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  • #16
    Re: copper water pipe system

    Anyone know of a reason why hot water recirculation systems cause copper piping to fail?

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    • #17
      Re: copper water pipe system

      I think it has to do with the ends not being reemed leaving a lip on the inside of the pipe, Then the recirculating system providing a constant flow of water past it.

      Another theory i've heard is that the lip causes the water to start a spiral eroding the pipe faster. Not sure how true this one is though.
      No, it's not rocket science, it's plumbing and unlike rocket science it requires a license.

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      • #18
        Re: copper water pipe system

        In most pipes, the water only flows when you use it. In a recirc system, the water flows continuously. Think Grand Canyon.

        I won't go too deeply into it because I'd get in over my head, but flowing water also generates the conditions for displacement in the metal. That's why we use dielectric unions between copper and other metals. However, it's become a consensus that dielectric unions are not all that effective and I've seen properly plumbed buildings with numerous copper failures. Our local courthouse has been a self-generating sprinkler system since it was built, while other copper-plumbed buildings have worked fine for a great number of years. We've been allowed to use M copper on residential plumbing here, so that's saying something.

        I've seen a lot of inexplicable failures on copper pipe here, and have long since decided that PEX is superior. Time will tell.

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        • #19
          Re: copper water pipe system

          When I said that hot water makes CPVC pipe brittle after a few years I didn't mean that it had anything to do with UV exposure. IT just gets very brittle sometimes and when you try to cut into it with ratchet cutters it will often snap and crumble. I know that the vast majority of guys use it to pipe in waters heaters down here, but I don't feel like getting a call at 3 am because some genius was pushing something into the hot line inside of their tight condominium closet. Noeettica is from Crystal Springs,FL which is about 1 1/2 hrs north of me. They used to/still do bottle water from the springs there so my guess is that the water in the area has a lot of minerals in it that the rest of us don't have....which probably effect the copper.

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          • #20
            Re: copper water pipe system

            Originally posted by drtyhands View Post
            I use timers and thermo-switches curently.I've got a friends restrictor I'm waiting for the opportunity to install.The problem I see with recirc's is a 1/2"(3/4" min.) return not reamed and running unnecessarily full time.
            A recirc line that is undersized will turn bad after a few years. We had an apartment complex that had all 1/2" recirc lines with circulating pumps. When we removed the leaking lines the pipe was as brittle as a dry twig. It turns out that when the 1" or 3/4" hot water distributing line transitioned to the 1/2" recirc line, the water velocity increases substantially and erodes the copper due to the impurities in the water speeding up and acting like sandpaper. We installed 3/4" copper recirc lines to solve the problem.

            The smaller the pipe the faster the velocity. With a larger diameter, there is less velocity to wear out the pipe. Water chemistry also plays a part in how long the pipe will last, but with recirc lines you have to watch the sizing to keep the velocity low.

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            • #21
              Re: copper water pipe system

              once the betina is worn off the undersized copper it is left unprotected thereby prematurely failing.

              oversized pumps are a problem as well.

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              • #22
                Re: copper water pipe system

                Originally posted by APHCO View Post
                It turns out that when the 1" or 3/4" hot water distributing line transitioned to the 1/2" recirc line, the water velocity increases substantially
                I think this is what we call the venturi effect.
                Last edited by bigPipe09; 01-29-2009, 01:40 AM. Reason: cant spell or type
                West Trail Mechanical Ltd
                Service. Commitment. Expertise.

                www.westtrailmechanical.ca

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                • #23
                  Re: copper water pipe system

                  Ok you guys are almost right, even some of the lowest flowing recirc pumps will pump almost 5 gallons a minute on a 3/4" line. The constant movement of water at that speed will not allow for a protective film called the "patina" to build up on the inner wall of the piping. Some of you are aware of the passive or gravity recirculating systems that have no pump at all but will do everything that a pumped system wiil do. The difference is that when these systems are cut into and a section of pipe is removed, no internal wear is noted. These systems are moving at a very slow speed yet they perform brilliantly. You want to solve your pin hole leaks on your hot water return lines? Slow down the velocity of the water. I have been doing this for years with great results. If any one is interested, private message me and I will e mail you some information on a product that I invented.

