complete supply overhaul, flow is too low everywhere

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by kirkwood, Oct 9, 2004.

  1. kirkwood

    kirkwood New Member

    Messages:
    2
    Hi, nice board you have here, been reading and now have a problem of my own.

    We had to replace all of our supply lines as they were the old galvanized iron type, leaky and full of gunk - they'd been merged with copper without dielectric unions some time ago.

    We installed 3/4 copper throughout as our house is small and single story, only reducing to 1/2 at each threaded male fixture nipple. We also installed a tankless, electric water heater with a max output of 3gpm.
    On a whim we put a pressure guage in just before the cold input to the water heater.
    After flushing the new lines we pressurized and worked the air out out.
    Everything functioned correctly but the gauge showed 88psi ! So we installed a pressure regulator and another gauge immediately behind it ( which now reads 53psi statically ) and then a pair of filters. The origianl gauge, about 25-30 feet downstream, now reads 49 statically.
    Here are the problems (2):
    (1) flow is really low at any given fixture and opening 2 at once really cuts it, any combo of cold and hot. its as if the pipes allow
    (2) the hot water heater can only supply 3gpm max, demand too much and it only reaches luke warm.
    This is easily done so one has to learn how much to open each fixture ( will we have to train our guests? ).
    Too little, less than .25gpm or 5psi and it will cut off, too much and it will not heat adequately ( this thing draws 99 AMPs when firing full bore ).
    Turning on the cold somewhere while asking for hot effectively cuts the heaters cold supply enough to shut it down or seriously degrade its output.

    Seems like we didn't balance things properly and are unsure how best to proceed,
    all fixtures perform similarly, so debris is probably not the problem. Showering is very unsatisfactory as there is little pressure even through 5 feet of 1/2 pipe to the showerhead.
    Residual pressure from flushing the nearby toilet drops from 49 to 12psi at the guage which is about 20 feet from the toilet.

    Should we replace the runs to the last fixtures with 1/2 as you mention in several places here?
    Should we redo a large portion of it with 1/2 as it is a small area?
    Should we put a 3 gpm flow restrictor immediately after the hot water output?
    any insight appreciated.
    thanks in advance
  2. LonnythePlumber

    LonnythePlumber Plumber, Contractor, Attorney

    Messages:
    319
    Location:
    Wichita, Kansas
    Water Service

    You may have pressure but you dont' have volume. Have you had your water service replaced? I won't think 88 psi would need a pressure reducing valve but others have a stricter standard.
    In buying a heater that will only supply two fixtures, think of all the money you will save by not having hot water :rolleyes: . Oops, I see you're electric. Maybe you won't get to save any money over a gas tank heater :cool: .
    My sarcasm must mean I have not changed over to the tankless heater concept yet. They do require some life style changes.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,797
    Location:
    Cave Creek, Arizona
    heater

    Maybe you are doing better than average. I saw a quote from a manufacturer in a trade magazine yesterday that said, "A 240 volt heater with three 50 amp breakers, (that's 150 amps, folks), will not provide hot water for two showers at the same time. And if you are only getting a 5 psi drop through the heater, probably because you only start with a relatively low initial pressure that is also doing good, because the ones I have seen cause up to a 25 psi drop in the hot water side, and that can create havoc if the shower valve is not pressure balanced and others start opening faucets or flushing toilets.
  4. kirkwood

    kirkwood New Member

    Messages:
    2
    found the problem....

    The filters I used were too dense, removing them corrected the flow issues. now we'll see how it is to live with that water heater when it doesn't overheat due to lack of flow....
    I'm pretty sure I'll have to install and tune a valve on the hot demand to keep things under control, under 3gpm no matter what.
    Thanks for your inputs, I really appreciate you.
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,797
    Location:
    Cave Creek, Arizona
    water heater

    It will not overheat due to lack of flow, it should just heat less until the flow increases.
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