Water Heater air gap, below T&P valve

[mm]

Does there really have to be a full 6" gap betwen the bottom of the T&P discharge pipe and the floor?

I don't see the purpose of it.

The instructions that came with the water heater say to leave a 6" air gap between the temperature and pressure pipe and the floor drain. The water heater that was first installed in the house was like that too.

I have a pan under the WH and if the discharge pipe came to within an inch or two of the pan, I think more of the water would go into the pan when I lifted the T&P lever. And less on the floor.

[Don Young]

Be aware that, if the T&P valve should ever be called on to do what it is intended to do, what comes out of the pipe is a tremendous blast of boiling water and steam. Whether it goes into the pan first or directly on the floor would not matter much. The six inches is intended to ensure that the heater be vented as rapidly and safely as possible, and also to minimize any possibility that the water in the heater could ever be contaminated by drain or ground water. I agree that it is nice to understand the reasons for code requirements, but if you do not understand the reason that is all the more reason to comply since there is obviously something you haven't thought of. Codes are primarily for safety, after all.

Don Young

[michaelcherr]

michaelcherr had written this in response to

: Not entireley code based, but the Rental Registry inspection in my area mandated that the T&P discharge terminate within 6" of the floor. (ie 6" or less) most everything else I read states 6" without saying whether that is a min or max.

I do disagree slightly with Don's assertion that water will come rushing out. While this can and does happen, the T&P valves I've seen having water come out, it's only been a trickle.

Mike

D>> Does there really have to be a full 6" gap betwen the bottom

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[RickMeister]

If a T&P blows due to burner or T-stat malfunction, you'll see hot water and steam bursting out of that pipe. That's why they want it terminating close to the floor--so no one gets scalded. But they don't want it touching the floor in case the heat goes out and it's freezing in the house. They don't want ice blocking the flow.