Laundry room water heater
What's wrong here?
- The relief discharge drops to the floor and then climbs to the tub, so it is trapped and does not drain by gravity
- A relief valve may not discharge into a laundry tub
- An electric water heater does not need a temperature and pressure relief valve
- The heater must sit in a drain pan because it is in a laundry room
Show the answer and the code reference
The answer
The T&P discharge pipe is trapped: it drops to the floor, runs level, then climbs about 3 ft to get over the laundry tub rim.
Correct choice: 1. The relief discharge drops to the floor and then climbs to the tub, so it is trapped and does not drain by gravity
UPC 608.5 requires relief valve discharge piping to discharge independently by gravity, and no part of it may be trapped. This pipe holds standing water in the low run along the floor, and when the valve opens, scalding water and steam have to push that column uphill before anything reaches the tub. Trapped discharge lines also collect scale and corrosion, which can restrict or plug the pipe, and the standing water can back up against the valve seat. Nothing found suggests Minnesota's amendment to 608.5 drops the no-trap rule.
How to fix it
Rerun the discharge so it falls continuously from the valve outlet to its end. The valve outlet is higher than the tub rim, so the pipe can run from the valve with a steady downward pitch over to the tub and end pointing down above the rim; or drop it straight down the side of the heater to a floor drain or other receptor through an air gap.
Code references
UPC 2018 608.5 — Discharge Piping
Relief valve discharge piping must be at least the size of the valve outlet, have no valves or obstructions, discharge full size and pointing down, and discharge independently by gravity through an air gap into the drainage system or outside the building. No part of the discharge pipe shall be trapped or subject to freezing, and the terminal end shall not be threaded.
Drills citing 608.5UPC 2018 608.3 — Expansion Tanks, and Combination Temperature and Pressure-Relief Valves
Storage water heating equipment shall be provided with an approved, listed, adequately sized combination temperature and pressure relief valve, installed in an approved location per the manufacturer's instructions.
Drills citing 608.3
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 results indicate Minn. Rules 4714.0608 amends UPC 608.5, reportedly letting the discharge end at a safe place of disposal or within 18 in. of the floor. The amended text could not be read for this drill. The no-trap rule this drill turns on is in the model 608.5, and nothing found suggests Minnesota dropped it.
About the Minnesota Plumbing CodeCitation under review. Minn. Rules 4714.0608 could not be read (revisor.mn.gov blocked; search snippets only). Confirm that the amended 608.5 keeps 'No part of such discharge pipe shall be trapped' and the gravity-discharge wording, and record the actual termination wording (reported as 'a safe place of disposal or within 18 inches of the floor').
Why the other choices are wrong
- A relief valve may not discharge into a laundry tub. 608.5 allows the discharge to go into the drainage system through an air gap, and a laundry tub with the pipe ending above its rim is a common, accepted receptor. The tub is fine; the route to it is the problem.
- An electric water heater does not need a temperature and pressure relief valve. UPC 608.3 requires a listed combination temperature and pressure relief valve on storage water heating equipment, gas or electric. Electric elements can overheat a tank too when a thermostat sticks.
- The heater must sit in a drain pan because it is in a laundry room. UPC 507.5 requires a pan where a leak would damage the building: attics and floor-ceiling or floor-subfloor assemblies. This heater sits on a basement slab, where a pan is not required.