What size pex should i run?

My current line coming into the house is 1/2" copper. From there it goes into old 1/2" steel pipe. I am adding a new bathroom and am going to take out as much of the old piping as possible as well as add a manifold so i can easily shut off certain fixutres.

If i go with 1/2" pex would i be okay? or should i go with 3/4" since i heard 1/2" inside diameter is smaller than 1/2" copper is.

If I were going to do this (note, I'm not a pro), I'd do it as if it was a new house and use the current guidelines. Eventually, you'll probably want to replace that 1/2" line into the house with one that meets current codes and you don't want the new stuff you did in the house to not benefit from that increased supply. So, I'd use 3/4" to major groups of fixtures, then switch to 1/2" to the valves. Now, if you plan or have a big tub or a multi-head shower, you may want to run 3/4" all the way to that valve. the washing machine can benefit from the larger lines as can hose bibs to the outside even if you reduce it to 1/2" at the valve itself.

k i my father was urging me to go with 3/4" as well. That chart made it very easy to agree with him and the other posts.


Thanks guys