Spot the Violation

PlumbingWater heatersLevel 12018 UPC

Gas water heater by the floor drain

Unfinished basement with a concrete block wall. A 40-gallon gas water heater stands on the slab with a draft hood and vent pipe on top and copper hot and cold lines rising to the joists, the cold line with a ball valve. A black iron gas line drops at the left with a yellow-handled gas cock and a capped drip leg before the gas control. On the right side of the tank a brass relief valve feeds a copper pipe that runs straight down the side of the tank, through a brass ball valve with a red lever, and ends a few inches above a round floor drain in the slab. The edge of a furnace and its supply duct are at the left.
Basement water heater, new installation

What's wrong here?

  1. A shutoff valve is installed in the relief valve discharge pipe
  2. The relief valve discharge must be piped through the wall to the outdoors
  3. The gas line needs a sediment trap ahead of the gas control
  4. A ball valve is not allowed on the cold water inlet to a water heater
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Show the answer and the code reference

The answer

Someone put a ball valve in the T&P relief discharge pipe. If it gets closed, the relief valve has nowhere to discharge and can't protect the tank.

Correct choice: 1. A shutoff valve is installed in the relief valve discharge pipe

The temperature and pressure relief valve is the last thing between an overheated, over-pressured tank and a tank explosion. UPC 608.5 says the discharge piping serving a relief valve shall have no valves, obstructions or means of isolation, because a valve that is shut (by a homeowner tired of a dripping T&P, or by a tech who never reopens it) blocks the relief valve as surely as a plug. Nothing found suggests Minnesota's amendment to 608.5 drops that rule. The rest of this discharge is fine: full-size copper, running straight down, unthreaded, ending a few inches above the floor drain.

How to fix it

Cut out the ball valve and replace it with a straight piece of 3/4 in. copper so the discharge runs full size and open from the relief valve outlet to its end above the floor drain. If the relief valve is dripping, find out why (high pressure, thermal expansion, a bad valve) instead of valving it off.

Code references

  • UPC 2018 608.5 — Discharge Piping

    Discharge piping serving a temperature relief valve, pressure relief valve or combination valve shall have no valves, obstructions or means of isolation. It must be at least the size of the valve outlet, discharge independently by gravity through an air gap into the drainage system or outside the building, not be trapped or subject to freezing, and its terminal end shall not be threaded.

    Drills citing 608.5

  • UPC 2018 606.5 — Control Valve

    A control valve shall be installed immediately ahead of each water-supplied appliance and immediately ahead of each slip-joint or appliance supply. For a water heater, that is the shutoff on its cold water supply.

    Drills citing 606.5

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 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 instead of the model code's drainage-system-or-outdoors wording. The amended text could not be read for this drill. The no-valve rule this drill turns on is in the model 608.5, and nothing found suggests Minnesota dropped it.

About the Minnesota Plumbing Code

Citation under review. Minn. Rules 4714.0608 could not be read (revisor.mn.gov blocked; search snippets only). Confirm: (a) the amended 608.5 keeps 'no valves, obstructions, or means of isolation'; (b) the termination wording (reported as 'a safe place of disposal or within 18 inches of the floor'); (c) one snippet mentioned a check valve and fullway shutoff 'within the discharge line' in 4714.0608; confirm that belongs to some other discharge (for example a pump or relief discharge to a sewer) and not to T&P discharge piping, or this drill's answer would need rework. UPC 2018 606.5 now cited with its actual control-valve wording, which covers the water heater as a water-supplied appliance.

Why the other choices are wrong

  • The relief valve discharge must be piped through the wall to the outdoors. UPC 608.5 lets the discharge go into the drainage system through an air gap, and this one ends a few inches above a floor drain. Minnesota's amendment to 608.5 is reported to allow ending within 18 in. of the floor as well. A pipe run out through a Minnesota rim joist would also risk freezing, and 608.5 forbids discharge piping subject to freezing.
  • The gas line needs a sediment trap ahead of the gas control. It has one: the capped nipple below the tee at the bottom of the gas drop is the drip leg (sediment trap) the fuel gas code asks for.
  • A ball valve is not allowed on the cold water inlet to a water heater. The opposite is true. UPC 606.5 requires a control valve immediately ahead of each water-supplied appliance, and a water heater is one, so the cold inlet needs a shutoff. Only the relief discharge line must be free of valves.
Safety hazardLevel 1 · Apprentice#T&P#relief valve#discharge pipe#ball valve#basement#gas water heater

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