Recommended plumbing pipe material for ADU?

Question

Hi,

My friend is building a ~600 sq ft ADU in So Cal/Los Angeles and is wondering what type of pipe might be best from a quality/maintenance/cost standpoint within the interior of the ADU (I realize that the line connecting the ADU to the sewer line might be HDPE or some other plastic pipe...)?  Apparently there are five basic types of plumbing pipes per this article with copper being fairly common.

Matt Devincenzo · Answer

New build apartments generally use PEX or CPVC for supply and PVC or ABS for vent/waste. You can price out and combo of those two to determine the lowest cost option. I would personally use PEX for supply becauce it comes in long runs with no fittings. DWV would be fine either way.

Sonny Vu · Answer

Hi Bruce. The choice of pipe material for residential (including ADU) should be left up to the plumber. If you have a specific need or want, you should let them know and they will decide which is best in your situation. I'm not a plumber but recently took a plumbing course so please verify on your own. That said, supply pipe and DWV will be different. Supply piping is usually copper or pex. Drain,waste,vent(DWV) piping can be ABS, PVC or cast iron, depending on your specifications. Cast iron is usually used in commercial and multifamily applications due to durability and cost. Plumbers will know what material to use for your application.

Dan H. · Answer

Sewer/vents are ABS/PVC.  The old cast iron sewer pipes lasted 50+ years but they are heavy, labor intensive and ABS/PVC is a much better option (and I expect AB/PVC to last as long as the cast iron).  We have replaced the cast iron sewer in many of our properties.

Copper where my units are located (hard water location) typically gets its first leak at between year 35 and year 50.  It seems like we have a slab leak to address every year and some years multiple slab leaks (our last one (just prior to Covid) destroyed the kitchen cabinets because it went unnoticed because the cabinets were absorbing much of the water).

PEX in my view still has the verdict out at expected lifespan.

PEX is much easier installation than copper.  I would go with PEX for the supply lines.  I personally expect it to last longer than copper in hard water locations, but this is largely speculation.

Good luck

Bruce P. · Answer

thank you @Dennis Maynard and @Matt Devincenzo - and to answer your ?, yes I will be hiring a professional, I'm just trying to learn as much as I can to help manage the project, so any details appreciated.

Dennis Maynard · Answer

fresh water lines should be copper.  Sewer line should be ABS.  Pretty simple.  are you hiring a plumber?  They will know the answers.

Recommended plumbing pipe material for ADU?

Most Popular Reply