My basement apartment's hot water pipe runs starting with 3/4" from the heater to the first outlet, the bathtub and the 2nd one, the washer. From the washer, it goes to the bathroom sink (please don't question this design as I have structural reasons why it doesn't go from the bathtub directly and don't want to spend time explaining as it's not pertinent) and ends in the kitchen sink, which will also be supporting a dishwasher.
My question is, can I run only 1/2" pipe for hot water starting from the washer, will it be enough bandwidth or should I go with 3/4" ? I know that some people have up to 3 outlets out of a 1/2" copper pipe but I'm not sure how to count the DW as it is a different appliance but using the same valve from the wall inside the counter. I have run 3/4 to the tub and to the washer and now I'm about to continue on from the washer towards the bath and kitchen sinks and need to make a design decision.
Best Answer
According to Uniform Plumbing Code Table 6-5 (610.3), the Water Supply Fixture Units (wsfu) per fixture in a private residence are as follows:
So you're supplying 3 wsfu.
According to Table 6-6 (610.4), at 30-45 psi you can supply 3 wsfu with ½" pipe with a developed length of up to 100'. 46-60 psi you can have a developed length of up to 200', and greater that 60 psi can go up to 300'.
At 40' or less with 30 psi, ½" pipe can supply 6 wsfu. So with a short run, you should have no problem using ½" pipe.