Home hot water system question

Discussion in 'Hangar Talk' started by bugsiegel, Jan 12, 2019.

  1. bugsiegel

    bugsiegel Pre-Flight

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    I have a plumbing question I'm sure someone in here can answer.
    This weekend I had to drain the water in the hot water system. (moving one baseboard around)
    To speed up the refill process I tried lifting the lever on the water pressure regulator.
    Just a few inches beyond the water pressure regulator is a water pressure relief valve.
    When I manually opened the regulator the city pressure trips the relief valve and water dumps.
    To me this seems to work like it should because each part seems to be doing what it is intended to do. Boiler is a Slant Fin about 15 years old. I could create a bypass loop with two valves that isolate the higher pressure off the pressure relief valve momentarily.

    Would a bypass loop be the way to introduce city pressure for quick filling ( two stories with old style large water heaters).
    Is the inline water pressure relief valve absolutely necessary ; would the pressure valve built into the boiler pick up the excess water pressure should the inline regulator fail?

    Hope I've given enough info here and thanks in advance.
     
  2. 3393RP

    3393RP Pattern Altitude

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    In large commercial HVAC installations, it's common practice to build a bypass around piping system devices like meters, strainers, PRVs, and water conditioning equipment. They are useful for allowing maintainance of the bypassed devices without system shutdown and, as you suggested, providing a quicker fill of the system.

    You have made a good observation, and your proposed solution is a standard and desireable feature.
     
    Last edited: Jan 12, 2019
  3. bugsiegel

    bugsiegel Pre-Flight

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    I was thinking that I could also simply put a ball valve half way down the dump pipe and close it off during fill up, but I'm unfamiliar with how the inline pressure valve works and not sure if it would continue to allow water through it, to the system, or when it's activated all the water is deflected down the dump pipe.
     
    Last edited: Jan 13, 2019
  4. Kenny Phillips

    Kenny Phillips Cleared for Takeoff

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    We put a bypass in our old Victorian house to make it easier to fix and move radiators. Heck, I put in a bunch of isolation valves (since I got them for free) as we were rearranging walls at the time. Draining down and filling/bleeding a system with three stories and a basement is a PITA. (We had city water exceeding 100 PSI, no problem filling the third floor radiators.)
     
  5. bugsiegel

    bugsiegel Pre-Flight

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    Was able to speak to a plumber friend today who said to me that the inline relief valve next to the pressure regulator is not needed and that it's an old way to plumb. The needed relief valve is the one that is on the boiler and should not be more than 6 inches off the boiler.
    He went further to say that only after the inline relief valve is eliminated would it be legal to install a ball valve after the current pressure regulator to allow isolation for it and that there should not be any ball valve between any pressure relief and the actual boiler.
    Licensed plumbers pop in here any time. If it maters we are talking NYC plumbing.
     
  6. Lndwarrior

    Lndwarrior Pre-takeoff checklist

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    yep, what he said.
     
  7. Lndwarrior

    Lndwarrior Pre-takeoff checklist

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    Not exactly. The inline relief valve next to the pressure regulator is to protect the boiler and piping system should the pressure regulator fail.

    In some installations this could cause excessive pressure in the system that could damage the boiler, control valves, etc..

    Now whether or not this is likely, is another question. If all components of the heating water system are professional quality then the boiler, valves and fittings should be rated for a minimum of 125 psi minimum when new.

    On larger hot water systems it is quite possible to to have high head pumps that produce 50 psi or more (though I doubt yours is this large). In this case a failed regulator could allow city pressure, which could be as high as 80 psi (depending on location) at the inlet of the pump. Then the added 50 psi of the pump could exceed the pressure rating of the boiler and valves. I have seen such a condition and it can ruin a lot of expensive components.

    I can't know what the city pressure is or what the discharge head of your pump is, but I suspect exceeding the design pressure of your system if the relief valve fails may not necessarily exceed the original design system pressure.

    However, there are two other aspects to consider.

    Over the past 15 years, depending on the chemical treatment program, parts of your system may have begun to corrode or deteriorate. This could mean that some components (like the boiler heat exchanger) might fail at a lower pressure than the original design pressure.

    Secondly, having the PRV at the regulator will make it obvious that the regulator has failed. The relief valve at the regulator should set lower than the relief valve at the boiler.

    When the PRV fails at the regulator the water dumping down the indirect waste fitting will be an obvious tell-tale that the regulator has failed - and a simple fix.

    Without the relief valve at the regulator, a failed reducing valve could go undetected for a long time resulting in unnecessarily high pressures in your system that will likely be just below the boiler PRV relief pressure.

    Over time the excessive system pressure can cause failures of the pump seals, wear on valves and components, excessive noise in the system, etc..

    Replace, or leave the relief valve in place, - and hire a boiler fitter who knows what he's talking about.
     
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