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    MichaelN61's Avatar
    MichaelN61 Posts: 1, Reputation: 1
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    #1

    Oct 4, 2013, 07:18 AM
    pressure relief vs pressure reducing valves
    Hi - not sure how this site works :).. I had an electric hot water heater replaced and then learned the water flow (coming through the oil furnace) was low. A plumber temporarily removed a pressure value which was causing the problem. Rather than spending $300 to have him do the work, I want to do it myself. Now realizing I am confused as to whether I need a pressure relief or a pressure reducing valve... any thoughts?
    ma0641's Avatar
    ma0641 Posts: 15,675, Reputation: 1012
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    #2

    Oct 4, 2013, 08:02 AM
    Water does not flow through the TPV valve on the heater, it must be free vented. PRV valve is main pressure regulator for house. If you got a new HW heater, a new TPV should have been installed. Must be vented to the floor drain or outside the house. PRV's are pretty interchangeable and you should be able to do it assuming all sweated fittings are the same. Otherwise you will need to sweat a new fitting .
    speedball1's Avatar
    speedball1 Posts: 29,301, Reputation: 1939
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    #3

    Oct 4, 2013, 09:43 AM
    The PRV valve, (see image) is a safety valve on your heater to prevent overpressure and overheating. A PRV valve(see image) is used to reduce the pressure coming into your house. Does this answer your question? Cheers, Tom
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    ma0641's Avatar
    ma0641 Posts: 15,675, Reputation: 1012
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    #4

    Oct 4, 2013, 01:54 PM
    Quote Originally Posted by speedball1 View Post
    The PRV valve, (see image) is a safety valve on your heater to prevent overpressure and overheating. A PRV valve(see image) is used to reduce the pressure coming into your house. Does this answer your question? Cheers, Tom
    OMG: PRV and PRV or PRV and TPV?
    speedball1's Avatar
    speedball1 Posts: 29,301, Reputation: 1939
    Eternal Plumber
    		  
    #5

    Oct 4, 2013, 06:40 PM
    Good catch Brian! I forget to add a "T" to the TPRV. (Temperature Pressure Reliefe Relief Valve.) I'll stand in a corner for two hours. OK? Tom
    massplumber2008's Avatar
    massplumber2008 Posts: 12,832, Reputation: 1212
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    #6

    Oct 4, 2013, 06:50 PM
    No no, Tom, you were correct here. An "oil furnace" (assume boiler by description) would have a PRV (pressure relief valve) and the whole house would have a PRV (pressure regulating valve). The boiler would NOT have a TPV or a TPRV (usually called a T&P relief valve guys)...

    Anyway, you posted pictures that are close enough that Michael should be able to tell us which valve he is talking about and then we can help!

    Mark
    Mike45plus's Avatar
    Mike45plus Posts: 230, Reputation: 27
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    #7

    Oct 5, 2013, 04:58 AM
    Is it possible that Michael has a boiler with a tankless coil? Some tankless coils need a flow restrictor to reduce the gpm so the water can be sufficiently heated as it travels through the coil, perhaps this is the device he is calling a pressure valve. This type of water heater connected to a tankless coil is sometimes called an aqua booster, and it uses electricity to power a circulating pump...
    massplumber2008's Avatar
    massplumber2008 Posts: 12,832, Reputation: 1212
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    #8

    Oct 5, 2013, 06:23 AM
    Hi Mike... yeah, it certainly could be a tankless coil (with or without booster tank) and could be the Watts P-9 flow restrictor valve he is talking about... could be.

    I'll tell you though, if Michael returns and really wants our help I suggest that he take a picture of this "valve" in question or we really won't be able to help much... only guess like we are doing now and that will not help him in any way! That, or he needs to give us the exact name of the valve... that would work, too!
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