Help with copper pipe size


Old 01-10-10, 08:14 PM
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Join Date: Mar 2009
Location: Missouri
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Help with copper pipe size

Hot water
Existing hot water copper pipe coming from water heater is 1/2". This supplies four fixtures: washing machine, bath sink, shower/tub, kitchen sink.
I am adding a basement bath and will need to add three more fixtures: utility sink, bath sink, shower.

I need to upgrade to 3/4" copper pipe from water heater correct?

Cold water
Pipe coming into the house is 3/4" until it reaches a reducer T.
The Pipe going to water heater is 3/4", but the rest of the pipe is 1/2".
Existing 1/2" cold pipe supplies water to five fixtures: washer, toilet, bath sink, shower, kitchen sink.
I need to add four more fixtures because of the basement bath: utility sink, bath sink, toilet, and shower.

Is it necessary to upgrade to 3/4" before they branch to each fixture?

Any guidelines will be helpful. I currently have nine lines total (hot & cold) with no problems with water pressure.
With the new basement bath and laundy reconfigure, I will be adding seven more lines (hot & cold).

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Old 01-10-10, 10:46 PM
Join Date: Aug 2003
Location: KY/OH
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The golden rule is as follows:

3/4" from the main to the water heater, from there to the fixtures shall be 3/4" with branches down to 1/2".

3 on hot, 3 on cold when it comes to 1/2" pipe.

So as long as you bring 3/4" to this equation, you'll be in good shape.
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