I was wondering if the pressure relief valve can be vented right under the house or does it have to be ran to the outside of the house. Also is there another method such as a catch pan that I can employ? I live in Washington.
Most codes state that it must be vented to the outside.Check with your city code enforcer or county office.
it should be run outside but most people don,t even use one. you can get a catch pan that fits under the heater but you,ll have to raise your heater up to install it.
I would be curious to see what plumbing professionals have to say about this. From what I could find, the codes for water heater relief valves just say that the valve must have a drain pipe that discharges the hot water and steam down low, instead of up near the top where it can spray in your face. They also say that the discharge should be outside of the building, but that this is not always feasible and you can install a drip pan below the water heater for this purpose. In this case, I would think that running the discharge line to underneath the house should be okay. But, I'm not a plumber. For what it's worth, my water heater is in a closet that's accessed from outside and the discharge line from my pressure relief valve just discharges to the bottom of the closet (this was installed by a licensed plumber and signed off by the city on a remodel 2 years ago). Apparently, it's okay to just let the discharged water flow out from underneath the water heater closet door to the outside. So, I don't see why it would be against code to run the discharge line to a crawl space under the house. The point of the codes is to prevent your water heater from exploding and destroying your house (or killing or injuring you).
