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PEX vs. Copper or other materials for 1920's Steel Supply Pipe Upgrades?

cubicacres Member Posts: 358
We were wondering about what options are available if we decide to replace some or all of our 5 unit apartment building water supply pipes that are mostly 3/4in. steel from the 1920s with about 20% copper upgrades that occurred over the years.

We've heard PEX can install faster and is cheaper than copper, but were wondering if there are trade-offs compared to copper pipe or another material like CPVC, etc. Our city plumbing inspector says PEX & CPVC are locally approved and popular, so we were curious abut our options.

We have a 2 story apartment building that was built in 1900 with steel pipe that may have been originally installed in 1929 when the addition was put on and the basement expanded that has the supply pipes running through it from the basement ceiling up to the apartments.

The main and first 40 feet with the 2 40 gal. hot water heaters is copper, so we're thinking of keeping it and adding PEX if that's better than scrapping it to go 100% PEX. We have access panels for each apartment (kitchen sink, bathroom shower, bathroom sink & toilet) & pipes running up inside some closets & crawl spaces we can access, so that helps.

Any thoughts on trying PEX vs. Copper?


  • Jamie Hall
    Jamie Hall Member Posts: 23,415
    The only problem I've had with PEX vs. copper is that with PEX you have to be somewhat careful with horizontal runs so that they are properly supported -- otherwise, in time, they sag. Other than that the stuff is great, particularly for retrofits, as it can be pulled into places where it would be dang near impossible to get new rigid (or even soft) copper. As to mixing the two -- no problem. Just get the right fittings. So I'd replace the steel with PEX, and keep the copper.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • cubicacres
    cubicacres Member Posts: 358
    Thanks! Steam, water heaters, plumbing...is there anything you guys don't do? :)
  • Steamhead
    Steamhead Member Posts: 16,885
    Before deciding on plastic piping, you need to see if anyone has used the existing piping as an electrical ground. This is rather common in older buildings where the existing wiring was not grounded, as with knob-and-tube or older Romex wiring.

    If it has, and you aren't ready to rewire the building, stay with copper.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service