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  1. #1
    Join Date
    Jul 2011
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    Default Low hot water pressure, cold is good

    I have a 1999 gas hot water heater. Copper pipes in and out of the nipples. Water pressure was 50psi on my drain gauge as it came out. The anode was replaced with a new one. Wire was pretty bare. There were some mineral deposits still caked on, but I'm wondering if those are blocking the hot water exit. Aerators were taken off and cleaned.Changed vacuum relief valve because it was pooling water above the spring. Cold water nipple was clear. Should I cut the copper above the h/w nipple and see if there is blockage? Tried process of elimination. Drained h/w heater completely.
    Last edited by Briguyz; 07-02-2011 at 01:01 PM. Reason: forgot a line

  2. #2
    Join Date
    Jul 2010
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    Default Re: Low hot water pressure, cold is good

    Yes, go ahead and cut the hot copper. Use a tube cutter to get a good cut. Remove the nipple and examine it. If plugged, replace it, use a coupling to reconnect where you cut the pipe. Fill the w/h and see if you have good pressure.

    If your w/h was installed in 1999, it maybe time for a new unit.

    When you drained the w/h, was the water coming out fast or slow?

    Please report back your findings.

  3. #3
    Join Date
    Jul 2011
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    Default Re: Low hot water pressure, cold is good

    Gauge said 50 psi, but it seemed pretty good pressure . It wasn't dribbling, it was steady. Emptied 40 gallons, all clear water

  4. #4
    Join Date
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    Default Re: Low hot water pressure, cold is good

    Quote Originally Posted by Briguyz View Post
    I have a 1999 gas hot water heater. Copper pipes in and out of the nipples. Water pressure was 50psi on my drain gauge as it came out. The anode was replaced with a new one. Wire was pretty bare. There were some mineral deposits still caked on, but I'm wondering if those are blocking the hot water exit. Aerators were taken off and cleaned.Changed vacuum relief valve because it was pooling water above the spring. Cold water nipple was clear. Should I cut the copper above the h/w nipple and see if there is blockage? Tried process of elimination. Drained h/w heater completely.
    Quote Originally Posted by Briguyz View Post
    Gauge said 50 psi, but it seemed pretty good pressure . It wasn't dribbling, it was steady. Emptied 40 gallons, all clear water
    Hot water supply is pretty simple and straight forward --- open a hot water faucet to allow flow --- cold water enters the tank at the same time replacing the same volume being drawn out --- for the most part , hot water pressure out is about the same as the pressure of the incoming cold water supply to the tank.

    Now , you may be experiencing a low flow condition which means there is a restricion somewhere. Is there a check valve on either the hot or cold water nipples? It may be sticking.
    Perhaps the discharge dip tube may be plugged -- remove the hot water nipple and check.

    If I read your posts correctly -- you placed a pressure gauge on the drain? If so I don't see any advantge of doing so. You have a water column of 3 - 4 feet and with -- say -- 40 gallons of water along with gravity will provide the pressure you saw --- which dosen't prove anything.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  5. #5
    Join Date
    Jul 2011
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    4

    Default Re: Low hot water pressure, cold is good

    I understand about the gravity and pressures, but I was curious about the psi anyway. I just tried to get as much information as I could. I had the gauge so I said why not, before I started cutting pipe. Thank you for your reply . Checking the hot nipple is my next step.

  6. #6
    Join Date
    Jul 2011
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    4

    Default Re: Low hot water pressure, cold is good

    UPDATE: Cut the copper hot "out" pipe, twisted off hot nipple . There was hard, crusted sediment down inside. Used screwdriver to chip away and it did the trick. That was the blockage of low hot pressure throughout the house. Reassembled and regained full hot water pressure. Yay!

  7. #7
    Join Date
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    Default Re: Low hot water pressure, cold is good

    Good stuff and thanks for posting back with the result.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  8. #8
    Join Date
    May 2008
    Location
    Pacific Northwet
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    1,359

    Default Re: Low hot water pressure, cold is good

    It's good to hear you got it fixed. For everyone else reading this...

    Just a note on the pressure gauge: the pressure you note is only relevant while water is flowing. With no flow, your pipe could be nearly blocked and it will show about the same pressure as anywhere else in the line. (Elevation matters -- every 2.31 feet of rise results in 1 PSI of static pressure drop.)

    With the gauge attached to the drain on the water heater, open a bathtub hot water tap full flow. If the blockage is on the cold water side of the water heater, you should see a noticeable drop in pressure. If the blockage is on the hot water side, you will see little drop in pressure.

    Note that most sink faucets, even with the aerators removed, will limit the flow of water -- the hole in the valve might be smaller than the hole through the blockage in the pipe, so opening a sink faucet may not prove anything.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

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