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1/2" supply line from road, what to do inside?

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  • 1/2" supply line from road, what to do inside?

    So I want to upgrade the plumbing in my house/rental unit. I'd like to replace much of the old galvanized stuff with copper. The problem is this...the supply line coming into the house is 1/2" copper. It runs through the water meter and then into 1/2" galvanized. Obviously this isn't ideal. Not much I can do about the supply line, however, I'd like to run 3/4" for the mains through the house and then 1/2" coppy lines to each individual unit. Question is this.....what will happen if the supply line is 1/2" and I run the mains through the house with 3/4". Will the pressure be high when the water is turned on at the faucet and then immediately drop as the 3/4" pipe is emptied and slowly filled with the 1/2" supply?

  • #2
    If you run 3/4 inch mains from a 1/2 inch feed it will not drop of in pressure as soon as you turn on a faucet. It will be the same as if you had 1/2 inch supply throughout. But with that being said i think it would be a good idea to run 3/4 supplys so that one day you could change your supply line coming in to the house and not have to re do anything else.

    If you are having a problem with pressure right now you might be suprised how much of an improvement you will have when you get ride of the excisting galvanized pipe. I have seen a 3/4 inch galvanized water line restricted to the point of only a slow trickle going through it.

    If your still having a problem with pressure you can add a pump and pressure tank on your house supply. This is would help pull more water through your 1/2 water line. this is illegal in my area but people still do it sometimes. Even just a pressure tank (bladder stlye) alone would help a bit.

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    • #3
      In many of my multifamily projects (4plexs etc...) the water service is 1" and we up size to 1 1/4" to the 1st and 2nd suites, 1" to the 3rd and 3/4" to the 4rth.

      In your situation I think it would be beneficial to run a 3/4" cold supply and 3/4" to the water heater. You really only need to run 3/4 to the first fixture (hot and cold) and then 1/2" from then on. If you want you could run the cold 3/4" all the way with 1/2" branches but not the hot.

      Also, you should consider a home run system (pressure compensating manifold distribution) like Wirsbo,Rehau,Kitec etc...
      You will never expand your mind, if you do not challenge your beliefs.

      By the reading of this post, you acknowledge and agree that the poster shall not be responsible or liable, directly or indirectly, for any damage or loss caused or alleged to be caused by or in connection with use of or reliance on any content contained herein.

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      • #4
        You don't run 3/4" hot water lines as a main...ie....3/4" to the hot water heater, and continue with 3/4" line after the hot water heater....then T off with 1/2" to each individual fixture? I thought that was what you did with both hot AND cold water.....

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        • #5
          If you want to waste your money and wait forever for hot water go ahead
          Last edited by Hondahead; 01-05-2007, 08:37 PM.
          You will never expand your mind, if you do not challenge your beliefs.

          By the reading of this post, you acknowledge and agree that the poster shall not be responsible or liable, directly or indirectly, for any damage or loss caused or alleged to be caused by or in connection with use of or reliance on any content contained herein.

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          • #6
            Why "waste your money"?? Will the hot water come to the fixtures quicker if it is 1/2" ??

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            • #7
              ...because it is basically 1/2" now, and it takes FOREVER to get to the fixtures around the house....

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              • #8
                Up sizing the water heater supply line to 3/4" will make a difference. Over sizing the hot distribution line will result in higher water heating costs and increased wait time for hot water. (Think about it, the volume of water sitting in the line when not in use will cool and then when you turn the tap on you'll have to wait as the luke warm water clears.) With water flow you have a few things to consider such as pressure,volume and velocity. At equal pressure and volume the velocity in a 1/2" line will be greater than 3/4". Of course your current sytem takes for ever to get to the fixtures around the house.Do to the deterioration of the piping,calcium/magnesium build up etc your old galvanized 1/2" piping is probably the equivelent of 1/4" or 1/8" piping by now.
                Last edited by Hondahead; 01-05-2007, 11:12 PM.
                You will never expand your mind, if you do not challenge your beliefs.

