T&P discharged last night

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by firefly, Aug 15, 2008.

  1. firefly

    firefly Junior Member

    Messages:
    10
    Location:
    long island
    My Vaughn indirect water heater decided to relieve itself last night in my basement. My $10 floor mounted leak alarm saved the day, but by then there was 5 shop vacs worth of water on the floor. It didnt just blow-off and stop. I found it gushing continually at full force. I had to shut off the city water inlet valve. Why would this happen? System is only 5 years old.
    Last edited: Aug 15, 2008
  2. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    only 4 things will cause the T&P to discharge, and this is not in any specific order...

    #1 a water temp to high...around 200F... you would probably know if this was the problem as the water would be coming out of the faucets scalding.

    #2 pressure at or above 150#s...this you can check with a pressure gauge that has a high limit of 200#s

    #3 the working mechanism inside the T&P failing and causing it to not work properly...if the water is not scalding and the pressure is in the acceptable range then this would likely be the cause.

    #4 a failed expansion tank if you have one...
    Last edited: Aug 15, 2008
  3. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    When checking the pressure you should get a reading of less than 80 PSI.
    I would recommend getting a gauge with a lazy hand (a second needle that records the highest pressure reached) and read over a 24 hour period. Frequently water pressures are higher overnight as water suppliers refill storage tanks during the non-use period.
  4. some more advice

    Mr Cass covered about everything....

    my only bit of advice would be to pipe that t+p valve
    to the nearest floor drain or sump pump pit
    usually very simple and very easy to do....
    (if you have a drain)..

    it makes things not seem as bad when all you have to do
    is just fix the problem and not have to sop up the whole
    basement....
  5. firefly

    firefly Junior Member

    Messages:
    10
    Location:
    long island
    #1 a water temp to high...NO - IT WAS NORMAL
    #2 pressure at or above 150#s...SEEMS DOUBTFUL THAT A LARGE MUNICIPAL WATER SYSTEM WOULD SPIKE THAT HIGH
    #3 the working mechanism inside the T&P failing - MUST BE THE CAUSE
    #4 a failed expansion tank if you have one - NO TANK


    I just re-activated the system (re-powered the boiler and re-opened the city water valve). I watched it cycle and the T+P remained closed..not even a drip.
  6. firefly

    firefly Junior Member

    Messages:
    10
    Location:
    long island
    No floor drain. No sump pit. :-(
  7. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    Do you need a tank...do you have a pressure reducing valve and or a check valve installed?
  8. bummer


    a large metal trash can might suffice,

    or consider digging a small 5 gallon bucket sized
    sump hole and installing a sump pump
    for further troubles
  9. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    I don't want to burst your bubble but they can, do, and will run pressures that high. If you already have a Pressure Reducing Valve (PRV) it may have been protecting you all along and has failed. The municipal water supplywill send whatever pressure it wants and it is up to the homeowner to deal with it.

    [​IMG]
  10. firefly

    firefly Junior Member

    Messages:
    10
    Location:
    long island
    A pressure reducing valve or check valve to do what?
  11. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    To regulate the pressure to less than 80 PSI.

    If you have one installed it creates a closed system and a thermal expansion tank must also be installed and be operating correctly to keep thermal expansion from causing the system pressure to rise.
  12. firefly

    firefly Junior Member

    Messages:
    10
    Location:
    long island
    A PRV to knock down potentially high city water spikes? But the city water pressure should only drop during a high usage - such as early in the AM when people irrigate their lawns. I cant understand why it would ever rise above normal. The water authority pumps it out of the aquifer up into towering water tanks. From there it feeds by gravity into the mains. Perhaps you think there are booster pumps to help push it along..and maybe one of those pumps went wild?
  13. firefly

    firefly Junior Member

    Messages:
    10
    Location:
    long island
    The only PRV I have is the one that maintains 15# in the oil fired boiler associated with the Vaughn indirect tank. On a call for heat, a relay pulls in a dedicated pump that circulated hot water thru the indirect tank.
  14. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    It doesn't matter what causes the pressure to be high.
    There are many pumps on the municipal system. How do you think water climbs out of wells and reservoirs into those towers?
    There are some systems here the pressure is so high 2 PRV's are needed in series to control it!

    If it is higher than 80 PSI. you need a PRV.
    Step one is measure your pressure like I said.
  15. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    Out here the municipalities need large ammts. of water due to population growth. Once a system gets to its maximum out put the only way it can supply additional water needed is 1 of 2 ways, increasing the pipe diameter by digging up all the pipe on all the streets or increasing pressure. So they increase pressure to save the tax payers $$$ BUT once it is increased then you need a pressure reducing valve once it gets to your house and many areas also require a check valve and with one or both of those you also need an expansion tank.
  16. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,472
    Location:
    Cave Creek, Arizona
    T&p

    If it runs continuously, especially if it is not "almost steam" water, then it is pressure and if that is the case, it will NEVER stop until pressure diminishes or the water supply is turned off.
  17. GrumpyPlumber

    GrumpyPlumber Licensed Grump

    Messages:
    1,404
    Location:
    Licensed Grump
    Just a thought:

    "It appeared that the homeowner and the man renting the house had been trying to fix the water heater, which may have contributed to the heater being launched across Thunderbird Road and landing near a bus stop, Phoenix Fire Captain Sam Richardson said. "

    http://www.azcentral.com/12news/news/articles/2008/08/14/20080814kpnx-waterheater-CP.html

    You could misinterpret the slightest detail online and create a deadly situation.
    Sorry guys, just thought I'd toss that in for safety sake.
  18. GrumpyPlumber

    GrumpyPlumber Licensed Grump

    Messages:
    1,404
    Location:
    Licensed Grump
    Got a call almost 2 years ago, homeowner tells me he'd been fussing with the indirect water heaters T&P and it wouldn't stop leaking.

    Get there to discover it was the boilers T&P, not the water heater.

    He'd plugged it in his exasperation after hours of trying to adjust things and get it to stop.

    Turns out it was the convection loop inside the indirect backfeeding to the boiler, he'd been running his boiler at house pressure and the 30 psi relief was doing it's job up until he plugged it.

    Lucky man, very lucky man.
  19. Grumpy...plugs are cheap

    I have seen that before....

    water heaters with a galvanized plug screwed down
    tight into the T=P valve....


    its worked fine that way for years.......until the day it dont..........


    I would really like to know what they did to blow up that
    electric water heater.......
  20. toolaholic

    toolaholic General Contractor Carpenter

    Messages:
    874
    Location:
    Marin Co. Ca.
    Firefly Millons of homes have P.R.Valves. You May need one .At least take the advice given on the test. People that don't listen here ,return MANY MANY MANY MANY TIMES :eek:

    [​IMG]
    T&P Valve looking at two sides.
    Last edited by a moderator: Apr 24, 2009
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