IRC Plumbing Table WSFU (Max Velocity in PEX Piping)

[omoreno80]

I typically size of my water supply lines for both commerical and residential structures using WSFU. Does anyone know the maximum pipe velocity and assumbed pipe materials used in the IRC plumbing section? I have compared the values to the NSPC and those tables (based on different piping materials) appear to be totally different. I am looking at PEX piping in particular and for a limit on pipe velocity. The tables in the NSPC have velocity ranges from 4 to 8 ft/s. Can I assume the higher 8 ft/s for PEX piping in residential structures? I am a structural engineer, with some experience in this but by no means an expert on pipe flow. If I need to brush up on my Moody chart, please let me know. Thanks

 

[kepharda]

I am sure 8 ft/s would be fine, for PEX, but I really try to avoid blanket statements when determining piping losses.

This is because it depends on the length of run you are considering, heck 15 ft/s isn't a problem if it is only for a foot or two.

For the longer runs I would shoot for 4 ft/s, because you also need to consider a diversity factor on all the lines. (ie water heater, and a couple of sinks on all at once). This is why shooting for the lower velocity will keep you out of trouble.

Plus typically with PEX we are talking about small piping so stepping up a size really can really decrease your velocities without a substantial increase in cost.

this message has been approved for citizen to elect kepharda 2008

 

[zekeman]

If you are working with PEX, you might look at some useful design information here.

http://www.toolbase.org/PDF/DesignGuides/pex_designguide.pdf