Jadnashua
Retired Defense Industry Engineer xxx
Download this document https://www.copper.org/publications/pub_list/pdf/copper_tube_handbook.pdf it will tell you more than you want to know about volume, pressure losses, maximum recommended flow rates, etc. If you go with pex, keep in mind that the fittings create more frictional losses than copper because the fit INTO the pipe, rather than around it like copper fittings, but the advantage is that you can probably minimize how many you need. For short distances, a pex fitting can act like a venturi, causing the water to speed up while going through the restriction (sort of like your finger over the end of a hose) and then slow back down again, without losing too much in pressure. If installed like copper, with elbows rather than just bending the pipe, you lose a lot of the advantages, add a lot of cost, and will create LOTS more frictional losses and volume issues.
A typical shower head sold can't flow more than 2.2gpm. A tub valve can flow 6-8gpm. The max recommended flow rate of 1/2" copper is in the order of 4gpm, but it will support more, depending on your pressure and you're getting supplied by both the hot and cold lines. Filling the tub while trying to take a shower is the issue if both are trying to pull from the SAME 1/2" pipe. If you branch off the 3/4" line with TWO 1/2" runs, you should maximize your performance with what you have coming in.
A typical shower head sold can't flow more than 2.2gpm. A tub valve can flow 6-8gpm. The max recommended flow rate of 1/2" copper is in the order of 4gpm, but it will support more, depending on your pressure and you're getting supplied by both the hot and cold lines. Filling the tub while trying to take a shower is the issue if both are trying to pull from the SAME 1/2" pipe. If you branch off the 3/4" line with TWO 1/2" runs, you should maximize your performance with what you have coming in.
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