T&P options in a crawl space

[Doug Henningsen]

This electric heat pump water heater is installed in a crawlspace (6" ceiling). The water heater is sitting on a reinforced 4" concrete pad. The crawl space floor is crushed rock except for the WH pad. Would it be acceptable to allow the T&P valve to simply dump into the crushed rock in the crawl space? Could the same be done with the condensate line?

Two alternatives:

1. Pipe the T&P and condensate lines to a sump with a float to pump outside. (Probably the appropriate approach but rather difficult given rocky soil condition and distance.)

2. The house's main sewer line is right next to the water heater but about 28" above the base of the water heater (ie not a floor drain). A "P" Trap could be installed about 10" under the T&P. (Probably not permitted because it is above floor height?)

Thanks

Doug

 

[Dana]

There may be local code issues limiting your options. Dumping it on the ground might work, but might not. If it's a vented crawlspace with a concrete foundation wall surrounding it it's going to retain more moisture than if it's a pier & beam foundation with skirting.

Option 1 is probably a NO for the T & P valve, but fine for the condensate. A sufficiently big sump pump would be able to keep up with the flow volume of an open T & P valve, but would need to be rated for operating at the T & P valve's high temp limit. I'm sure there are sump pumps that can handle those temps, but they're not the inexpensive sump pumps you're likely to find at the local box store.

Option 2 is almost certainly going to fail plumbing codes. For a P-trap in a drain to function it has to have water in it- in the ideal world the T & P valve would never open, ergo no water in the P-trap. I doubt hard-plumbing the T & P output into the sewer line would cut it code-wise either.

Plumbing the T & P output to the outdoors into a small dry well or catch basin probably works, but it can't simply be daylighted on the surface without creating a scalding risk.

 

[Sponsor]

 

[wwhitney]

The 2016 California Plumbing Code has this to say about the discharge piping for a T&P valve:

608.5(3) Discharge pipe shall discharge independently by gravity through an air gap into the drainage system or outside of the building with the end of the pipe not exceeding 2 feet (610 mm) and not less than 6 inches (152 mm) above the ground and pointing downwards

Cheers, Wayne

 

[Doug Henningsen]

Dana and Wayne,
Thanks for your insight and advice. There is a perimeter foundation and the crawl is very much UNsealed. Once I read your comments I re-examined the alternatives and found a shorter route and gravity (not a pump) would work. Unfortunately, I will have to bore through the foundation and it will dump water at the corner of the carport (next to a downspout) where the drive slope will move the water away from the house/foundation. It naturally is noticeable and since it doesn't freeze here, this might be the best option. And, since T&P discharges should be rare, it won't be noticeable.

Would you still put a drain (air gap) at the base of water heater or could I plumb it direct (no air gap) to the outside? Now I'm asking partly out of curiosity...as you mentioned, I really need the city on board (beyond the approved permit) before boring through my foundation.
Thanks again,
Doug

 

[wwhitney]

The air gap is just if you dump it in the sanitary sewer. If you take it outside, the air gap is the 6" - 24" between the outlet and the ground.

Cheers, Wayne