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wallport 06-18-2010 07:35 AM

pex piping
 
how do you size pex piping, when installed in a traditional method like a copper system which incorporates tees for branch connections?

..some manufacturers reference the Uniorm Plumbing code or national plumbing codes but some do not make a reference....they recommend the Home Run method.

The Engineer 06-18-2010 07:55 AM

Its sized pretty much the same way copper is sized, based on fixture unit counts and how many fixtures each leg of the system serves. Also taken into account are distances, available pressures and elevations. The only difference between copper and pex, is the friction loss co-effiecient when determining the pressure available for friction loss.

Piedmont 06-18-2010 09:15 AM

The reason copper has size limits, is because water flowing through it at high velocities wear it out and it can be very loud.

For cold water, copper pipe shouldn't have a flow of greater than 8 feet per minute and for hot water 5 feet per minute.

How that affects PEX I don't know I think it would have a different set of rules.

Daniel Holzman 06-18-2010 09:28 AM

Piedmont, you need to check your units. The flow you quote would be in feet per second, not feet per minute. And copper can certainly handle more than 8 feet per second, its simply that at higher velocities you get greater pressure loss in the pipe, and hence lower pressure at the fixture. Standard tables for copper pipe typically show losses up to 25 feet per second for applications where pressure loss is not significant.


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