View Full Version : Pipe Sizing for Half Bath

09-23-2005, 10:16 AM
I will be running Type L soft copper for both hot and cold supply to a half bath on my second floor. I'm replacing the existing 3/4" galvanized.

The total distance of the run will be less than 40'. I am planning on using 1/2" for hot, as the lav will be the only fixture on the run. As for cold, I'm not sure if I should use 1/2" or 3/4". 1/2" would be adequate based upon fixture units, but I'm wondering if I'll get any added benefit from going with 3/4" (i.e. better water pressure while washing hands while the toilet tank is filling).



09-23-2005, 11:11 AM
If you have normal water pressure, the 1/2" will in fact be fine. However, your added cost for running 3/4" will not be much greater and it will give you more volume. Though, you end up with more dead water in the pipe so that if you want cold, cold water, you need to wait a little longer for it. I run 3/4" risers and then run 1/2" to the fixtures. With the soft tubing you will save yourself some time with less couplings, but it can be a little harder to keep the cut ends round which can make it a little harder to solder.