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Thread: lose of hot water pressure cold is fine

  1. #1

    Default lose of hot water pressure cold is fine

    Hey all and thanks for taking the time to read this post. First off the whole house has a loss of hot water pressure. Running all the hot water at once usually means a few faucets or tubs are dripping. This started about 2 weeks ago with a slight reduction of pressure and heat. I have drained the hot water tank. Capacity on placard states 58 gals. I got about 45 gals and it took about 40 mins to drain it . I thought this was an excessive amount of time. I turned the pump off and closed the incoming water line also opened the pressure poppet to drain the tank. Refilled the tank. While filling the tank I watched the pressure gauge. Pump came on @ about 42 psi. and kicked out at 60psi. I then cut off the pump and allowed the system to deplete. Checked the air charge on the holding tank it was 30 psi. To me it seems like there is a blockage somewhere in the hot water heater. This has happened once before and the tank was replaced all was fine at that point. I saw on another post by doing a search someone had suggested trying to blow the blockage back to the tank by stopping up a faucet/shower head and turning the hot and cold water on. Drain the tank before hand so the cold can back flush the hot water lines. I am open for sugeestions and am I on the right track here.
    Last edited by ooootis; 02-11-2006 at 01:27 PM.

  2. #2
    DIY Senior Member Mike Swearingen's Avatar
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    When draining a water heater, open a few hot water taps for air, in addition to the T&P valve. It should drain much faster. (Turn off the power to it first, of course.)
    If your pump is set at 40-60 psi cut-on/cut-off, the pressure tank should be two psi below the cut-on, or at 38 psi. With the pump off and the water pressure all drained off, check the tank again with a tire pressure gauge. Your's should be 38 psi. If it needs air, then air it up to that with a bicycle pump or portable air tank or compressor.
    Usually, hot water pressure should be about equal to the cold water pressure going into the tank. Make certain that the cold water supply valve to it is wide open. If it seems to be, and the hot water pressure is still too low, I would turn off the pump and take that valve apart to check it and clean any build-up or debris from it first.
    If that valve is O.K., then there may be water heater debris clogging the hot water side of the various facuets, and you may have to take each apart to clear it.
    Good Luck!
    Mike

  3. #3

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    Thanks for the help Mike. Once the water is hot I'm going to herd everyone to the showers then start back at it. I will adjust the tank pressure to 38 psi

  4. #4
    DIY Senior Member Mike Swearingen's Avatar
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    Another way to check the pressure from the water heater is to get an inexpensive water pressure gauge that screws onto any water hose outlet, such as the drain of the water heater. If the pressure from the water heater doesn't match the pressure at an outside spigot, then the problem is probably in the cold water supply valve to the heater.
    Good luck!
    Mike

  5. #5

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    I went down and looked at the cold water 1/4 turn valve and disassembly for inspection or cleaning will require it to be sweated out and of course back in.

    I doubt the 1/4 turn valve because I turned the water on with the garden hose hooked up to the heater drain and it did appear to better than any of the fixtures in the house. Of course I will not discount the flow gauge test. Where can I purchase that tool on Sunday? Lowes or Home Depot.

  6. #6
    Plumber plumber1's Avatar
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    I doubt we're talking about pressure.
    You probably have a restriction somewhere and you really mean volume.

  7. #7

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    Yeah I recon volume is a better description doesn't change anything in the big picture no water is no water

  8. #8
    Plumber plumber1's Avatar
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    From where I sit, I'd look for a restriction on the hot water outlet of the water heater.
    If there is union right there disconnect and push a steel rod or something like that down into the tank.
    See what you find....

  9. #9

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    Thanks folks. Tank was complete soldered in sooooo did everthing everyone said less a flow meter and came to the conclusion the tank was plugged (again I even have a softner and double house filters) somehow. Replaced it with a space age smart heater and voila hot water and no lack of volume from the hot side.

    thanks
    Dave

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