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DHW Recirc. Pump Systems


A while back I built an addition that includes a master bedroom with a master bath. Since then, it has been a guest room but now that the kids are older we are getting ready to let them have the upstairs and we are going to move into the first floor master. When the addition was built, I had the plumber install a 1/2" PEX line for recirc. use eventually. The bathroom is at the opposite end of the house from the Buderus Boiler/DHW Tank and there is about 90' of 3/4" PEX that runs to the bathroom and 90' of 1/2" PEX for recirc.

I'm now looking for suggestions on the best recirc. pump to use. My preference would be to install the pump at the DHW tank. It seems that all of the major players have pumps with smart controllers so I'm wondering if anyone has had good/bad luck with any specific brand. The bathroom will mostly be used in the morning and evening so I'd prefer to not always be circulating hot water and wasting heat.

Any ideas or suggestion would be appreciated. You were all hugely helpful when I replaced my boiler 5 years ago and every contractor wanted to way oversize it!!

Many Thanks.



  • Dave H_2Dave H_2 Member Posts: 417
    Perfect, perfect, perfect in every way to add recirc. Your pipe lengths and size are very close to what I have installed in my home.
    I put in the SmartPlus circ for the exact reasons you stated above, not wanting to wait and to not let the circ run needlessly when hot water is not needed.
    The SmartPlus is designed to be installed at the water heater and has a temperature sensor that will learn your patterns of water usage and will run during those time periods only. It also only "pulses" when running. When it learns an event (water usage) it will "run" for about two hours around that time because not everyone uses water at the exact time every day so it gives you that window of opportunity. So for that two hours, it will pulse which means run for 2.5 minutes, off for 10 minutes, on for 2.5 minutes.......

    Now since you have one water heater and are only concerned with the one bath, if you can get the sensor as far down the supply hot water line toward that bath, it will not get confused by the other uses of hot water in the house.

    If you can't get the sensor on the pipe far enough down, then you can consider the Genie system which is user activated by a button switch or motion sensor. Again the circ is installed by the water heater and the button or motion sensor is installed in the bath. These are hard wired back to the circ. If wiring is an issue, there is a wireless button option to add.

    Dave H.
    Dave H
  • JUGHNEJUGHNE Member Posts: 7,910
    If your water heater is in the basement.....there is a good posting on Dec 2016 entitled "Anyone Try?"......worth the read....covers a little of everything.
  • Brent H.Brent H. Member Posts: 89
    Thanks for the info. I noticed that pumps are available in Bronze or Stainless, which should I be looking at? If it matters, I'm on well water with a softener. Also, how do I best size the pump since I have 3/4" supply but only 1/2" return? And lastly, does anyone have a good diagram of how to connect it into a HTP SuperStor? I thought there was one in the manual but couldn't find it.

    Thanks again.
  • Brent H.Brent H. Member Posts: 89
    Can anyone help with my followup questions above?

    Many thanks.
  • hot_rodhot_rod Member Posts: 14,411
    Stainless is replacing bronze in most DHW pumps. Less expensive and easier to get the low lead approvals.

    Here is an Idronics issue on water heating. Towards the back we explain recirc piping, pump sizing, etc.

    If you have a thermostatic mixing valve in the system, pay attention to the recirc piping detail with an adjustable bypass that needs to be adjusted.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Problem is you can't sweat Stainless. You installers of DHW recirc - how would you feel about a recirc with a press connection?
    delta T
  • IronmanIronman Member Posts: 6,175

    Problem is you can't sweat Stainless. You installers of DHW recirc - how would you feel about a recirc with a press connection?

    I'd love to see it.

    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Dave H_2Dave H_2 Member Posts: 417
    Very interesting when it comes to DHW circulator connections. A couple of years ago, I had posted a survey asking which connection was a preferred method and I had exactly all four result in at even.
    If you all would like to participate in that survey, the article and survey (at the bottom) is here

    Dave H.
    Dave H
  • hot_rodhot_rod Member Posts: 14,411
    A union body pump, with a 1" G thread would allow for virtually any connection and easy swap out.

    Most of the world already uses union bodies so they are currently available in many sizes and materials like cast, SS, poly, bronze.

