TPR drain grey area

[Marc M]

Jerry,
House is 2001
Reference: 2003 IRC

Both state that the TPR drain line material must be of a similar material as that of the interior plumbing materials excluding pvc.
IRC2803.6.1 including T605.5

My question is this;
they state what mateials CAN be use, but they do not say that that flexible copper mateial ( seen on water heater supply) is NOT acceptable. The installation from the TPR to the fitting placed in the wall is only 24" or so. So is it safe to say that so long as the TPR drain is not reduced less than the TPR drain, and no more than 4 - 90's are used it's okay?

[Jerry Peck - Codeman]

Hi Marc,

Now you've gone and done it ... you've asked a simple compound question with a complex answer.

First, I will address this part:
"Both state that the TPR drain line material must be of a similar material as that of the interior plumbing materials excluding pvc."

It does not really say "excluding PVC", it just states "P2803.6.2 Relief valve drains. Relief valve drains shall
comply with Section P2904.5 or ASME A112.4.1.", and P2904.5 is Table P2904.5, Water Distribution Pipe, which does not list PVC as suitable for water distribution pipe inside a house as PVC does not have the appropriate pressure rating at a high enough temperature rating to be used for hot water. On the other hand, PVC is allowed for use outdoors as the water service pipe in Table P2904.3, Water Service Pipe, as water service pipe is cold water only.

Thus, PVC is excluded by not being included.

You next part of the question is about using copper for the T&P relief valve discharge drain line, and, yes, copper is allowed for that use ... only you specifically asked about flexible copper, as in those flexible copper connectors.

First, being as you reference the 2003 IRC, let us first review P2803.6.1 Requirements of discharge pipe. (underlining and bold are mine)
- P2803.6.1Requirements of discharge pipe. The outlet of a pressure relief valve, temperature relief valve or combination thereof, shall not be directly connected to the drainage system. The discharge from the relief valve shall be piped full size separately to the floor, to the outside of the building or to an indirect waste receptor located inside the building. In areas subject to freezing, the relief valve shall discharge through an air gap into an indirect waste receptor located within a heated space, or by other approved means. The discharge shall be installed in a manner that does not cause personal injury or property damage and that is readily observable by the building occupants. The discharge from a relief valve shall not be trapped. The diameter of the discharge piping shall not be less than the diameter of the relief valve outlet. The discharge pipe shall be installed so as to drain by gravity flow and shall terminate atmospherically not more than 6 inches (152 mm) above the floor. The outlet end of the discharge pipe shall not have a valve installed.

Okay, what is "In areas subject to freezing" and how do we define that?

We start by referring to Appendix D in the IPC and Degree Day and Design Temperatures, using the Winter 97-1/2% Design Temperature and go down to each location where the temperature is below 32 degrees. Take all those points and connect them together and that is what I refer to as "the freeze line", which is basically approximately along Interstate 10 across North Florida, up through lower Texas, to California. In California, that would include areas south of Fresno (shown as 30 degree design temperature) and south of Sacramento (shown as 32 degrees).

In California, I-10 is approximately 200 miles south of Fresno, which is about 160 miles south of Sacramento, so I-10 does not work well for the freeze line in California, but it does from Florida through Texas.

I digressed some, but if Appendix D shows a Design Temperature of less than 32 degrees then it is reasonable to presume that the area is "subject to freezing". And, if "subject to freezing", then the termination point is required to be inside, through an air gap, in the heated space, which further implies that the water heater is not to be located outside that same heated space.

Doing this with those flexible copper connectors would not be a wise thing as those are, well, flexible, and the discharge line needs to be securely held in place.

However, if the flexible copper connector went from the T&P relief valve outlet to a secured pipe of a suitable material which was securely and firmly secured in place, then the flexible copper connector should work and be acceptable ... as long as those connectors meet (are labeled as meeting) ASTM B 42, ASTM B 302, ASTM B 75, ASTM B 88, ASTM B 251 or ASTM B 447 ... or are specifically labeled as being suitable for use as a T&P relief valve discharge piping material. I have not looked to see if they are labeled as meeting one of those ASTM standards or are otherwise specifically labeled as being suitable for that use.

Next time you see one installed, check the ASTM standard to which it is labeled, let me know if it meets one of the ASTM standards listed or is otherwise labeled as being specifically suitable for that use. Thanks.

I should add, though, that those "flexible" copper connectors are not what I would call "flexible" ... "bendable" would be a more appropriate term to use, and when they are "bent" (versus being "flexed") they tend to deform, and that deformation tends to flatten the shape out, which thereby creates a "reduction in size", which is not allowed for T&P discharge lines.

[Marc M]

Wow...I can see the light. Thanks a bunch.