We're gonna have a blast!

 The photo below has got to be one of the most misunderstood safety devices in all of plumbing. Safety devices in plumbing? What could be the big deal, you ask. After all, as one plumber explained to me once: Plumbing is pretty easy, if you put water in a pipe it runs downhill.  That theory is not bad for drains at least. The logical question is, so what is the safety issue? There are some more subtle safety concerns, like air-gaps on dishwashers, back flow prevention devices to keep gray water out of the potable water. But the main safety device home inspectors look at is the water heater temperature pressure relief valve and the drain from it. I would say that about 30 percent of the time, the drain line is defective. Usually it is routed up. But sometimes it is the wrong material, like PVC or a garden hose serving hot water. Other times there is no drain line so a discharge would be directed into a room or straight out. People, who know no better, will argue that it does not matter if it goes up -- steam will be discharged in an emergency. The problem there is that, periodically, these devices might operate to relieve instances of high water pressure, but not extreme emergency situations. If the system is correctly plumbed that is a very rare occurrence, but if it is a closed system with no expansion tank, the TPR might drain during times when lots of hot water is being produced. And when that happens, we are not talking about big bursts of steam, just a half a cup or so of water running out. Obviously, if this is seen, the  problem in the basic system should be addressed as well. So, if the drain runs up, this quantity of water that is basically routed by gravity -- no fireworks -- stays in the pipe down by the TPR valve. Over time, that can damage the valve mechanism so, when the big one comes -- it is locked shut. Hold on to your hat, and whatever else you have that might be loose. This is gonna be a real blast! Check out the video link. 

Thanks for looking.

Steven L. Smith

www.kingofthehouse.com

Bellingham, wa. home inspector