During a local ASHI chapter meeting the question came up about using copper flex line at the water heater TPR valve. Is the use approved or NOT. The flex connection is typically used when a handyman or home owner replaces a water heater.

The copper flex tubing makes it much easier to install than the solid copper tubing and during replacement the old TPR discharge line never matches up to the new one. That's not to say I haven't been seeing this installed on original installations, because I have.

And because I've seen it time and again installed in brand new homes I figured that this was an accepted method and approved by the local building department. Go for a ride with me on the internet - look up the requirements for the discharge line at your local building department website and you'll find what I found. Either a reference to the ANSI/ASME studies, manufacturer's installation instructions or the requirement for a 3/4 inch line without reduction.

So let's take a closer look at the flex tubing so commonly used for this application. The manufacturer's label suggests that this is a 3/4 inch line, but wait - the label only states that the fitting is for a 3/4 inch connection. Example: 3/4 F.I.P.S x 3/4 F/M-S

I have 3 labels sitting in front of me all stating the connector sizes and one actually states the outside diameter. The inside diameter is what were concerned with since the ANSI/ASME standard that the TPR valves refer to for safe operation state - that the inside diameter of the piping may not be reduced. One more little detail is the sidewall strength of flex tubing, I'll just bet there's a minimum requirement and that the flex tubing doesn't make the grade.

Just a quick visual look and you can see that the flex pipe is significantly reduced - just past the connection the line is reduced to about a 1/2 inch O.D., for argument lets say it's 5/8ths. That's still an internal reduction of about 30%.

Temperature and pressure (T&P) relief valves used on residential water heaters are typically designed and manufactured and installed to the standards set by the ASME and ANSI testing labs.

The following warning was listed in the installation instruction sheet for a TPR valve found at Home Depot.

WARNING: To avoid water damage or scalding due to valve operation, discharge line must be connected to valve outlet and run to a safe place of disposal. Discharge line must be as short as possible and be the same size as the valve discharge connection throughout its entire length. Discharge line must pitch downward from the valve and terminate at least 6" (152mm) above a drain where any discharge will be clearly visible. The discharge line shall terminate plain, not threaded.

Excessive length over 30' (9.14m), or use of more than four elbows or reducing discharge line size will cause a restriction and reduce the discharge capacity of the valve. Discharge line material must conform to local plumbing codes or ASME (A112.4.1)requirements.

To ensure proper operation, this valve must be installed by a qualified service technician or licensed plumbing contractor in accordance with these instructions and the local plumbing codes and standards. Repair or alteration of valve in any way is prohibited by national safety standards/local codes.

That's my story - and I'm sticking to it -- Bob Kille

Doing a bit of research on the internet as to the verbiage of ASME (A112.4.1 - 1993 Water Heater Relief Valve Drain Tubes) I run into a brick wall unless I want to cough up the $35 bucks to download the PDF version of this study.

Suffice it to say that I did locate more than one source that confirmed the above warning as accurate and also made reference to the fact that the line should be smooth, as in NOT corrugated or wound as in the case of flex tubing.

Now that you've got most of the facts together - will you be calling out this condition for repair? I'm still on the fence on this one until I talk to the local building officials as to their position. I suggest you do the same just in case the use has been approved by the local building inspector.

How else could we possibly explain the use of copper flex discharge piping in new installations? Incompetence? Never, not from a public official. That's my story - and I'm sticking to it.