Good morning,

Hoping this is a quick and easy answer. I'm running pex and have received very mixed info as to just how to properly size stud penetrations. I had planned simply to up size 1/16 to 1/8" to pipe OD and go from there, ie the half inch pex through 11 or 12/16" bored hole. I had one person tell me that SOP is to double the diameter of the pipe - so 1/2" should run through 1" bored holes. Finally a second person said grommets must be used in studs, joists etc (which Im fairly certain is not true for wood members) and that the whole should be 1 3/8 to accommodate the grommet.

Any insight? A quick attempt to get a solid answer to this seemingly basic question yielded nothing. I know there can be intense lateral expansion along tubing, but wasn't sure about my narrower hole plan the more i thought about possible expansion.

Here is what one well-known pex manufacturer says about pex installation. The person that suggested hole inserts or grommets to you was probably thinking about metal studs, you wouldn't want the metal stud hole's sharp edges cutting into the pex as it flexes when water flows thru it.

(download & view 12 page guide by clicking here)

[images.ewins.com]






Edited 13 times.

My view is that you can err by undersizing, especially with PEX, but oversizing won't hurt provided it's not overboard.

i usually drill 3/4 holes for short runs of pex thru studs. the last hole before changing direction 90 deg, i drill a bit larger and angle it at a 45 toward the way it is turning.

Packy your 3/4" holes are for 1/2" pex, correct? That's likely what I will go with, is echoed by the NibCo installation manual

I actually received an answer from Sharkbite, that did not answer the question specifically. Here's their response for reference for anyone else:

****Hi, there isn't necessarily a suggested size. Our recommendation would be to use one some type of insulation to protect it from rubbing up against the wood repeatedly through the stud. Hope this helps!***

Most of my runs are fairly short, 5-20' anyone think the grommets to avoid abrasions are needed?

no sleeving of pex is necessary when going thru wood..