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Thread: recirculating loop to keep pipes warm

  1. #1

    Default recirculating loop to keep pipes warm

    As I mentioned in a previous thread we are putting in a new bathroom with a nice shower stall that will have two stationary shower heads and one handheld. We had a 40 gallon HW heater and just decided to updrade to a 75 (50 seemed silly and I guess for gas/regular vent unit there is nothing in between). Our plumber has offered to put in a recirculating loop so that we don't have to wait for the water to heat up in the shower (it takes maybe 15-30 sec, depending on the season). This setup doesn't use a pump but relies on hot water rising and cold water falling. He is already there doing the rest of the work (roughing in the shower stuff and replacing the hot water heater). The fee he quoted the contractor for this extra loop was just under $400 and the contractor would tack on another 80 or so. For $500 I think we can wait the 15-30 sec but I was curious about two things:
    1. Do these work?
    2. Does that sound like a lot of money for this sort of thing?

  2. #2
    DIY Senior Member finnegan's Avatar
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    The fee does not sound terrible, but it really depends upon a lot of facts such as how much piping, how many obstacles, etc.

  3. #3
    In the Trades Gary Swart's Avatar
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    I did some checking of ways of installing a reciculating system and this passive one was of interest. They will work only if installed in a basement. I ended up with a Laing recirculation pump which really works quite well for me. You may think that the time to purge the cold water from a line isn't significant now, but it gets pretty aggravating when you want to shower and have to wait 1/2 minute to get hot water. I really like waiting 1 second. There may be someone that can speak from experience on the passive unit, I can not.

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    Master Plumber master plumber mark's Avatar
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    Talking seems very high

    that is pretty high to just run
    a loop back to the heater...

    this does work, but waiting 20
    seconds isnt a big problem either.

  5. #5

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    Thanks for the replies. I am in the Boston area which likely jacks the price up. I was also wondering if insulating the hot water pipe would help, particularly in the basement which would be the coldest part of the house (though it's heated). Is that done?

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    Without insullation, you have a mini radiator. In most new construction, insullating the pipes is code; helps even with the cold pipes to help prevent condensation in the summer. If you use a gravity system, it will run all day every day. Insullate all pipes you can access without tearing out walls. My unprofessional opinion.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member DoofusOfTheDay's Avatar
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    Cheers,

    Gregg

  8. #8

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    Thanks Gregg, but I decided I don't want anything mechanical in there. So it's either the gravity/density recirc loop or nothing, with the latter most likely.

    Insulation question: are the pipes running in the floor insulated individually with some sort of sleeve or from the fiberglass insulation running between the floor joists (excuse my ignorance--is there even insulation between floors of a house?)?

  9. #9
    DIY Senior Member lithnights's Avatar
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    Quote Originally Posted by Gary Swart
    I did some checking of ways of installing a reciculating system and this passive one was of interest. They will work only if installed in a basement. I ended up with a Laing recirculation pump which really works quite well for me. You may think that the time to purge the cold water from a line isn't significant now, but it gets pretty aggravating when you want to shower and have to wait 1/2 minute to get hot water. I really like waiting 1 second. There may be someone that can speak from experience on the passive unit, I can not.
    Gary,
    Where do these things get installed? Basement? Bathroom? Can you (or anyone else out there) give a quick overview of how these actually work? e.g. what powers them, what pipes feed in/out etc? how much water is actually heated?

    Thanks in advance

  10. #10
    DIY Member jimmym's Avatar
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    A gravity recirc depends on a density differential. The only way to accomplish that is to allow the recirc line to cool itself off without insulation. (See code comment above). This also gets into the part about losing/wasting energy having that mini hydronic heater goin 24/7 even in the summer. That will generate more heat indoors and consume air conditioning dollars.

  11. #11
    In the Trades Gary Swart's Avatar
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    The Laing system I use is a pump installed near the water heater. You tied into the hot water line at the farthest point in your system and run it back to the pump. It requires the use of a check valve to prevent water from going the wrong direction, an air bleeder valve to exhaust the small amounts of air that may get into the line, a hose bib to expell air if the system has been drained, a cut off valve to shut the entire return line off. I removed the tank drain bib and replaced it with a nipple and tee with a valve to allow the tank to be drained and the return line. I used a flexible copper pipe (same as the intake/outlet on top of the tank) to make the last connection. There are two types of these pumps, one with a timer and one without. I have the untimed one. If you have access to the plumbing, and can sweat joints, it's not a difficult installation. You can go to the Laing web site and see a diagram of the installation and read about the various units they have. I got my unit on **** for way less than retail (new, in the box).

    A word about insulation. Remember, insulation will not warm or cool anything. It holds heat in or out. Just like a coat. So, insulate the pipes to keep the heat loss down.

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