4 pipes coming from water heater?

[emo7874]

I'm trying to figure out what a 4th pipe is for coming out of my water heater.

There's a cold in, hot out, T&P coming out of center top of tank. The 4th branches off the cold in and runs outside the garage and is open ended. Is that another T&P?

 

[phishfood]

That sounds like a thermal expansion relief line. Is there a brass valve in that line?

 

[emo7874]

Yes, there is a small brass connection labeled "regulator" that connects to PVC leading outside the garage. My main question is does it really have to run outside the garage. Can I run it to the same place as the T&P pipe?

 

[phishfood]

The thermal expansion valve is designed to release pressure buildup when the cold water entering the water heater is heated and therefore expands. It will operate on a regular basis, releasing small amounts of water every time. Therefore, unless the line that is attached to the T&P valve is routed to a location that won't be a nuisance or otherwise cause problems, I wouldn't.

Another option is to install an expansion tank in place of the expansion valve. This is a small bladder tank that absorbs the increasing volume of the expanding water, and therefore does not release water every time.