    In addition to threaded, sweat and press, grip, PP, PVC, pex any adapter could be used. Checks could be added also.

    That same nut and tail also fits zone valves, mixing valves, balancing valves, etc etc.

    It makes it easier on the wholesalers, stock one body on any pump or product and select the connections desired.

    One size gasket fits all also, no more hunting for the correct ring gasket as every brand is different.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Brent H.Brent H. Member Posts: 89
    I'm still in search of some help with determining the proper pump size assuming 90' of 3/4" PEX supply and 90' of 1/2" PEX for the recirc. line.

    Also, looking at the diagrams in the Idronics magazine, it appears all I need is to Tee in the recirc. pump with a check valve in-line with the pump. Is a recirc. pump with an IFC adequate?

    Thanks for the help.
  • Dave H_2Dave H_2 Member Posts: 417

    Take a look here, this chart shows either one way or total amount of pipe used to size your circ. The 003 will get you what you need, however the 006 is more common and about the same price.

    Or for a more extensive read click here

    Dave H.
    Dave H
  • Not a fan of the union fitting. Potential additional unnecessary leak paths and typically the union pump thread is not a normal US thread (a lot of BSP and parallel threads).
  • Brent H.Brent H. Member Posts: 89
    I think my thread has been hijacked :smiley:

    Is the IFC sufficient for this application or should I use a separate check valve?
  • Dave H_2Dave H_2 Member Posts: 417
    The IFC is sufficient, we offer them both ways depending upon new or replacement. New, use the IFC; if replacement and the system already has a separate check, then non-IFC needed.
    Dave H
  • Hey Brent - your are correct, I hijacked your thread, sorry about that. Snuck in to ask about connection types on DHW circs (couldn't resist).

    Our Dave Holdorf training guru guy (sorry if I sound biased) has got the thread back on track. Thanks Dave - see you in Vegas...
  • hot_rodhot_rod Member Posts: 14,411

    Not a fan of the union fitting. Potential additional unnecessary leak paths and typically the union pump thread is not a normal US thread (a lot of BSP and parallel threads).

    I guess I'm not seeing a "potential additional unnecessary" leak path in these two pump connection options?

    With either, a fitting or flange needs to be installed on the pipe or tube. Solder, press, what ever.

    With flanged pumps you need to have the correct bolt pattern flange, as larger circs require larger flanges.

    With a flanged circ you need the specific OEM gasket or a universal flat gasket. Taco, B&G, Armstrong, Grundfos, Wilo, Aqua Motion, Honeywell all have different sized, non compatible ring gaskets.

    With a union pump any round gasket will work with any brand or style of pump. Even a hose washer works in a pinch. a piece of flat gasket material becomes a ready made gasket with a couple pieces of copper tube and a hammer. Or tin snips. :)

    With a union pump, and a new gasket, hand tightening is often all you need.

    Worldwide that 1" G thread is probably the most common threaded connection.

    Pretty much any 3 way thermostatic valve, 1/2- 1 uses a 1" G connection

    Most 1/2- 3/4 PRVs. many zone valves, balance valves, fill valves, all 1" G.

    It wouldn't be that hard to get the pumping industry to all start a movement to union connections. If you shop pumps from Euro manufacturers, for example, they much prefer you select union bodies, and can offer a wider range of options, and it is now on a global platform.

    Just as PSC motors are phasing out, so should two bolt, flanged

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • HillyHilly Member Posts: 412
    I always thought the G union was sharper looking compared to a standard BI Flange set and I guess they'd provide swivel ability to every installation. @hot rod is there anything in G unions that will equal the compact/neatness of a isolation flange product. I do think a lot of the specialty flanged fittings when needed or used properly make life much easier and are quite the space savers.
  • hot_rodhot_rod Member Posts: 14,411
    There are iso unions in Europe, probably metric size however.

    Webstone and others could easily build an iso purge union valve. Just a different tailpiece in their current valves.

    Maybe I'll prototype one :)

    Several thousand solar pump stations have been sold here in the US under various names, they all have union circs either Wilo or Grundfos. Already a replacement market is growing, and we stock several different union pumps for that market.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream

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