Where are you located? And could you post the source and the code?

I'm not doubting you be requiring indirect connection in the same room as the water heater seems to be an undue burden on the home owner. To make it "maintenance free" the homeowner would also have to run a trap primer. Again, this seems to be a burden to anyone in the area of concern. Also, I believe having the T&P discharge outside would be safer. A T&P that trips as intended could be dangerous if anyone was there at the time.

Sorry, not an answer to your question, my curiousity is peaked.

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Florida Plumbing Designer