vacuum relief valve?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by KKfromNJ, Sep 5, 2008.

  1. KKfromNJ

    KKfromNJ New Member

    Messages:
    15
    Location:
    NJ
    I live in New Jersey and am replacing a 10 year old gas water heater; the instructions (Kenmore) mention a expansion tank or a vacuum relief valve. We have neither now, do I need one, is it required?

    Thanks
    KK
  2. patrick88

    patrick88 Plumber

    Messages:
    836
    Location:
    Webster Ma.
    If the installation instructions tell you one is needed then you need it. If you don't have one they may not honor any implied warranty.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,810
    Location:
    New England
    You may or may not need an expansion tank. Water expands when it is heated. It can exert signficant pressure - enough to damage a water heater if it has nowhere to go. Many homes have what is referred to as a closed water system - it comes in, but is prevented from back-flowing back to the supply. This can be caused by a check-valve or a PRV. If you have either of those, then you should have an expansion tank. If you don't have a closed system, the expanded water goes back out to the main.

    A vacuum relief valve would prevent damage if the wrong set of circumstances existed to the tank.

    One other thing that is required in some places is a tempering valve to restrict the outlet water temperature should the WH thermostat fail, or you wanted to extend its capactity by storing hotter water than is typically safe. By having hotter water stored in the tank, you can mix more cold in, depleting the tank slower. You'll lose more energy because the bigger the differential between the tank and the room is larger, but not to heat it since you are using less.
  4. KKfromNJ

    KKfromNJ New Member

    Messages:
    15
    Location:
    NJ
    Thanks for the help; I appreciate everyone’s time. I just took a look, the tank has a pressure relief valve (PRV ?) and there isn’t any other valve between the tank and the house supply. The instructions say install a expansion tank if you have a closed system and the vacuum relief valve says "according to local codes".

    Thanks
    KK
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,810
    Location:
    New England
    Not quite...the safety valve on the WH is a T&P (temperature and pressure) relief valve. A PRV is a pressure-reduction valve which is usually located close to the water inlet of the house - near the shutoff and water meter.

    A vacuum breaker can be useful anywhere, and is required in some areas.
  6. KKfromNJ

    KKfromNJ New Member

    Messages:
    15
    Location:
    NJ
    We only have the meter and then the shutoff. I’m going to install a vacuum relief valve.

    Thanks
  7. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Since this is a gas water heater, did you call the gas utility first? They don't look kindly on folks messing with gas piping without permits and inspections. You should also give a call to the local plumbing or mechanical inspector to verify the venting is proper.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,810
    Location:
    New England
    Some meters have a built-in check valve...you need to check with the utility or your inspector. If it does, that makes it a closed system, necessitating the expansion tank.
  9. KKfromNJ

    KKfromNJ New Member

    Messages:
    15
    Location:
    NJ
    Funny thing about the gas company, glad you brought it up. I’m replacing this for my parents who had a “service contract†with PSE&G. My Dad called them first, of course water heater replacement was NOT covered in the contract, worthless. The PSE&G guy told me I’d be better off having someone else replace it because PSE&G really charged a lot, at least $900. I said I was pretty handy, built my parents rear addition, did the electrical, hot water baseboard (not the boiler) etc. He suggested it was piece of cake, easy. Said if I had any doubts when I was done, call them they would check it out. I found that strange. Last time I saw our plumbing inspector, he was so drunk he could barely make it down the basement stairs.

    I’ll try and find out about the water meter, but it is about 20-30 years old, this will be our 4th water heater and we’ve never had a expansion tank on the water line. I’ll have to see if I can find out.

    Thanks Again
    KK
  10. nhmaster

    nhmaster Master Plumber

    Messages:
    3,189
    Location:
    S. Maine
    Well then, best of luck to you.

    Just remember though GAS GOES BOOM
  11. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,302
    Location:
    Yakima WA
    Kk from NJ, check your private messages.:)
    Last edited: Sep 5, 2008
  12. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,258
    Location:
    Cave Creek, Arizona
    valve

    Some places use PRV to indicate a pressure relief valven and use the term interchangealby with termperature and pressure relief valve. A vacuum relief valve is only necessary if the water heater is in one of the upper levels of the house or in the attic.
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