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                  • #24
                    Re: copper water pipe system

                    Originally posted by APHCO View Post
                    A recirc line that is undersized will turn bad after a few years. We had an apartment complex that had all 1/2" recirc lines with circulating pumps. When we removed the leaking lines the pipe was as brittle as a dry twig. It turns out that when the 1" or 3/4" hot water distributing line transitioned to the 1/2" recirc line, the water velocity increases substantially and erodes the copper due to the impurities in the water speeding up and acting like sandpaper. We installed 3/4" copper recirc lines to solve the problem.

                    The smaller the pipe the faster the velocity. With a larger diameter, there is less velocity to wear out the pipe. Water chemistry also plays a part in how long the pipe will last, but with recirc lines you have to watch the sizing to keep the velocity low.
                    couldnt u just add a ball valve or globe valve on the discharge side of the pump to slow the water movement through the pipe?

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                    • #25
                      Re: copper water pipe system

                      Originally posted by Dr. House View Post
                      couldnt u just add a ball valve or globe valve on the discharge side of the pump to slow the water movement through the pipe?
                      I think that would strain the pump.
                      No, it's not rocket science, it's plumbing and unlike rocket science it requires a license.

                      Comment


                      • #26
                        Re: copper water pipe system

                        Originally posted by Dr. House View Post
                        couldnt u just add a ball valve or globe valve on the discharge side of the pump to slow the water movement through the pipe?
                        I think that is called a balancing valve,usually installed on the circ line
                        it has a pointer needle in place of a handle, with ports for a flow meter
                        on each side of the ball ...also known as a circuit setter
                        I like it like that !
                        and, It's like that now!!!!!!!!!!!!

                        Comment


                        • #27
                          Re: copper water pipe system

                          Originally posted by drtyhands View Post
                          I use timers and thermo-switches curently.I've got a friends restrictor I'm waiting for the opportunity to install.The problem I see with recirc's is a 1/2"(3/4" min.) return not reamed and running unnecessarily full time.
                          i ve heard of tieing the circ pump into a motion sensor, in the bath
                          i've never done it,but i like the idea of it
                          i have seen,the circ line fool the lower stat, because it ran to long
                          I like it like that !
                          and, It's like that now!!!!!!!!!!!!

                          Comment


                          • #28
                            Re: copper water pipe system

                            Originally posted by Dr. House View Post
                            couldnt u just add a ball valve or globe valve on the discharge side of the pump to slow the water movement through the pipe?
                            As Rookie Plumber ( he doesn't sound like a Rookie to me!) is saying in the above post, a passive system won't have the trouble because the water is moving so slowly. Also,you save the cost of the pump, wiring etc. Another way would be to put the pump on a timer so that it is only operating at high usage periods.

                            The problem with installing a balancing cock in a recirc line is that you would not know how to set it, plus why go to the trouble. We usually install a 3/4" recirc line for residential usage without a pump and tell the customer to let us know if the water takes too long to reach the outlet. Never have had anyone call back for a pump.

                            I don't think I buy the point about the patina"protecting the pipe. I may be mistaken but I think patina refers to the change in color of a metal from aging or mild oxidation. I do not believe it protects the pipe from anything except further oxidation. Any metalurgists out there??

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                            • #29
                              Re: copper water pipe system

                              ok..i see why you dont use a circuit setter on residental
                              on comercial, the water is balanced..probes areinserted into the ports on the valve. he can read the gpms. and set the system accordinly
                              the air is balanced also...
                              bought a new home few years ago and the air needed to be balanced
                              the ac tech just pointed the registers, up a little
                              said i can come back and move em again,if they aint right!!
                              i just laughed,,and borrowed a cfm hood from work...
                              I like it like that !
                              and, It's like that now!!!!!!!!!!!!

                              Comment


                              • #30
                                Re: copper water pipe system

                                Dr House is on the right track but it is difficult to determine the return line flow from a globe valve and whenever a ball valve is used someone will always come by and say "hey who forgot to turn this thing back on" and your velocity reducing solution gets tossed out the door.

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