Announcement

Announcement Module
Collapse
No announcement yet.

passive recirc

Page Title Module
Move Remove Collapse
X
Conversation Detail Module
Collapse
  • Filter
  • Time
  • Show
Clear All
new posts

  • passive recirc

    Just a bit of curiousity on my part. If I had a tanked NG water heater, with a recirculating loop tied in at the bottom with the drain cock, when the system wasn't being actively used, would the water rising as it was heated be enough to draw the cooler water from the recirc line and create a passive system?

    This is an idea I was kicking around actually trying on my own home, but the idea kind of got nixed when I started shopping for an outdoor mounted tankless.
    No, it's not rocket science, it's plumbing and unlike rocket science it requires a license.

  • #2
    Re: passive recirc

    my buddy steve did it all the time on his repipes. as long as you hot water run is brought to the upper floor and returned to the lower floor heater. you need to also have a blow down valve to completely bleed all the trapped air and drill a 1/8'' hole in the check valve.

    works like a charm 24/7 without all the wear and tear on the system.

    i have a 12 unit condo building where the 100 gallon heater is in the ground level garage. the hot main runs in the ceiling of the second floor of the 3 story building.

    the 25 year old building was constantly getting pin hole leaks in the circ system.

    2 choices. repipe the line that runs between the floors or turn off the circ pump.

    turned off the circ pump and the system still naturally circulates. the pump is still there, but not plugged in. this was done several years ago and than a bad solder joint at a 90 in the garage, there have not been anymore leaks

    why do you want to install a tankless

    rick.
    phoebe it is

    Comment


    • #3
      Re: passive recirc

      If you are insulating the return line, leave the drop to the heater bib uninsulated. Helps draw the heat through the line.

      Comment


      • #4
        Re: passive recirc

        Originally posted by MoJourneyman View Post
        Just a bit of curiousity on my part. If I had a tanked NG water heater, with a recirculating loop tied in at the bottom with the drain cock, when the system wasn't being actively used, would the water rising as it was heated be enough to draw the cooler water from the recirc line and create a passive system?
        Yes.

        Comment


        • #5
          Re: passive recirc

          Originally posted by PLUMBER RICK View Post
          why do you want to install a tankless

          rick.
          in short, space, I can get a tankless that mounts outside of the house on the back wall, that also repositions the heater between the kitchen and bathroom, instead of at the furthest possible point from the bathroom.

          I'd have rather installed a nice large tanked water heater, and done a recirc system, but i'd need to move the tank out of the laundry room and into the garage, which is fine until I trade the girlfriends Focus in for the Outback she's been eyeing.


          also, thank you everyone for the replies, this ideas been stuck in my head for a few months so it's nice to hear that it would actually work.

          Drilling the pinhole in the checkvalve, is that for a swing or spring check?
          No, it's not rocket science, it's plumbing and unlike rocket science it requires a license.

          Comment


          • #6
            Re: passive recirc

            That would be a 1/4" hole on a swing check valve. One more thing, on a lot of water heaters (Bradford White) there is a heat check insert that is pushed into the hot outlet nipple on top of the heater. You must remove this with a pair of needle nose pliers or the system will not work at all. Other heater manufacturers have similar devices that must also be removed to allow for circulation.

            Comment


            • #7
              Re: passive recirc

              yeah, the heat trap nipples, those always looked rather restrictive to flow anyway.
              No, it's not rocket science, it's plumbing and unlike rocket science it requires a license.

              Comment


              • #8
                Re: passive recirc

                Would someone review why you drill a hole in the check valve. Never heard that one before, and have had gravity recirc systems work properly with the check valve but without the hole.

                Comment


                • #9
                  Re: passive recirc

                  Originally posted by APHCO View Post
                  Would someone review why you drill a hole in the check valve. Never heard that one before, and have had gravity recirc systems work properly with the check valve but without the hole.
                  I have NOT done it much but some say that in the right situation you sometimes can't get the convection engine? going even though you've purged, insulated, uninsulated etc.

