Where can I find a table showing flow volume for water pipe? I'm replacing two iron 3/4" pipes with a single line - a second floor bath & I"m replacing the hot/cold with just a cold supply then splitting and doing a point of use water heater.

Where can I find a table showing flow volume for water pipe? I'm replacing two iron 3/4" pipes with a single line - a second floor bath & I"m replacing the hot/cold with just a cold supply then splitting and doing a point of use water heater.

Well, it isn't as easy as all that.

Sizing a potable water system is much more involved.

A few variable a Plumber is required by code to consider are:

1) Pressure at the source/meter.

2) Distance from source/meter to fixture.

3) Pipe size of source/meter.

4) Elevation from source/meter to fixture.

And then of course each fixture is assigned a 'fixture unit number' depending on it's maximum draw.

It's basically an equation where you add up the fixture units being served and then use a chart that takes in the above numbered variables.

And if you're really anal about it, like I am, you also throw in the variable of friction loss added to the equation with each 90 degree change of direction.

This is the message:

Hello Speedball - I have a pretty simple question. What would you use to replace
Two 3/4" water supply lines. My guess is that 1 1/2" is too much.. .
I'm combining supplies to an upstairs bath, thinking I'll split and run the hot
Line to a tankless heater. The house is circa 1888 and existing pipes are iron,
I'll run PEX.
Thanks, aanji

If all you're supplying is three fixtures then I would keep the mains at v3/4". Our codes call for a 3/4" main with 1/2" branch with no more then three fixtures on a 1/2" branch. However, you might wish to run 1" up to the heater takeoff tee. Good luck, Tom

If all you're supplying is three fixtures then I would keep the mains at v3/4". Our codes call for a 3/4" main with 1/2" branch with no more then three fixtures on a 1/2" branch. However, you might wish to run 1" up to the heater takeoff tee. Good luck, Tom

>sticks out tongue<

Would you still recommend only 1" if the outlet of his source/meter is 3/4", the pressure at the source/meter is 35PSI, the distance from source/meter to the fixtures is in excess of 300 feet with a vertical rise of 45" from source/meter to the fixtures?

And one more fly in the ointment -- What would you recommend if his waterline is only a 3/4" feed?

>chuckles<

And what would you recommend if all of the above applied and one of the fixtures was a jetted whirlpool tub?

Sorry, this recently came up, and I had to turn a job down when the customer balked at installing a storage tank and pressurizing pump in his basement.:D