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Recirculating loop

MpjMpj Member Posts: 109
Roughing a house with six bathrooms on three floors. The owner wants a hot water recirculating loop. Each bathroom will home runs (PEX) from the boiler room to each bathroom. Looking for opinions on how to do. I was thinking run a 1/2" PEX line to each bathroom, looping at the basin or in the floor and back to the boiler room, Connect each loop to a manifold and to the indirect heater. I will be using a Buderus GB boiler which has a connection to turn the recirculating pump on/off a timed intervals

Any comments would be great.



  • icesailoricesailor Member Posts: 7,265
    HW Recirc:

    That might work for you.

    What always worked for me was to go to the farthest bathroom (hopefully, the master bathroom) and connect back to the source with a tee connection. Then, use a "Make On Fall" Thermostat like a 4006B control to sense when the water gets cool. An adjustable timer so you can set time for it to run. AND, an over-ride switch that is like a fan light timer that automatically shuts off after running for how long set. The timer has to be powered all the time and NOT through the over-ride switch.

    The Master Bathroom is the room that gets the most hot water use. If the hot water recirc. normally comes on at 6:00 AM, and you get up one morning at 4:00 AM to take a shower and get cleaned up for a 6:00 AM flight, you just turn on the timer switch. It shuts off before you are out of the bathroom. You need the "Makes On Rise" control to shut  of the circulator when no one is around to be using water.

    If it is a new house and it is on a well with really cold water and sweating toilets, install a toilet tempering valve that will automatically mix hot water with the cold and stop the water from getting to the dew point and sweating. If you install mixing/tempering valves on ALL the toilets, you won't need a re-Circ line because a simple flush of a toilet will bring the hot water to the bathroom. And you won't get call backs to take up what the customer thinks is a leaking seal on the toilet. Which never is. Its a sweating toilet.

    A customer will never be satisfied until you take up the sweating toilet to fix the seal that some home/DIY show has told them that the sweating is due to a leaking seal. Then, you try to convince them after taking up the toilet that it isn't the seal. They insist that you put TWO on. Or one with a plastic horn, that makes them flush poorly. When the sweating and water don't stop, they think you're an idiot because you can't stop a leaking toilet. The uncompensated time spent would have paid to install a tempering valve. And you get the added benefit of false hot water circulation. In over 40 years, I NEVER installed a toilet without a Tempering valve where it was new construction or a renovation. If it's old work, and there's a vanity cabinet next to the toilet, its easy to install a mixer.

    Happy customers are paying customers.
  • hot rodhot rod Member Posts: 7,014
    Some piping ideas and schematics here

    Will the indirect tank have a thermostatic mix valve on it? if so be sure you pipe the recirc pump correctly (page 53)

    If you pipe multiple loops to different areas of the home you may need some balance valves to adjust flow.

    Insulate ALL the HW piping!

    Really what the recirc system provides is just enough flow to overcome the heat loss from the recirc loop piping. Both the timer and a thermostat are a good idea, as Ice mentioned.

    Sounds like the boiler has the timer function, a small "snap on" thermostat is available from Grundfos and other circ pump manufacturers
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • icesailoricesailor Member Posts: 7,265
    That will work:

    That will work.

    If you give them the price, you might need to be schooled in the Heimlich Maneuver.

    If that's a possibility, add my way to the price. It might have some benefits. Sometimes, low technology has its place.
  • jonny88jonny88 Member Posts: 1,139
    re circ line

    I posted same question a long time ago.I used Hot Rods drawing,system works a charm.Very interesting what Icesailor points out,I never worked on well water but what great advice,think this guy has a trick for everything.
  • icesailoricesailor Member Posts: 7,265
    Mother's Inventions:

    Necessity is the mother of inventions.

    When you're the 4th one called for s problem and no one has figured it out, stubborn pride makes us go that extra inch to solve it. And we are getting paid to learn.

    How many new (for us) customers have we gone to and seen a recirc pump running 24/7 and not pumping water? Because the Impellor on a Taco 006 if worn completely away? Or, the switch has been off for years? No one complained.

    In the Northern Latitudes, every hardware store sold drip pans to go under the toilet tanks of two piece toilets to catch the sweat and stop floor rotting because of clod inlet water. Raise the incoming water above the dew point and it won't sweat. Install a tempering valve to get the water above the dew point and flush the toilet. You get warm water to the toilet while getting hot water to a faucet for use.

    Another example is that in "ancient" times, China, The Fertile Crescent and Europe/Asia, domesticated animals, Pigs, goats, sheep, horses and cattle, They also developed uses for the wheel. Moving things on wheeled carts. In the America's, there were no large animals to domesticate except for Llama's in South America. For wool, meat and transporting small amounts of goods. But never to pull wheeled carts. The only evidence of the wheel being used in the America's was a child's toy with wheels made like a cart. They had no large animals to pull it. Until the Spanish arrived on horses. Which the Indians quickly stole and put to good use. Africa has the highest diversity of large animals. Not one was ever domesticated.