                  Put a small hole in the swing and it gets it going and functioning properly.

                  J.C.

                  Comment


                  • #10
                    Re: passive recirc

                    Originally posted by APHCO View Post
                    Would someone review why you drill a hole in the check valve. Never heard that one before, and have had gravity recirc systems work properly with the check valve but without the hole.
                    The movement of the water in a passive system is not enough to open the check. I have also seen where a ball valve is used instead of a check to throttle the flow of the recirc.

                    Comment


                    • #11
                      Re: passive recirc

                      Originally posted by APHCO View Post
                      Would someone review why you drill a hole in the check valve. Never heard that one before, and have had gravity recirc systems work properly with the check valve but without the hole.
                      not enough flow to lift the swing

                      Comment


                      • #12
                        Re: passive recirc

                        There are several reasons for drilling a hole but first you have to look at the benefits provided by the check valve. Water like electricity follows the path of least resistance, a plumbing fixture or bathroom that is on the return loop in close proximity to the heater will pull it's hot water supply off the bottom of the tank resulting in luke warm water very quickly as the cold water coming down the dip tube will be mixing with the existing hot before exiting the heater at the bottom. The check valve keeps this from occurring. In my early days I could not get a passive loop (gravity system) to work well with a standard swing check valve unless I installed it almost on it's side. The drawback was that when the hot water was shut off from a fixture being used the check valve would slam shut sending a shock rebound throughout the system resulting in an offensive "clunk". Drilling the hole allows you to install the check valve in it's proper position, does not promote water being drawn off the bottom of the tank and reduces debris from the bottom of the tank congesting stems, it also remedies the clunking noise.

                        Comment


                        • #13
                          Re: passive recirc

                          Originally posted by rookie plumber View Post
                          There are several reasons for drilling a hole but first you have to look at the benefits provided by the check valve. Water like electricity follows the path of least resistance, a plumbing fixture or bathroom that is on the return loop in close proximity to the heater will pull it's hot water supply off the bottom of the tank resulting in luke warm water very quickly as the cold water coming down the dip tube will be mixing with the existing hot before exiting the heater at the bottom. The check valve keeps this from occurring. In my early days I could not get a passive loop (gravity system) to work well with a standard swing check valve unless I installed it almost on it's side. The drawback was that when the hot water was shut off from a fixture being used the check valve would slam shut sending a shock rebound throughout the system resulting in an offensive "clunk". Drilling the hole allows you to install the check valve in it's proper position, does not promote water being drawn off the bottom of the tank and reduces debris from the bottom of the tank congesting stems, it also remedies the clunking noise.
                          Do you have basements in your working area? Perhaps the reason we ( in the North) do not need to drill the check valve is that there is enough temperature differential as well as vertical distance between the basement and the second (usually) floor to create the needed flow. Not having any "up" would limit gravity circulation.

                          In some of the much older homes the hot water heating was by gravity, no circulating pump but large diameter piping. They worked well, slowly, but well. Without a basement they would not have worked at all in a single story home. A hot water recirc line would be under the same constraints.

                          Comment


                          • #14
                            Re: passive recirc

                            i use to drill 1/8'' holes in the cold inlet check valve of large raypack and larrs domestic boilers. this was back in the days when expansions tanks were not installed and without the hole you had the potential of thermal expansion since the entire building was new with no leaking fixtures.

                            the hole allowed for the thermal expansion to equalize with the cold water inlet pressure and regulator bypass feature.

                            without the hole, you had a leaking relief valve.

                            rick.
                            phoebe it is

                            Comment


                            • #15
                              Re: passive recirc

                              I have run a gravity circ line that had only 3 ft of rise on a 40 ft run and then the return dropped down 3 ft and ran parallel under the feed line back to the heater before dropping down to the bottom of the tank. Worked great for many years.

                              Comment

                              Working...
                              X