Spot the Violation

PlumbingWater supply & distributionLevel 22018 UPC

Crawlspace water lines

Inside a crawlspace, looking toward the concrete block foundation wall. 2x10 floor joists at 16 in. on center run overhead toward the wall, and a poly vapor retarder covers the ground. Two 3/4 in. PEX lines run side to side across the frame just below the joists, parallel to the wall: the hot line in gray foam pipe insulation above a bare blue cold line. Gray plastic two-pipe hangers are nailed to the sides of two joists, one left and one right of center, with three joists between them that carry no hanger; between the hangers the lines droop in a long, low curve, and beyond them they droop again toward the edges of the frame. An aluminum clamp work light hangs from a joist at the upper left.
Crawlspace under a one-story addition, new water distribution

What's wrong here?

  1. The PEX hangers are about 64 in. apart, twice the 32 in. maximum, and the lines sag between them
  2. Hot and cold PEX may not share a hanger
  3. PEX may not run below the joists; it has to be bored through them
  4. Nothing. This installation is compliant
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Show the answer and the code reference

The answer

The 3/4 in. PEX is hung only at every fourth joist, roughly 64 in. between supports, and it sags in between. PEX 1 in. and smaller must be supported at least every 32 in. when it runs horizontally.

Correct choice: 1. The PEX hangers are about 64 in. apart, twice the 32 in. maximum, and the lines sag between them

UPC 313.3 requires suspended piping to be supported at intervals no greater than Table 313.3, and the table limits horizontal PEX 1 in. and smaller to 32 in. between supports (larger PEX gets 4 ft). With joists at 16 in. on center, a hanger every second joist meets the limit; here there are three bare joists between hangers. PEX softens and grows when it carries hot water, so long spans droop, put stress on the fittings and look like what they are at inspection. Many PEX makers ask for the same or closer spacing, and their instructions apply too.

How to fix it

Add a hanger at every second joist (32 in.) or closer, so each span is no more than 32 in. Continuous PEX support channel is another way to stretch the spacing if the PEX maker allows it.

Code reference

  • UPC 2018 313.3 — Suspended Piping

    Suspended piping is to be supported at intervals not exceeding those shown in Table 313.3. For PEX, the table gives 32 in. horizontally for 1 in. and smaller and 4 ft for 1-1/4 in. and larger, with vertical support at the base and each floor and mid-story guides.

    Drills citing 313.3

Minnesota

MN status unverifiedConfidence: medium

Minnesota adopts the 2018 Uniform Plumbing Code with Minnesota amendments as the Minnesota Plumbing Code (Minn. Rules ch. 4714, effective Dec. 17, 2021). Search-result snippets show Minn. Rules 4714.0313 restating Table 313.3 with the same PEX row as the model code (32 in. horizontal for 1 in. and smaller, 4 ft for 1-1/4 in. and larger), so the spacing this drill turns on appears unchanged. What Minnesota changed elsewhere in the table could not be confirmed; check ch. 4714 before relying on other rows.

About the Minnesota Plumbing Code

Why the other choices are wrong

  • Hot and cold PEX may not share a hanger. No UPC rule bars a two-pipe hanger. Separation between hot and cold lines is an efficiency choice, not a support requirement.
  • PEX may not run below the joists; it has to be bored through them. Running below the joists is allowed. The lines just have to be supported at the Table 313.3 spacing and kept out of harm's way.
  • Nothing. This installation is compliant. About 5 ft between supports might pass for small copper tube, but Table 313.3 holds PEX 1 in. and smaller to 32 in. horizontally, and the sag shows why.
Code complianceLevel 2 · Journeyman#PEX#supports#hangers#spacing#crawlspace#Table 313.3

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