Spot the Violation

PlumbingFixtures & clearancesLevel 12018 UPC

Basement bath rough-in

Corner of an unfinished basement bathroom at rough-in. Two framed 2x4 walls stand in front of blue foam board on the foundation. A white 3 in. PVC closet flange is set in the concrete slab near the left-hand wall, with a copper supply stub coming out of the back wall beside it. A yellow tape measure lies on the slab, hooked on the left wall's bottom plate and run across the flange, reading 11 at the flange center. Farther right, a capped 1-1/2 in. drain stub and red and blue PEX stubs serve a future lavatory. 12345678910111213141516171819202122
Basement bathroom, rough-in inspection

What's wrong here?

  1. The closet flange is centered only 11 in. from the side wall; a water closet needs at least 15 in. from its center to a side wall
  2. The closet flange must be at least 15 in. from the back wall
  3. The water closet supply must come up out of the floor, not the wall
  4. Nothing. This installation is compliant
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Show the answer and the code reference

The answer

The toilet flange is set 11 in. from the side-wall framing to its center, short of the 15 in. minimum from a water closet's center to a side wall.

Correct choice: 1. The closet flange is centered only 11 in. from the side wall; a water closet needs at least 15 in. from its center to a side wall

UPC 402.5 says no water closet may be set closer than 15 in. from its center to a side wall or obstruction, and it requires at least 24 in. of clear space in front of it. The flange position fixes where the bowl goes, so this is the time to catch it: once the slab is patched and the walls are hung, 1/2 in. drywall and tile will bring the finished wall to about 10-1/2 in. from center. A bowl that close leaves no room to sit squarely, to clean, or to reach the paper holder, which is why inspectors measure the flange at rough-in.

How to fix it

Break out the slab and move the flange so its center is at least 15 in. from the finished face of the side wall (lay it out at 15-1/2 to 16 in. from the studs to allow for drywall and tile), keeping the bowl's rough-in distance from the back wall. Re-test the drain before the slab is patched.

Code reference

  • UPC 2018 402.5 — Setting

    Fixtures must be set level and in proper alignment. No water closet or bidet may be set closer than 15 in. from its center to a side wall or obstruction, nor closer than 30 in. center to center to a similar fixture, and the clear space in front of a water closet, lavatory or bidet must be at least 24 in.

    Drills citing 402.5

Minnesota

MN adopts this rule as writtenConfidence: medium

Minnesota adopts the 2018 Uniform Plumbing Code with Minnesota amendments as the Minnesota Plumbing Code (Minn. Rules ch. 4714, effective Dec. 17, 2021). No Minnesota amendment to UPC 402.5 is known; check ch. 4714 before relying on it.

About the Minnesota Plumbing Code

Why the other choices are wrong

  • The closet flange must be at least 15 in. from the back wall. The distance to the back wall is the toilet's rough-in dimension (usually 12 in.), set by the bowl the owner buys; the 15 in. rule in 402.5 is measured to a side wall or obstruction.
  • The water closet supply must come up out of the floor, not the wall. Toilet supplies are normally stubbed out of the wall a few inches left of center; nothing in the code requires a floor supply.
  • Nothing. This installation is compliant. The tape reads 11 in. from the framing to the flange center, and the finished wall will bring the wall even closer, well under the 15 in. minimum.
Code complianceLevel 1 · Apprentice#water closet#toilet#clearance#closet flange#rough-in#basement

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