If you lived alone, only using one plumbing fixture at a time – correct pipe size wouldn’t be a big issue. However when you are in the shower and someone flushes the toilet – it is a big deal. The basic rule is two fixtures on a 1/2″ pipe. You need min. 3/4″ incoming cold pipe for a one bath house. Just running 3/4″ to each fixture in the house won’t hurt, but there will be no real gain. To size a water distribution system, get a copy of your state code book. It will spell it out in terms of beginning pressure, the furthest fixture from the meter and the number of fixtures in the house. Each fixture is worth so many units and you are allowed so many units for each size pipe as you get further from the meter. Be aware that this isn’t really a DIY job – you definitely should have help from a licensed plumber to design and install your plumbing system.

2 Comments

  1. Lynn

    I recently bought a house in Wi and noticed that although there is 3/4″ copper pipe from well pump unit in basement to the hot water heater the copper pipe coming out is only 1/2″ copper pipe. What I don’t recognize is a strange looking copper enlargement in this line within 8″ of tank after a 180 degree turn in the pipe. I think it might have something to do with the pipe size reduction but don’t know. And if I replace the hot water heater is this enlargement necessary?

    Reply
    • plumbergirl

      Hi Lynn,

      Sometimes plumbers do things that make a lot of sense at the time or solve the problem at hand – but that may confuse homeowners or other plumbers later on. Without being on the spot and examining the plumbing system, it is difficult to say whether or not the enlargement is necessary when you replace the water heater (or even why it is there in the first place). We would recommend you visit our plumber friends over at Plbg.com, where you can post pictures and get some free professional advice about dealing with your specific situation, or contact a local plumber for help determining what you need. Thanks for visiting us here at thePlumber.com!

      Reply

Leave a Reply

Your email address will not be published. Required fields are marked *