New water heater still leaking from pressure relief valve

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by kb, Feb 8, 2005.

  1. kb

    kb New Member

    Messages:
    4
    I have a 10 year old house that had 6 year 50 gallon gas water heater. Everything was fine up to this past fall when the pressure relief valve started leaking about 1/2 gallon of water a week, changing the pressure relief valve didn't help. Last week the water heater finally gave up the ghost, it was leaking from the top. I replaced the water heater myself with another 50 gallon gas model (12 year) the pressure relief valve is leaking just as much water as the old water heater. I put a pressure gauge on the hose bib and average 80 psi during the day. My question is, what would of changed in my plumbing system over the years to cause the pressure relief valve to start leaking? Do I need an expansion tank or maybe reduce the pressure? Thanks! Keith

    Great forum btw! :)
  2. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,623
    Location:
    Cave Creek, Arizona
    hj

    If it is an expansion problem which is likely, you cannot go by the "average". You have to watch the gauge while the water heater is operating, because that is when the pressure will rise, and it will drop immediately as soon as any water is used in the house.
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    80 is a little high, actually right at the maximum recommended pressure. From that point, it may very well be an expansion problem. Try to observe the pressure gauge during a period when lots of hot is used and then the burner runs for a while to make up. If it is geting up over 120 , you are in the region where a TP could drip.
  4. kb

    kb New Member

    Messages:
    4
    Thanks for the replys, I checked the pressure this morning after my teenage kids took longggggg showers :eek: intitaly the pressure was slighty over 120 psi, now down to 100 psi as I type this. Can I reduce the pressure at the meter where the water comes into the house by just turning down the shut off valve? or do I need to install pressure regulator in-line? :confused:

    just checked before I hit reply, now back to slighlty over 120 psi :(
  5. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,623
    Location:
    Cave Creek, Arizona
    pressure

    Turn down the valve only affects the volume, the pressure will stay the same. Installing a PRV will do nothing to reduce expansion pressure which is being generated inside the house, after the proposed location for the PRV. An expansion tank is the only solution to controlling the pressure buildup.
  6. kb

    kb New Member

    Messages:
    4
    Ok, I'm going to install a 5 gallon expansion tank, but do I need to install a PRV too?
  7. ally68

    ally68 New Member

    Messages:
    67
    Location:
    Missouri
    I would because at 80-90 psi incoming pressure your expansion tank will only absorb up to 150 then your valve will leak again mine was like yours I installed a PRV got my incoming pressure down to 50 psi now it only goes up to 80 or 85 when heater runs so i did not install an expansion tank and had no problems. Plus if the main pressure goes up at night like so many of them do you could easly have well over 100 psi from your main and it may fill your expansion tank quickly.
  8. kb

    kb New Member

    Messages:
    4
    Thanks for the reply, does it matter where I locate the PRV? should it be just past the water meter or closer to the water heater?
  9. ally68

    ally68 New Member

    Messages:
    67
    Location:
    Missouri
    mine is right off the main just after it enters my house but all my plumbing is in the basement.
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