plumbing

[bugmom]

I AM NEW TO THIS AND NEED A LITTLE HELP
WE ARE DOING AN ADDITION TO OUR HOME BEDROOM AND BATH
WOULD LIKE TO KNOW WHAT SIZE OF COPPER PIPE TO RUN TO A SHOW WITH
THREE IN LETS WE HAVE RUN 3/4 TO 1/2 WILL THAT GIVE US ENOUGH
WATER IN THE SHOWER??? WERE SHOULD THE VALUE BE????
ANYONE PLEASE!!!!!
BUGMOM1942@HOTMAIL.COM

[LazyPup]

Good Morning Bugmom and welcome to our forum..I am not certain what you mean by a shower with 3 inlets, perhaps you will be able to offer a bit more information on that. In the mean time i will try to offer some advice here.

The code minimum for a residential water supply line coming in from the street or well source is 3/4". The 3/4" is normally continued until it reaches the Water heater where the water distribution is divided into two separate but equal systems, the Hot and the cold.

From that point on it is run in 1/2" to insure an equal pressure on both hot and cold systems.

Pipe capacity is not determined by diameter but rather by cross sectional area, thus to determine the ratio of capacity one has to use the formula of the large diameter squared divided by the small diameter squared.

(3/4 x 3/4) / ( 1/2 x 1/2) =
(.75 x .75) / (.5 x .5)
.5625 / .25 = 2.25

thus a 3/4" line has the same capacity as 2.25 lines of 1/2".

Once the 3/4" supply has been reduced to 1/2" at the water heater both the hot and cold systems will have equal pressure and volume. Thus the lines from the water heater to the bathroom should be run in 1/2".

It is erroneously believed by some that if they increase the hot water line to 3/4" downstream of the water heater they will have less radiational cooling from the line but that is incorrect. Given that the pressure source is from a 1/2" line, increasing the line to 3/4" would increase the available radiational surface area while reducing the velocity of flow to 1/2 which results in a greater radiatonal cooling heat loss on the run of the pipe.

To effectively reduce the radiational cooling in the run of the pipe the pipe should be insulated for the full lenght of the run. In turn, the cold water line should also be insulated to reduce the possibility of condensation forming on the line and dripping in the basement, ceiling or in the walls, wherever the pipe may be run.