    I used to work with a guy that always had things backwards. Some of his backwardism's stuck, Our favorite was "If there's a way, there's a will". Ponder that one for a moment.
  • Larry WeingartenLarry Weingarten Member Posts: 1,173
    structured plumbing

    Hello:  Here's a  link  to an article written by Gary Klein on how to build a really efficient distribution system that will deliver hot water to any tap in seconds (1-2 cups of water).

    Yours,  Larry
  • MpjMpj Member Posts: 109

    Thank you all for your responses.

    Ice, I have done the recircs before with an aquastat in the master vanity to keep the water a pre-set temperature. I do not think it would work well with bathrooms on three floors and with a home run distribution system.

    Hot Rod,I like drawing 7-5, I could add balancing valves on the manifold and thermometers on each loop back from the system. Can you tell me what the purpose of the bypass (#1) is for? I see no need for it..

    Thanks again
  • icesailoricesailor Member Posts: 7,265
    Running home with manifolds:

    If all runs to fixtures are home runs to manifolds in the cellar, how can you have any re-circ lines?

    If you have a large building with the mechanical room on one end and a large master bath on the second floor at the other end, how do you save money with home runs back to a manifold somewhere on the first floor. How do you recirc the hot water fixtures?
  • MpjMpj Member Posts: 109


    I should said it a different way. Each bathroom will have separate hot and cold water supply piping from the boiler room. Each set of water lines will have isolation valves in the boiler room as per contractor request. He also wants a recirculating loop to each bathroom. This was the only way I could think of doing it. Sorry for the misunderstanding.
  • WeezboWeezbo Member Posts: 6,232
    maybe this thought will help.

    Hot Rod,I like drawing 7-5, I could add balancing valves on the manifold and thermometers on each loop back from the system. Can you tell me what the purpose of the bypass (#1) is for? I see no need for it..

    Thanks again

    when you take something out then you need to put something back.

    were there no return to the heat source there would be heat going out and sooner or later it would dissipate. the anti scald benefits from some warmer water being allowed into the recirc system mixing with hotter water as that reduces the time and hastens the response thru the mixer.

    when i need recirc the easiest way i find i use. Often i catch a t branch at the most remote bring it past the next branch t and pick up something like a washing machine box branch as the last fixture .

    that gets hot water to the fixtures and as the washing machine doesn't complain ,

    should that fixture have the hot water side open it will carry on without too much further to do , as the water makes the long loop.

  • hot rodhot rod Member Posts: 7,014
    Hi Weezer

    the purpose of the bypass and throttling valve is to allow a small portion of recirc to go back into the tank. When some flow goes into the tank, you push some hot water out and into the "H" port of the 3 way. The mix valve needs to have a differential to operate properly and accurately.

    Also the loop will lose some temperature as it goes around and around, even insulated loops. The goal of the recirc loop is to assure the last fixture see water temperature within a few degrees of what it leaves the mix valve, 5- 10 degrees is what we suggest ∆T from mix valve output to temperature at distant fixture.

    As the loop loses temperature, you need to push a small amount of hot from the tank to replace that heat loss, hense the bypass. If not eventually the loop loses all the temperature

    Think of how a non-insulated loop causes the tank to fire, sometimes too often.

    A recirc loop is just a mini hydronic loop. The pump should be sized the same way, temperature drop and piping head.

    An example in Idronics11, page 51

    100 feet 1" copper, 100 feet 1/2 copper uninsulated.

    135F at tank 10 degree drop= loss or 4800 BTU/hr. (shows how important insulation is)

    .96 gpm required, pressure drop of 1.6 feet. A tiny circ, by hydronic standards :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • GordyGordy Member Posts: 7,106

    No one does it anymore when piping, and layout lends itself?

    My home is gravity recirc works well. Obviously this has limited applications.
  • hot rodhot rod Member Posts: 7,014
    Dave Yates

    has written some good articles on gravity recirc dos and don'ts. Heck we used to heat entire buildings with gravity HW flows.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • icesailoricesailor Member Posts: 7,265
    Defying Gravity:

    It certainly does. With only a minimum of a 7.5 degree F. differential in temperature. With a little flapper in a check valve to stop it, or a little speck of debris to allow it to happen,

    As long as it basically flows up and doesn't have any serious droppy places (heat traps) it will flow to its heart's content. Like all things gravity, it likes room to move around. If you use a circulator, you can contain it in a smaller space and force it around.
  • MpjMpj Member Posts: 109
    Recirc loop


    Are you suggesting that I run a pipe from each bathroom/sink location back to the water heater and tie it in with not check valves, circulators?
  • GordyGordy Member Posts: 7,106
    In your case

    No with a home run install.

    Usually you would run a return from farthest fixture only back to water heater.
  • MpjMpj Member Posts: 109


    Thanks for your reply. That is the usual way I also do it. This one has got me.

    I really haven't seem a answer to my question just some good ideas. I'm going to install a pump on the return manifold back into the water heater and incorporate part of Hod Rod's suggestions
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