Upstairs laundry room water heater
What's wrong here?
- The water heater sits directly on the finished floor with no drain pan under it
- The relief valve should discharge into a drain pan under the heater instead of a standpipe
- A relief valve may not discharge into an indirect waste receptor such as a funnel standpipe
- The water heater has to be raised at least 18 in. off the floor
Show the answer and the code reference
The answer
There's no drain pan. The heater sits right on a second-floor floor-subfloor assembly, where a leak will run through into the rooms below.
Correct choice: 1. The water heater sits directly on the finished floor with no drain pan under it
Every tank eventually leaks, and on an upper floor the water goes straight into the subfloor, the ceiling below and the walls. UPC 507.5 requires a watertight, corrosion-resistant pan under a water heater installed in an attic or in or on an attic-ceiling, floor-ceiling or floor-subfloor assembly where a leak would cause damage, with a drain of at least 3/4 in. to an approved location, and the pan must be at least 1-1/2 in. deep. The relief valve discharge here is acceptable: full-size copper ending with an air gap over a funnel receptor. UPC 608.5 also bars discharging the relief valve into the pan once one is installed.
How to fix it
Drain the heater, set it in a listed water heater pan sized for its base, and run the pan's 3/4 in. (or larger) drain to an approved location: an indirect receptor through an air gap, or another location the inspector approves. Keep the T&P discharge separate from the pan drain.
Code references
UPC 2018 507.5 — Drainage Pan
Where a water heater is in an attic, or in or on an attic-ceiling, floor-ceiling or floor-subfloor assembly where a leak would cause damage, a watertight pan of corrosion-resistant material shall be installed beneath it with a drain of not less than 3/4 in. diameter to an approved location. The pan shall be not less than 1-1/2 in. deep.
Drills citing 507.5UPC 2018 608.5 — Discharge Piping
Relief valve discharge piping discharges full size, by gravity, through an air gap into the drainage system or outside the building, with no valves, traps or threaded end. Discharge from a relief valve into a water heater pan is prohibited.
Drills citing 608.5
Minnesota
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 suggest Minn. Rules 4714.0507 amends UPC 507.5 but keeps the watertight, corrosion-resistant pan with a 3/4 in. drain for heaters in attics and on floor-ceiling or floor-subfloor assemblies, and repeats that a relief valve may not discharge into the pan. The amended text could not be read, and whether the 1-1/2 in. pan depth survives was not confirmed.
About the Minnesota Plumbing CodeCitation under review. Minn. Rules 4714.0507 could not be read (revisor.mn.gov blocked; search snippets only). Confirm that the Minnesota version of 507.5 still requires a pan under a water heater on a floor-subfloor assembly where a leak would cause damage, and whether the 1-1/2 in. depth survives. Also confirm that the 'no relief valve discharge into a water heater pan' sentence is item (7) of UPC 2018 608.5 (cited here from memory of the 2015/2018 list; the snippets also put a version of it in Minnesota's 507.5).
Why the other choices are wrong
- The relief valve should discharge into a drain pan under the heater instead of a standpipe. UPC 608.5 prohibits discharging a relief valve into a water heater pan. The pan catches tank leaks; the T&P gets its own full-size discharge to an approved place.
- A relief valve may not discharge into an indirect waste receptor such as a funnel standpipe. UPC 608.5 lets the relief discharge go into the drainage system through an air gap. The pipe ends above the funnel with a visible air gap, so this receptor is fine.
- The water heater has to be raised at least 18 in. off the floor. The 18 in. rule (UPC 507.13) is for the burners and ignition devices of fuel-burning appliances in garages, where gasoline vapor collects near the floor. This is an electric heater in a laundry room.