Water heater TPR valve issue

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by rockpile7, Apr 12, 2010.

  1. rockpile7

    rockpile7 New Member

    Messages:
    19
    Location:
    NJ
    I have a 5 yr old Rheem Guardian 50 gallon water heater. All of a sudden, my TPR valve is opening and draining about a quart of water at almost exact intervals of 10 minutes apart. My town notified me they would be doing some flushing/testing of fire hydrants. Can anyone confirm whether this would be the cause, and what should I do. I turned off the water heater already.

    Thanks in advance for your responses.

    John
  2. Terry

    Terry Administrator Staff Member

    Messages:
    15,005
    Location:
    Bothell, Washington
    Flushing hydrants isn't going to affect your water heater.

    It's five years old though.
    Take a pressure gage and find out what kind of pressure you have.
    If the pressure is over 80 PSI, you will need to reduce pressure and add an expansion tank.
    If the home has been under high pressure for years, you may need a new T&P also.
  3. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,641
    Location:
    Cave Creek, Arizona
    IF you have a bad pressure reducing valve it could take 10 minutes to leak enough to overpressurize the system and open the relief valve. When it opened, it would reduce the pressure to normal, and then the process would repeat itself, and repeat it self, etc. This assumes your city's pressure is above the T&P valves setting. Without knowing what the your normal pressure is, what it is when the valve discharges, and WHY it changes between the two times, if it does, we cannot diagnose it from here. Changing the T&P valve without knowing why it is discharging, however, might be a waste of time and money.
  4. rockpile7

    rockpile7 New Member

    Messages:
    19
    Location:
    NJ
    Thanks guys.

    The curious thing is, I called the water company today and they confirmed they were flushing/testing hydrants in my area last night. Since about 2:00 am I have not had the problem again. It is really strange. I can only assume they did something to increase the pressure, but they told me no. My next step will be to test the water pressure as Terry recommends.

    Thanks for your help
    John
  5. Terry

    Terry Administrator Staff Member

    Messages:
    15,005
    Location:
    Bothell, Washington
    Testing a hydrant means they open it up to make sure it isn't broken or stuck.
    It also helps flush out stale water that would have nowhere to go if the hydrant was never used.

    If anything, open more faucets will lower pressure.
    Pressure rises during the night, when people are sleeping, and nobody is using water.
    That's why some leaks only occur in the late evening and early morning hours.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,641
    Location:
    Cave Creek, Arizona
    You can get pressure "spikes" if there is a fire in the area, because the pumper trucks will pull a huge volume reducing the pressure in the main, and then when the hoses are shut off, the water velocity causes the equivalent of a water hammer increasing the pressure for a short time. The only way flushing hydrants could cause that same effect would be if they could close them rapidly from a fully open condition.
  7. Terry

    Terry Administrator Staff Member

    Messages:
    15,005
    Location:
    Bothell, Washington
    And my brother-in -law that worked at the city utility said if you shut them off that quckly, it could break the 8" mains.
  8. rockpile7

    rockpile7 New Member

    Messages:
    19
    Location:
    NJ
    Thanks again guys!
  9. FloridaOrange

    FloridaOrange Plumbing Designer

    Messages:
    1,317
    Location:
    SW Florida
    Not saying this is necessarily the case here but may be relevant to the conversation. We've had mains served by multiple pumps at the utility station and to get an accurate reading for a fire flow test we had to have the utility turn on more pumps than what typically runs during that part of the year. These pumps are typically ramped up as needed (during season) and in coordination with the fire department during off seasons, when we first got our original flow test for a project the numbers were so far off that any building 2 stories or more would need a fire pump. Once we had the utilities coordinate with the dept. doing the flow test our numbers were fine. What I'm basically throwing out there is the utility could have been throttling pumps.
  10. rockpile7

    rockpile7 New Member

    Messages:
    19
    Location:
    NJ
    Matt, Terry and others,

    Thanks for all your input. I just wnet out and got a water pressure testing gauge. My water pressure is 125 psi. I was shocked it was so high. I am going to put in a new PRV myself, within the next couple days. It looks fairly straightforward to replace, I have some DIY plumbing experience (change water lines, put in new water heaters....). I would add a picture of my current pressure reducing valve, but I don't have a digital camera. My cell phone picture stinks as well. When my son gets home, I'll ask him to take a picture of my existing set-up.

    To make a long story short, is there a good PRV valve you guys can recommend. It is 3/4". I've looked at the Watts, but cant determine the model I would need. I know I'm probably not giving enough info, but if you can lead me the right way before I go to the plumbing supply, that would be great.

    thanks
    John
  11. Terry

    Terry Administrator Staff Member

    Messages:
    15,005
    Location:
    Bothell, Washington
    Most of the brands will be fine on the PRV,
    It's a pretty simple device.

    You will want to add an expansion tank while you are at it though.
  12. rockpile7

    rockpile7 New Member

    Messages:
    19
    Location:
    NJ
    Thanks Terry, and yes, I will be adding the expansion tank.
    As soon as I can get a picture, I will need advice as to where to put the tank since there may be some space contstraints

    John
  13. ilya

    ilya In the Trades

    Messages:
    105
    Location:
    Akron Ohio
    the pumper trucks will pull a huge volume reducing the pressure in the main,

    Several years ago we had a huge multi-alarm fire at the local country club. The pumpers pulled so much water that homes nearby not only had no water, they got a sucking noise through their open taps. I just checked pressure in a duplex today. Unit A: 155 psi. Unit B: 60 psi. Landlady had prv's installed 5 yrs. ago. Seems they should last longer than that.
    Last edited: Apr 14, 2010
  14. Redwood

    Redwood Master Plumber

    Messages:
    7,450
    Location:
    Connecticut
  15. rockpile7

    rockpile7 New Member

    Messages:
    19
    Location:
    NJ
    Thanks Redwood,
    I took your advise and picked up the 25AUB-Z3. I just have a stupid question before I replace it. The PRV I currently have is a Wilkins, but it's the same basic design as the Watts. On the inlet side, it looks like the brass female connection is attached to the valve body with a collet/nut (whichever is the correct term). Am i right in assuming this should not be loosened or touched at all?
    My plan is to cut the pipe on the outlet side and unscrew the existing valve. I sweat a new 3/4 male adapter to a new piece of pipe. I screw on the new valve at the inlet side. I sweat a coupling to connect the pipes on the outlet side. Am I missing anything or is that all there is to it.
    My only concern is, it will probably be difficult to tighten the valve on the inlet side to get it exactly aligned as it is now.

    Thanks
    John
  16. Redwood

    Redwood Master Plumber

    Messages:
    7,450
    Location:
    Connecticut
    The nut you speak of on the inlet of the 25AUB-Z3 is a union to make installing easy.
    Do unscrew it so you can thread the PRV on one male adapter and then the nut and union screws on the male adapter on the inlet.
    Finally connect the union using a dab of grease to keep the o-ring in place.
  17. rockpile7

    rockpile7 New Member

    Messages:
    19
    Location:
    NJ
    Thanks Redwood,

    I actually started a new post with my prior question regarding the PRV since it was a new topic. Now, however, you've answered my question.

    thanks again, I'll let you know how it goes.

    John
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