Can you use copper flex pipping for the TPRV drain line. It extends down for about a foot connects to regular copper pipping and then out to the exterior.
First time I have seen this.
I personaly would not have a problem.
If it’s 3/4" and not kinked I would have no problem with it.
See the TPR mini course here in the NACHI site.
Technically, the answer is No, you should not use the common flexible water supply connector such as a BrassCraft BD00 but you do see it quite often. As an example, a typical Cash Acme T&P valve will discharge at a pressure of 175 psi and/or a temperature of 210°F. The BrassCraft flexible copper connector is rated at 125 psi at 180°. So, you can easily see where the water being discharged could exceed the operating characteristics of the flex connector. The argument, although weak, is that the temperature and/or pressure would only be present for a short period of time. Well, that’s the rub isn’t it? How long is too long? 1 second, 10 seconds, a minute? I admit that it does make for a nice looking installation but I’m of the opinion that it is not proper.
Here’s a snippet from the BrassCraft catalog re: copper flex connectors:
The pressure you speak of does not account for the fact there is flow.
If it was flex on its own I would be more concerned with movement of the pipe.
175 is the pressure if capped
Describe exactly what you mean by flex. Are you talking soft copper or other and how is it connected to the hard copper?
In my neck of the woods, the answer is no. I had it confirmed a few weeks ago by a local AHJ and two plumbers.
Not allowed by the CPC (UPC). Not now, not ever 
Jeff, do mean soft copper or corrugated flex?
Can you post the relevant portion of the CPC(UPC)
I’ll take marketing for $500 Russel…
Buzz, Buzz…
RR, “Yes, Rick”
What is, When do you you want your phone to ring?
:mrgreen: 
:mrgreen:
ROTFLMAO. My VRS made one of its few errors, inserting “know” for “no.” I manually went and corrected it by deleting that stupid K. I didn’t realize that W’s could be so problematic.
Corrected my previous post. Thanks, Jeff.
I just got in from a rough 7:00 a.m. inspection, so I needed this humor! 
608.5 Relief valves located inside a building shall be provided with a drain, not smaller than the relief valve outlet, of galvanized steel, hard drawn copper piping and fittings, CPVC, or listed relief valve drain tube with fittings which will not reduce the internal bore of the pipe or tubing (straight lengths as opposed to coils) and shall extend from the valve to the outside of the building with the end of the pipe not more than two (2) feet (610 mm) nor less than six (6) inches (152 mm) above the ground or the flood level of the area receiving the discharge and pointing downward. Such drains may terminate at other approved locations. No part of such drain pipe shall be trapped or subject to freezing. The terminal end of the drain pipe shall not be threaded.