(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 15 of 32

Thread: Hot Water Recirculation Choices

Hybrid View

  1. #1

    Default Hot Water Recirculation Choices

    If it's not too expensive, I want to install a recirculation system for the master bathroom of our remodel, which is about a 45' pipe run from the water heater. I estimate we would have to wait about 35 seconds without recirculation before hot water would appear. (Kitchen and downstairs bath are very close to the heater.) Pipe is 3/4" L copper. I'd like to not waste water or have to wait a long time for hot water to appear, but I also don't want to pay for something that would take 10 years to recoup the cost.

    There are 2 choices which are intriguing to me.

    1. Gravity fed convection system. This should work since the water heater will sit in a utility closet at ground level, first floor is 2 feet higher above a crawl space, and master bath is on second floor. My understanding is that we need a 3/4" return line from upstairs with the whole loop insulated EXCEPT for 15-20' at the end of the return line (just before the water heater), and that this cooler section is what sets up the convection flow–albeit a slow flow, which I assume is good. If this doesn't work, it may be necessary to install a check valve going into the drain side of the water heater, and if THAT doesn't work, can I assume that a recirculation pump can be installed retroactively? My contractor is not experienced with gravity-fed systems.

    2. Contractor recommends a (new) product that he has used in his last 3 houses. It uses a pump but does not require the installation of a return line. Somehow, the hot water at the end of the line trickles into the cold water side. Does anyone know what this product is and what might be the pros and cons?


  2. #2
    Moderator & Master Plumber hj's Avatar
    Join Date
    Aug 2004
    Cave Creek, Arizona

    Default circulation

    1. If the contractor is not proficient in gravity systems do not even consider it since it has to be "engineered" to very strict guidelines, and ALL the plumbing has to be higher than the water heater.
    2. Forget about ever recouping the cost of a circulation system. The added fuel costs, electricity to run the pump, and shortened heater life will add to the long term costs, not reduce them.
    3. Those systems are not a panacea. They give "warm" water initially, but still have some lag for "hot" water, and the cold water faucet may have an initial spurt of warm water.

  3. #3
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    If you have the option of installing a return line, by all means do so. This will eliminate some of the side effects of the retrofit pump systems. Remember to insist on complete insulation of hot lines.

  4. #4

    Default Recirculation followup

    Thanks. Actually, the lowest plumbing line is in the top section of the crawl space and would be still above the drain spigot of the tank although not the main body of the tank itself. The water heater will sit on a pad 2 feet below the first floor. Does this count as "above" the water heater?

    Also, I assume the luke warm water to start and some initial warmth from the cold tap refers only to the systems that use the cold water supply as a return. Are products like the Grundfos Comfort Series or Taco D'Mand systems meant for retrofit situations where installing a dedicated return line would be too difficult and expensive? Are there other problems with using the cold water supply as a return that I should be aware of?


  5. #5

    Default I'm installing a Grundfos today

    I'm actually installing a GrundFos Comfort Series pump today. I'm actually doing it not for instant hot water, but to stop some very inaccessible pipes from freezing (slight circulation of hot water should prevent freezing, that's the idea anyway). I bought mine new on **** for $175 which was much cheaper than I could find from a plumbing supply store.

    Installing it seems to be a snap. It connects right above your water heater on the hot side. On the bottom of the pump is a connector to attach to the 3/4" male on the water heater. At the top of the pump is a 3/4" male. I have 3/4 copper into my heater, so I had to cut about 6" off, sweat a 3/4 female and I was done with pump install. Now, I'm installing the comfort valve on my bathroom faucet which should be very easy.

    Taking a lunch break right now, or I'd be done. If you're interested, I'll try to get back to you with a report on how it works. BTW, there's a couple threads from a couple months ago about this topic.

    Good luck,


  6. #6

    Default Recirc pump

    Thanks Andy. And yes, I'm interested in hearing your results although I have given our remodeling supervisor the go-ahead to install a third 3/4" copper line as a dedicated hot water return line. The walls are completely open now; they won't be in a couple days. Normally, I believe he uses the Grundfos Comfort Series and leaves out the third return line, but overall, the cost of the third line is only slightly more. Don't know which system is more cost effective to operate; having a dedicated hot water loop (entirely insulated but is double the length of the Comfort Series that dumps its hot water into the cold water supply for the return).

    By the way, I've confirmed that these lines come in from ABOVE the water heater if we were to try giving a gravity fed system a shot. How hard could it be? Plumber recommends installing a pump from the outset in order to be on the safe side–and to avoid $150 or so of retrofitting costs later. Also, uninsulated 15' of pipe at the end of the return line might be inaccessible after drywall goes up, and I guess we'd want full insulation if we did NOT end up using a gravity-based convection system.

    Thanks again,



Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts