1/2″ meter water supply – can I go to 3/4″ trunk line?

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    • #276560

      Hi all. I have an 45 yr. old home fed with a 1/2″ city water supply into my water meter. I am going to replace the entire copper supply from my side of the meter onward throughout the house and am now wondering what the reprecussions would be if I expanded the new trunk line to 3/4″, thinking that I might gain better flow.
      My question – would I encounter flow or pressure problems with the 1/2″ feeding the 3/4″ trunk? Or would the 1/2″ starve the 3/4″? Or am I simply stuck with having to supply the whole house with 1/2″ supply throughout? It would be nice to have better flow to support my existing fixtures more adequately and have less competition when multiple fixtures are being used. Currently my pressure seems about adequate (or a little less), probably standard 40 p.s.i.
      Please help me with this flow/pressure dilemna!
      Cheers; Red

    • #294383
      Retired plbg1

      You would have more volume stored in the pipe but the same pressure. As you use it the volume would decrease. Look into a well tank installed on your line and run 3/4″ from there. I used one on 12 story building for temp water to toilets.

    • #294384
      Retired plbg1

      You might look into pumps too. They have come out with some new ones, check in a search for the pump.

    • #294385

      Red ,why not run a new water service to the house? Then you would have everything new when you change all the inside water lines.Chances are sooner or later you are going to have to replaced the service any way and it isnt going to get any cheaper. Why mess around with pumps, tanks etc.You will spend alot of money for all this equipment and then the service leaks and you have to fix it ,then you have all the equipment sitting around that you dont need.

      » This message has been edited by racefanone on 04 May 2003

    • #294386

      Red, you ask a very good question. A suggested, the best solution is to have replace the line from the meter with a larger diameter one (3/4″). You didn’t say what size line the water company has running INTO your meter/curbstop. On some old houses, that inlet may be 5/8″ or 1/2″. If so, you can ask the company to upgrade your water service (at a small cost…they will then bill you at a different and higher rate).

      Even if you are stuck with a 1/2-5/8″ municipal supply line, there is definite benefit in going to a 3/4″ line to supply your house. As was pointed out, the VOLUME of H2O (and hence the FLOW, which is defined as volume/minute) in your supply lines will be greater. The main limitation in such a setup will be PRESSURE. You will see a pressure drop when you move to a larger line from a smaller one. Here is where you need to be aware of the hydrodynamic calculations and trade offs.

      IF your service pressure is adequate, you can get away with larger lines to your fixtures, and any drops in pressure will be compensated by better flows.

      Not to mention the benefit of replacing old and calcified galvanized pipe with smooth bore copper lines…


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