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Thread: SURVEY: Recirculating Pump and Leaks - How many years?

  1. #1
    DIY Junior Member proxybox's Avatar
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    Default SURVEY: Recirculating Pump and Leaks - How many years?

    Hi. I had a problem with a Grundfos recirulating pump causing wear on the return hot water line on two properties and causing pinhole (pin-hole) leaks.

    1. I want to find out how many of you, plumbers and DIY's, are experiencing the same problem?

    2. What did you do to solve the problem.

    I want to find out how extensive this problem is.

    Thanks,

    Jon

  2. #2
    In the Trades Bob NH's Avatar
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    I would check the following for evidence that might point to the cause of the failures:

    One problem with hot water recirculating pumps is that they are sometimes oversized and produce very high velocities in the pipes for very long durations. What is the flow/head curve for the pump, and what is the flow rate at the head that exists? What is the size of the pipe? What velocity in the pipe? How many hours per year do the pumps run?

    Are there any signs of erosion at the locations of the failures when the failed pipe is sectioned and the inside surfaces inspected? Is there any sign that the protective films are damaged by erosion at local areas?

    Are there any materiels such as sediment from the water heater that could be circulating and causing erosion?

    How far from the pump are the failures occurring? On the inlet or outlet side of the pump?

    Are there any signs of corrosion at other locations near the pinholes.

    What type of pipe? Copper L or M?

    What are the materials in the pump and pipe, and in the water heater. Are there any dissimilar materials that could contribute to electrolytic corrosion?

    What is the pH of the water? What temperature?

    Is there any treatment that could have altered the chemistry of the water?

    Is there anything about the location of the failures, such as at elbows or reducers or bends, that might give a hint as the cause of failure.

    Are the failures associated with support points where vibration might be causing damage?

  3. #3
    Moderator & Master Plumber hj's Avatar
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    Default leaks

    It is usually because of excessive velocity. Install a globe valve, stop valve, balancing cock, or whatever they are called in your area, (not a ball or gate valve), between the pump and the water heater, (and definitely not ahead of the pump). Then start turning it down until the pipe just stays warm. At that point you have the minimum flow to keep the system hot without exceeding the velocity needed to do it.

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    DIY GUY JUAN MONTOYA's Avatar
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    Hi i read your response in 2007 to leaks. i too am having pinholes on the hot return side at a T-or elbows of the fiting .You stated that you should reduce the velocity of hot water recirculation pump by turning down the valve. Do you mean at the inlet side or outlet?

  5. #5
    Moderator & Master Plumber hj's Avatar
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    OUTLET side, NEVER on the inlet. You will starve the pump and create cavitation which will destroy the pump.

  6. #6
    DIY Junior Member proxybox's Avatar
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    Default I used x10 switches and timers to reduce the use to on demand

    I purchased x10 remotes, an appliance switch module and controller (www.x10.com) and placed the remotes in each bathroom. I programmed the modules to turn on for 3 minutes and activate the pump. After 3 minutes the pump shuts off. I found this solution to be pretty elegant since it limits the amount of wear on the return pipe to when it is needed.

    I had an issue where the pump would not always turn on. I did a little research and discovered that I needed to bridge both sides of my circuit breaker box. Frorm my readings it turns out that some surge power strips, stereo receivers, computers, utility transformers, etc suck up the signal. I purchased a simple cross switch/amplifier on x10 and all is perfect. I have been using this system since the time I posted the survey.

  7. #7
    Moderator & Master Plumber hj's Avatar
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    quote; I did a little research and discovered that I needed to bridge both sides of my circuit breaker box

    You have to do that when the modules are on different legs of the 240 supply line and the transformer is too far away for the signal to "crossover" through it. I just attached a capacitor between two of the circuit breakers to solve the problem.

  8. #8
    Jack of all trades DonL's Avatar
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    What value cap did you use to bridge the signal hj ?

    I just make sure my controllers are on the same circuit that I am controlling, and reliability is much better.

    Have a Great Day.

    DonL
    Theory only works perfect in a vacuum.

    Cyber Security Protection for Windows C:\ > WWW.WinForce.Net

  9. #9
    Plumber jimbo's Avatar
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    depends on the frequency of the x10 system. I am thinking you would use something in the range of .01 UF/370V ???

  10. #10
    Jack of all trades DonL's Avatar
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    Yes jimbo I think .01 is about correct.

    I like using 1KV caps, work good and last longer.

    Being on the same circuit is better.

    X10 stuff is marginal anyway. I would not use it for a critical device, unless I had a backup.

    To many things work on the same frequency, and power spikes false them, ON/Off.

    Have a great day.


    DonL
    Theory only works perfect in a vacuum.

    Cyber Security Protection for Windows C:\ > WWW.WinForce.Net

  11. #11
    DIY Junior Member TomWS's Avatar
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    We've set up our circulator pump in a similar way and rely on the timer function in the controller to turn on the circulator only during our 'normal' demand hours. We can also use the wireless remote when needing HW during off hours.

    To get around X10 unreliability in our large house, we've placed X10 filters at all our computer and home theater equipment and installed an XTB-IIR signal booster. HUGE difference in reliability. The capacitor/inductor bridges work ok where the wiring runs are short and there aren't too many signal 'gobbling' loads, but, if you want X10 reliability, boost the signal and filter where necessary.

    Tom

  12. #12
    DIY Member jadziedzic's Avatar
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    Bell & Gossett sells a recirculating pump with an adjustable thermostat (Eco-Circ e3 series) that can accommodate an optional plug-in timer (the pump has an electrically-commutated motor that uses very little energy). If the hot water lines associated with the pump are well insulated (as they should be), the pump should run very little, which should in turn result in less chance of erosion.

  13. #13
    General Engineering Contractor ballvalve's Avatar
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    The very moderate flow through pipes, copper or pex from even the highest head 1/12 or 1/4 hp Grunfos circulator CANNOT cause pinhole leaks.

    Such holes are caused by water chemistry, not flow rates.

    30++ radiant systems, copper, polybutylene and pex, 2 to 5000+ feet each, 30 and less years old, and no leaks in my experience.

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