Can you run plumbing in exterior walls?

Steve J
Updated: Feb. 26, 2021

I am looking to finish a bathroom in my basement and would like to know if plumbing supply lines must always be run through interior partition walls or can they be brought to exterior basement walls that have been insulated using EPS + wood stud + mineral wool?

The interior basement walls have been insulated with 2" of EPS (R-10) and then wood studs constructed against the eps and filled with mineral wool insulation (R-14). Can plumbing supply lines be run to this wall assemble and down through the wood framing that is part of the exterior wall?

Does this go against the plumbing code or do I have enough insulation with the 2” of eps (and some of the mineral wool) to safely prevent any pipes from freezing? Should the pipes also be wrapped and insulated to assist with condensation?

Thank you.

Responses (1)

gary taube 3 years ago

NO.  NO    NO.   I bought a house in MI where the original owner did that.   A stretch of copper tubing was against the sill  with  branches up  into the walls for the bathrooms and kitchen.  One -30 cold snap and I had to replace several joints and faucets,  Also had to replace kitchen floor where it leaked under the cabinets and flooring.    I am working on moving the lines in, at least on joist away from the outer sill with lots of insulation.   I want the bathroom and kitchen lines in from the wall and lots of insulation in the walls.