                By the reading of this post, you acknowledge and agree that the poster shall not be responsible or liable, directly or indirectly, for any damage or loss caused or alleged to be caused by or in connection with use of or reliance on any content contained herein.

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                • #9
                  Hondahead and Keqwow,

                  How about sizing the water lines based on plumbing code requirements. You know, that strange book that we plumbers are supposed to follow because it is law.

                  I'm hearing alot of opinions being spread here based on no engineering principals. Come on guys, there are homeowners who look for answers here. I don't help them because I think that free advice takes work away from ligit. plumbers. But to maintain our reputation on this site, so we don't turn into the "Terry Love" site, we need to show some standards.

                  In my opinion, and that's all it is, give some back-up to your answers. Base it on code or engineering principals. Not: "this is what we normally do".
                  the dog

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                  • #10
                    In this situation the minimum code requirement of a 3/4" water service has not been met. Now its just a matter of what will work best to remedy this situation. I am only trying to help this guy out and give him real advice as to what will work and why. I am not going to take the time to explain code or engineering principals, if he wants to learn that he can go to school like I did.

                    Originally posted by plumbdog10 View Post
                    In my opinion, and that's all it is, give some back-up to your answers. Base it on code or engineering principals. Not: "this is what we normally do".
                    What "I normally do" is engineered according to code, not my opinion.

                    Opinions are like $h!t, everybody gives theirs and they usually STINK!
                    You will never expand your mind, if you do not challenge your beliefs.

                    By the reading of this post, you acknowledge and agree that the poster shall not be responsible or liable, directly or indirectly, for any damage or loss caused or alleged to be caused by or in connection with use of or reliance on any content contained herein.

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                    • #11
                      So what is code for hot water distribution lines running AFTER the hot water heater?

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                      • #12
                        Originally posted by keqwow View Post
                        So what is code for hot water distribution lines running AFTER the hot water heater?
                        Keqwow,

                        I'm not sure what the requirements are in New York, you would have to check with your current code. In the UPC section 610.1 requires all potable water lines to be sized by fixture demand.
                        the dog

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                        • #13
                          NPC code 6.3.1 "using a detailed engineering design method"

                          The water service (minimum 3/4") is sized by the total number of cold water fixture units as determined from tables 6.3 and 6.3.2 (fixture demand) , the total developed length from property line/public water main/source to the most remote outlet, difference in elevation from source to highest outlet and supply pressure. Using this information and table A-6.1 will determine the water service size. To size the distribution pipes you start at the most remote outlet and work back toward the water service (cold lines) or water heater (hot lines) using the total developed length and adding fixture unit values from tables 6.3 and 6.3.2. as you go.

                          Your existing system was "engineered" to use 1/2" pipe throughout.
                          You will never expand your mind, if you do not challenge your beliefs.

                          By the reading of this post, you acknowledge and agree that the poster shall not be responsible or liable, directly or indirectly, for any damage or loss caused or alleged to be caused by or in connection with use of or reliance on any content contained herein.

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                          • #14
                            I'm with dog here. How can you tell the man what size lines to run without knowing what the lines are feeding and what his supply pressure is? Would you recommend the same pipe sizing for 15 psig as you would for 80 psig? It sounds like he is interested in fixing the problem so I don't think it does him any service to feed him faulty info.

                            Mark
                            "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                            I never lost a cent on the jobs I didn't get!

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                            • #15
                              Originally posted by ToUtahNow View Post
                              I'm with dog here. How can you tell the man what size lines to run without knowing what the lines are feeding and what his supply pressure is? Would you recommend the same pipe sizing for 15 psig as you would for 80 psig? It sounds like he is interested in fixing the problem so I don't think it does him any service to feed him faulty info.
                              WTF? Its common sense not rocket surgery! Did you spend the time to read the previous posts?

                              Maybe insted of knocking me for trying to help a brother out you could take the time to give your suggestions on what he could do?
                              You will never expand your mind, if you do not challenge your beliefs.

                              By the reading of this post, you acknowledge and agree that the poster shall not be responsible or liable, directly or indirectly, for any damage or loss caused or alleged to be caused by or in connection with use of or reliance on any content contained herein.

                              Comment

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