charges by our local municipalities. H2O pressure from the street is 125 psi. Do you think I could increase flow by increasing to 1 inch as the main enters the house upstream of the prv, then going with a watts 223 1 inch prv and 1 inch pipe to the rinnais, theen i could plumb 1 inch pipes to the risers going upstairs. I am currently only able to get about 7 gpm out of our master shower and I plumbed 3/4 all the way to the drop ear elbows through a hansgrohe volume control and 3/4 thermo mixer, it just seems like we should be getting much more water flow. Also we got about 10gpm before the rinnais were installed and just had a 50 gal h2o water heater.
  2. Cookie

    Cookie .

    Messages:
    5,660
    Location:
    .
    Instead of replacing all that piping see if you can find a PRV that will allow you to adjust the pressure up higher than what you have now, this will give you a faster flow which will equate to more gpm, but, I am not sure if they make PRV's that are adjustable to a 100 PSI. Or for that matter, remove the PRV, the only real concern would be if you had a water softener because the tanks are only rated for 125 PSI. Removing the PRV may go against your local codes, and is not really a good idea but is a way to boost the GPM.
  3. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    80 Psi is the max...
  4. Thatguy

    Thatguy Homeowner

    Messages:
    1,460
    Location:
    MD
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,486
    Location:
    Cave Creek, Arizona
    If you had good flow before installing the Rinnai and poor flow afterwards, then the problem seems to be the flow regulator IN the Rinnai, NOT your supply lines. If that is the case, then the shower valve would automatically reduce the cold volume/pressure to match the hot. Heaters are rated for 150 psi and the standard relief valves release at that pressure. From your description we cannot tell what you would have to do to increase the general volume of the system because the restriction could be anywhere between the city main and the faucets. Most PRVs can be adjusted to higher pressures which would help the rest of the system, but NOT the hot water if the problem is indeed in the Rinnai heater.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,892
    Location:
    New England
    One way some tankless systems try to ensure they can meet their delta T (temperature rise) figures is to have a flow restriction in them. Don't know if yours does, but it is likely the cause of your reduced flow. Some of them can be cascaded (i.e., installed in series) and then the flow restriction probably can be eliminated.

    A larger main line and meter in many places means a greater 'demand' charge (the ability to draw more water, even if you don't use it, you could). So, what you were seeing is fairly common. Now, whether it is ridiculous or not, if you think about what you are demanding of the system, it means the whole supply system needs to be able to meet your demand - pumps, pipe sizes, supply, etc., without impacting any other customers.
  7. monkeybrains

    monkeybrains New Member

    Messages:
    7
    Location:
    new york
    the city wants $40000 to install a 3/4" meter and they wont allow a 1" main to be hooked to a 5/8" meter. I have 3 rinnais in parallel and with our ground water temp they should each make 4.5 - 5 gpm at 120 degrees. If I take the plumbing downstream of the rinnais out of the loop (hook up hoses to the rinnais and run them out to the street) then I can get the rated flows, but when I run the rinnais through the plumbing to the fixtures I cant get more than about 6 - 7 gpm, I definitely get more flow through the cold side. I know that the rinnais restrict flow but it seems like I should be able to get more flow to our shower.
    Last edited: Nov 12, 2010
  8. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    I hope you mean the tankless are in PARALLEL, not SERIES> Series connection would add quite a lot of resistance, and would still only give you 5 gpm of hot water.
  9. monkeybrains

    monkeybrains New Member

    Messages:
    7
    Location:
    new york
    Yes they are plumbed in parallel, sorry. The prv is currently wide open. I changed the prv to the watts 223 because it was supposed to increase flow nut I didn't notice any significant change. Also when they installed the rinnais they moved them to the far end of the basement which added about 60 feet of pipe and a bunch of elbows.
    Last edited: Nov 12, 2010
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