Hot water pressure problem

Discussion in 'General Plumbing Help' started by Matt1984, Sep 14, 2019 at 6:35 AM.

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  1. Sep 14, 2019 at 6:35 AM #1

    Matt1984

    Matt1984

    Matt1984

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    Hi there,

    We have a house without a backflow preventer on the main, a water softener, a whole house carbon filter, and a hot water tank with a check valve on the cold water inlet. The softener and filter are installed upstream of any toilets, appliances, taps, or the heater.

    During times when there’s a high demand for cold water (usually a combination of washing machine/dishwasher running, and toilets flushing), it seems like the system is trying to pull the additional cold water from the hot water tank. The check valve gets pulled up and gets stuck. Cold water can come in and fill the tank, but it’s at a slower flow rate than typical. When we first turn on the hot water under these conditions, the pressure is fine for a few seconds, and then tapers down into a lower pressure. The cold water pressure is unaffected.

    We can usually fix this (reset the check valve) once the heater is refilled, not running water anywhere else in the house (to maximize pressure), and turning on a hot water tap full blast. Sometimes it takes a few tries. In one or two bad instances, I’ve had to take off the inlet pipe and loosen the check valve manually.

    Is there anything we can do to stop this? It seems to be getting worse and I replace the carbon filters often.

    We need the water softener and carbon filter as the town uses a lot of chlorine to clean/disinfect the water, and it tastes and smells bad without the filter (and is likely bad for the appliances).

    I was thinking of adding an expansion tank but I don’t know if it would do anything (perhaps it would if we didn’t have the check valve on the heater but we do and it’s a rental, and while I’d like to swap it out for our own, finances aren’t great right now, and I’d prefer to wait a few months once we start pulling in some more money).

    Thanks in advance, Matt.
     
  2. Sep 14, 2019 at 10:27 AM #2

    Jeff Handy

    Jeff Handy

    Jeff Handy

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    Is the water heater “check valve” just a heat trap nipple with a captive ball?

    If so, why not just replace it with a regular nipple?

    You are wasting hot water now anyway, having to blast it to try to unstick that valve?
     
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  3. Sep 14, 2019 at 10:29 AM #3

    Jeff Handy

    Jeff Handy

    Jeff Handy

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    Meanwhile, if you are renting, your landlord should fix and pay for repairs.
     
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  4. Sep 14, 2019 at 12:04 PM #4

    Matt1984

    Matt1984

    Matt1984

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    Thanks Jeff!

    Sorry or the confusion, we own the house, but we rent the water heater from the gas company.

    Also, regarding your definition of the check valve, it sounds like you’re describing what we have. It basically looks like a Sorry board game piece, or a thin, plastic pawn (♟) inside a small chamber. It’s housed within a coupling that is sunken into the top, inlet section of the tank.

    It does look like it can be swapped/removed though, but I’ll call the renting company first just to make sure it can be removed and won’t damage the unit, or to see if they would need to remove it.

    If I do remove it, would there be any benefit to putting an expansion tank on the inlet of the tank?
     
  5. Sep 14, 2019 at 12:15 PM #5

    Jeff Handy

    Jeff Handy

    Jeff Handy

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    You can ask the pros here about the expansion tank.
    I think it would go on the hot side, but wait for them to weigh in.

    If you replace the heat trap nipple, make sure you install a dielectric nipple or dielectric union, you can find info on that on Google.

    All it does is use plastic linings or spacers to prevent slight electrical charges from flowing through the metal parts at that connection, which can eat away at the metal over time.
     
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  6. Sep 14, 2019 at 12:18 PM #6

    Jeff Handy

    Jeff Handy

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    And with that heat trap fitting gone, you should pbly get better flow rate due to the full pipe being open bore, no little plastic piece inside choking it back.
     
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  7. Sep 14, 2019 at 12:31 PM #7

    Jeff Handy

    Jeff Handy

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    Some people don’t like dielectric unions or nipples, they feel they actually are a weak link, but I think they are code required.

    Sometimes using a long brass nipple is preferred if allowed, as a transition coupling.
     
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  8. Sep 14, 2019 at 1:12 PM #8

    Matt1984

    Matt1984

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    Thanks again Jeff! I appreciate the help/insight!
     
  9. Sep 14, 2019 at 10:07 PM #9

    Diehard

    Diehard

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    You should understand that heat trap nipples do not prevent backflow if working properly. They are thermal convection preventers to stop the heat from rising and cold water from sinking in the absence of flow.
    When the water heater was installed it would have had an expansion tank installed with it(typically on the cold water side) if there was any device that prevented the cold water from expanding back into the main water service.
    I have no experience with heat trap nipples but as mentioned they would inherently restrict the flow somewhat I would think and I would think subject to blockage and perhaps even the ball sticking.
    If I had a a water softener and whole house carbon filter, I would definitely be looking at my upstream and downstream pressures under flow.

    Of course it not easy to connect a pressure gauge, except at hose bib outlets, to test where pressure is being lost while flowing. But that would be the best way to tie it down.
     
  10. Sep 14, 2019 at 10:40 PM #10

    Jeff Handy

    Jeff Handy

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    You should be able to temporarily screw on a hose threaded pressure gauge to the drain hose bib of your water heater, if that would give you any insight into pressure loss.

    I would flush the water heater first, by attaching a short garden hose to that drain fitting, and rapidly running at least ten or twenty gallons of water out, into a floor drain or sump pit or whatever.

    If not flushed, the heater sediment could clog up the pressure gauge, I think.
     

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