I'm running a cold-water pex line in a basement crawlspace that gets extremely cold (i.e. freezing) in the winter.

I'm going to use a drainable ball-valve inside the house so I can drain it in the winter but how can I run the pex line to make sure it's sloped? The run is about 25 feet long.

I think I have two options:

1) Run it through floor joists (requires a hole in every joist since my line is running perpendicular to them)

2) Run it under the joists and use clamps and wood shims under each joist to achieve a slope.

I'm leaning towards #1 but to make sure I have a good slope I think I'll need to measure my holes to make sure the line is actually sloping. For example, I thought I would measure a certain distance from the joist to the floor above to make sure my holes are actually sloping down.

Any other suggestions?

(NOTE: This question is sort-of a follow-up to this: Do I need to angle/pitch pex tubing for draining in the winter?)


  • 1
    another suggestion: add a valve to allow you to blow it out.
    – Steven
    May 11 '16 at 16:35

If you have an air compressor you can plumb in a connector for an air line after the shuttoff valve for the line.

Then leave the faucet open at the end of the line and connect the air compressor with a pressurized tank. This will blow out the line and prevent freezing.

Good luck!

  • Thanks! Is there Sharkbite fitting I can use for this or something else? Also, how powerful of an air compressor do I need? (I suppose this is a good reason to buy one!)
    – SofaKng
    May 12 '16 at 2:14
  • Also, if I plan on doing this then do I even need to worry about the slope of the line or anything else freezing?
    – SofaKng
    May 12 '16 at 2:23
  • If you use air to blow the line you can ignore the slope since you won't be using gravity to drain it. A 2-3 gallon nailer compressor works just fine. A small tire inflating compressor doesn't. You have to create your own fitting and isolation valve for the air compressor input.
    – ArchonOSX
    May 12 '16 at 16:33

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