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Water Pressure Test Prior to Drywall and Tile

Posted by syd81 (My Page) on
Fri, Aug 1, 14 at 11:41

I'd like to test the water pressure in my new bathroom before I button up the walls. I ran 1/2 water lines and worry that the flow might not be enough. I figure I can sweat a fitting on the end of the shower lines that will accept a gauge, but I thought I would check here first to see if there is some standard or recommended method I have not heard of. What do you think?


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RE: Water Pressure Test Prior to Drywall and Tile

It occurs to me that pressure is not the same as volume or flow in this circumstance. Capping the line creates a closed system and the pressure will be the same throughout. So how do I measure flow? Run the water into a bucket for 1 min and then measure how much? Any help would be apreciated.

This post was edited by syd81 on Fri, Aug 1, 14 at 12:58


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RE: Water Pressure Test Prior to Drywall and Tile

You are correct, you cannot measure the flow rate the way you proposed in first post.

You won't get a good approximation without the finished fixtures in place. Most of them have flow rate restrictors.

You probably need to look at what size pipe, how long, how many el's to come up with a pressure drop for a given run. That will give you a better idea


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RE: Water Pressure Test Prior to Drywall and Tile

is this a "new" bathroom or a remodel of an existing?


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RE: Water Pressure Test Prior to Drywall and Tile

It is a new bathroom. I ran the lines myself and didn't consider running 3/4 at the time - only later to read about problems with long runs. It is a second floor bath.


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RE: Water Pressure Test Prior to Drywall and Tile

Would it be a matter of hooking up the fixture, measuring the gpm, and then comparing it to the manufacturer recommendation?


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RE: Water Pressure Test Prior to Drywall and Tile

How long is the run, how many elbows, how many fixtures, what kind of pipe (pex, copper, CPVC)?

Short of doing the math... you may run into an issue if have multiple fixtures (shower, sink, toilet) on a single half inch run. What you will have is the shower changing temp when the toilet flushes, for example. Half inch is usually fine for single fixture in residential applications.

As far as a single use- you are most likely to see any problem in the tub - where the flow isn't restricted.


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