Obviously none of the people who have responded have even a remote clue about how to properly size a line. When designing a potable water distribution system you begin by selecting all the end use fixtures to determine what the end use load will be. In the case of the original post they want a shower head, body sprays, a hand shower and possibly a rain shower head. Quote:"How many fixtures will you have on at any one time? Remember that 3/4" pipe has double the capacity of 1/2" pipe." Code requires that we design a potable water system for a worst case scenario. The system must be capable of maintaining the code listed minimum fixture "Dynamic head pressure" even when every fixture in the house is turned on at the same time. The statement that a 3/4" pipe has twice the capacity of a 1/2" pipe is not true. The capacity, or properly the volume of flow is determined by the size of the metering orifice in the end use fixture. It is true that a 3/4" line has double the cross sectional area of a 1/2" line however both will supply the same volume, the difference being that the velocity of flow will be twice as fast in the 1/2" pipe. The problem here is that as the velocity of flow increases the "fiction head pressure loss" increases dramatically. In addition to the loss of pressure due to friction head if the velocity of flow exceeds 8fps we start seeing sever pipe wall erosion, which leads to premature pipe failure. In fact, while acidic water is the leading cause of pin hole failure in copper pipe, excessive velocity in undersized pipe is the second leading cause of pinholes. Preferably we should have the end use fixture data available when designing the system but in situations where that information is not yet available we use the gal/min flow rates that are published in the code. Now getting back to the original question. All the end use fixtures in question are types of shower heads and per code shower heads are restricted to 2.5gpm so let us begin putting it all in perspective. Using the code standard of 2.5gpm we get shower head (2.5gpm), hand shower (2.5gpm) and body sprays (2.5gpm)equals and a hand shower(2.5gpm) for a total load of 10gpm. Consulting the "Type L Copper Friction Loss Table" we find that if we supply this shower with a 1/2" line the velocity of flow would be 13.80ft/sec and the pressure loss would be 67.72psi/100ft of pipe. If we increase the pipe size to 3/4" the velocity of flow is 6.62ft/sec and a pressure loss of 11.17psi/100ft.

GOOD GRIEF!!! I knew you were getting a bit more than us, but I sure didn't expect THAT much more! We got 2.5 in our rain gauge. The storm must have had some major pockets of rain in it, we got more than Fred did...in town! LOL Hopefully you got all the water in the basement cleaned up and it didn't do any damage.

Lots of brilliance in this collection, in a wide range of fields. McGahern is more conventional, it seems to me. All others were leaders in their field, dedicated to upset apple-carts. Elisabeth Cady-Stanton is still vilified by many emales, all I can say: when will many of us ever learn? Thank you, Don.

I second Anneliese...I am glad that I am not First for once (smiling) particularly because I am still in early morning and the First up of Coffee and my mind is sort of frozen.