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Protecting PEX from abrasion on wood tray and in blind fish run

jsavage Member Posts: 42
edited May 2020 in Plumbing
Hi all,
As you can see in the pictures, these water lines on the 2nd floor are run in a retrofit manner which required creating an access door in the floor. The ceiling under is ornate plaster, so I’m sure that was the best option when they did the retrofit about 80 years ago. I am replacing these particular pipes with PEX because I’m concerned with the l ead content in the old brass lines.

As you can see in the attached photos, the current brass pipes sit on a wood tray that has been built into the floor. They are not attached to anything (no hangers/brackets) for their entire length. Furthermore, this tray runs about 12’ under a carpeted area where I do not want to pull up the carpet.

What is the best way to protect the PEX on this run?

I’m concerned about abrasion sitting on the wood tray, and in particular abrasion in the part where I can’t access it to install any sort of hangers or standoffs.

My current thoughts are to install regular hangers in the part that I can access and use some sort of a sleeve, such as pipe insulation or PVC, to protect the pex for the section where I need to snake it blind. I’m unsure if this is necessary though. Thoughts?
Homeowner from Providence, RI
Home b. 1897, one-pipe steam with a indirect gravity hot air system using Gold's pin radiators.


  • STEVEusaPA
    STEVEusaPA Member Posts: 6,506
    Thoughts...where are the pictures?
  • Jamie Hall
    Jamie Hall Member Posts: 23,275
    The outer layer of PEX is pretty darn tough. I've pulled a good bit of PEX through some pretty horrible chases, and honestly I've yet to see a significant problem. PEX tubing is generally rated at 100 psi at 180 F. Presumably, if you are concerned about lead, these are domestic water lines, so your maximum temperature would be around 149 F -- so the rated pressure would be somewhat greater. Your domestic water shouldn't be over 60 psi

    Bottom line: unless you put a big gouge in it, or drive a nail into it, you shouldn't have a problem.

    Being in a wood tray is a big advantage. PEX, unless it is continuously supported, will sag.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • jsavage
    jsavage Member Posts: 42
    Ok I added the pictures. Sorry for that!

    Jamie thank you for your help. As I thought more about it after posting yesterday, I realized that the issue with abrasion is more about a lot of pressure on a single point, and no point would actually have that much pressure if it was continuously supported on the tray.
    Homeowner from Providence, RI
    Home b. 1897, one-pipe steam with a indirect gravity hot air system using Gold's pin radiators.
  • Sal Santamaura
    Sal Santamaura Member Posts: 529
    edited May 2020
    I've nothing useful to add about PEX, but am reporting that my wife walked by just as I brought up your second picture and she let loose with intense ooohing and aaahing over the dog. :)
  • hot_rod
    hot_rod Member Posts: 22,110
    Or add some pipe insulation.

    It is important to fasten the tube as a fast acting valve or faucet can cause it to jump around. I have one tube in my office that I fed across a sheetrock ceiling to a sink. Every time we shut off the faucet we get a bump.

    I suppose a small hammer arrester under the sink would handle it, but do the best to keep the tube fastened.

    Many of the pex brands offer a sleeved pex, supposed to be used when pex is in the ground or slab for water supply.

    Also the next size up pex can be used as sleeves, 1/2 goes into 3/4, 3/4 into 1"
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • jsavage
    jsavage Member Posts: 42
    Thank you all. I’m going to fasten at each end of the run and will slip some foam insulation along the length of the pipe (as I wanted to do that anyways for HW recirculation).
    Homeowner from Providence, RI
    Home b. 1897, one-pipe steam with a indirect gravity hot air system using Gold's pin radiators.