Improper TPR piping

I was in the process of writing up the TPR drain line when I noticed an installation manual sitting next to the water heater. I always flip through these when I find them. Anyway, I noticed the manufacturer’s recommendation was that no more than FOUR elbows be installed in the line. As you can see, there are four in the pic, plus two more in the wall. There is no mention of this in the IRC that I could find.

Even a drain line installed properly to flow to gravity may have an excessive number of elbows, although I’ve never seen it. Just thought I’d pass this along.

You did write it up though, right? The uphill drain line is a no no. . .

Although the number of bends is not directly limited by the IRC, it does require equipment to be installed per the manufacturers instructions … so it would be a requirement for that water heater.

The TPRV piping is also suppose to flow downward, and have an open and visible termination … both of which may be an issue with that WH.

Jeff and Mr. O, Oh yeah, I wrote it up. I just wanted to let people know that an excessive number of elbows may be an issue as well.

I always look for an excessive number of elbows and have a special paragraph for that condition.

I would also be concerned about the steel pipe, it should not terminate with any threads to avoid a cap being screwed on. appears to be galvanized but rust could still occur.

DSG Home Inspection Services of NH

(also lic Master plumber)

good call. if the installer didn’t know enough not to have it run uphill, then he likely didn’t cut the theads of the other end of the last pipe in the “system”.

ok…is there not a galvonic reaction issue here as well…with the copper ( sloppy A$$ work anyway ) to the galvonized piping…?

Yeah…Yeah…I know…Shut Up Electrician…but I figured I would ask…:slight_smile:

Hi Paul
Since there’s no water present in the TPR line (or at least there shouldn’t be) I don’t think the dissimilar materials would cause a problem.


The item which prevents galvanic corrosion when dissimilar metals are used is called a “dilectric union”

At the least a brass fitting between the (2) metals should be enough to remove it issue…man I forgot water actually had to be present to cause the reaction…because it acts like an Electrolyte and speeds up the process.

But alas…you are correct as the water in a pipe actually essentially going on is that the liquid inside the fittings is acting as an electrolyte of a battery - If the electrolyte can’t conduct a significant number of electrons (be a good electrolyte) it won’t promote corrosion.

Great info…Nice

So where did the moisture come from to make the vertical copper streak green as it is? Like a copper penny in the rain for a few weeks. Or do we call this Pitinaed Copper. ha. ha.

Paul, good catch on the dieelectric fitting, I saw that too, but you were one step ahead of me. Not bad for an electrian. ha. ha.



There should be seven elbows in your picture.

The four you see,
One turning down in the wall.
One turning toward the outside wall,
One turning down at the termination point.

Most instructions I’ve seen call for no more than four elbows. I always write it up whether they change it or not.

AO SMITH Instructions:

The temperature-pressure relief valve must be installed directly into
the fitting of the water heater designed for the relief valve. Position the
valve downward and provide tubing so that any discharge will exit
only within 6 inches (153 mm) above, or at any distance below the
structural floor. Be certain that no contact is made with any live electrical
part. The discharge opening must not be blocked or reduced in size
under any circumstances. Excessive length, over 30 feet (9.14 m), or
use of more than four elbows can cause restriction and reduce the
discharge capacity of the valve.

I wouldn’t be as concerned with Diel. reaction since you lack water flow, if you had water flow that would be a BIGGER problem. In many cases, (as a plumber) it is nice to see the termination in the same room as the water heater, that way any problem is found immediatly. some garden condos like to tie several together and terminate once , then you don’t know which one has the problem. If this was in an outside shed with freezing potential, a small ampont of water in the trapped drain could freeze making the TPR useless.