Thread: TPV discharge line of PEX? And where does it say TPV has to turn down?

I made a quick look of IRC and did not see where it specified the TPV discharge line on the exterior had to turn and face down toward the ground. Is this a code requirement? I think it is but did not see it.

Also, what I found was the TPV line should be of the same material as the supply piping. The house was PEX, so that would imply the TPV valve could be PEX also??

These was on Propane exterior wall mounted tankless heaters, by the way. See photos.

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The water heater T&P valve must run undiminished in size and terminate in an approved indirect waste receptor or outside and terminate 6" above finish grade (IRC 2803.6.1) ( not less than 6" nor more than 24" above finish grade UPC 608.5)

The lines must be pitched downward at 1/4"/ft and there may be no traps on the discharge line (IRC-2803.6.1 or UPC 608.5)

Mr. South:

There also appears to be no sediment trap on the gas line for this unit as per G2419.4. A drip leg may also be required depending on the gas supplier's analysis of the water content of the LP gas, as per G2419.2. Additionally, if the gas is wet, the gas line will need to be sloped downhill as per G2419.1.

Thanks guys.

The outlet providing power to the unit seems precariously located and should at least be upright.

Originally Posted by

The lines must be [B

pitched downward[/B] at 1/4"/ft and there may be no traps on the discharge line (IRC-2803.6.1 or UPC 608.5)

I don't think that was what he meant. I got that he was asking that if it had to have a 90 or 45 degree elbow pointing it down to the ground, instead of coming out horizontal (at a 1/4" per foot minimum slope). I wasn't aware that it had to point down, but I've been wrong before.

Okay, lets go with the TPR drain line should elbow towards the ground.

If that drain line is just terminating horizontally out of the wall as in his picture, can you imagine if you were walking by and get soaked with that 210 degree water?

For safety alone, it should be elbowed towards the ground.

rick

doesn't a "Pex" 90 reduce the inside diameter of the pipe????????????

RN

I don't have the current IRC in my computer and I am just too lazy to open the book.

2003 IRC: 2803.6.1 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 diameter of the discharge piping shall not be less than the diameter of the relief valve outlet.

If the discharge is not downward, then it could cause personal injury.
I don't know the i.d. of PEX, but if it is less than 3/4, then it is wrong-o

Part of the original OP's question was "can PEX be used as a discharge material"? I for one do not know and was waiting with baited breath for an answer. Perhaps someone knows this answer. Certainly if PEX fittings reduced the discharge diameter it would no longer work, but can the material itself be used if it can be configured properly?

My concern with pex is that is not a rigid and could allow any discharge to be sprayed around rather than directed to the floor.

Originally Posted by Mitchell Toelle

Part of the original OP's question was "can PEX be used as a discharge material"? I for one do not know and was waiting with baited breath for an answer. Perhaps someone knows this answer. Certainly if PEX fittings reduced the discharge diameter it would no longer work, but can the material itself be used if it can be configured properly?

PEX is an allowed material per IRC2006 P2803.6.1 #13; which refers to table 2904.5 of which PEX is listed. I'm not getting into the ID thing.

Originally Posted by Galen L. Beasley

My concern with pex is that is not a rigid and could allow any discharge to be sprayed around rather than directed to the floor.

Rick H. used to have a picture of a TPR drain line located on the side of a house that had popped. It looked to be copper, and it sprayed rather than "shot" to the floor which makes me believe that material would not make a difference in whether is sprays or not.

It was in the 2003 IRC but was removed in the 2006 IRC where the piping from a TPR discharge must turn down.

The 2006 IRC says...

6. Discharge in a manner that does not cause personal
injury or structural damage.

PEX is allowed if the installer can support it properly.

I would think you would need to use 1" material with PEX, so that the fittings would not reduce the passage below the TPR discharge size. What say you guys???

Originally Posted by Rick Hurst

Okay, lets go with the TPR drain line should elbow towards the ground.

If that drain line is just terminating horizontally out of the wall as in his picture, can you imagine if you were walking by and get soaked with that 210 degree water?

For safety alone, it should be elbowed towards the ground.

rick

Since the IRC merely says "injury", I always tell people that it should be pointed down. If I'm not mistaken, an inspector on this board was sprayed with hot water when he was walking past the outlet (exterior).

Bruce,

I think these are the ones your thinking of I've posted in the past.

rick

You find me a red colored pex that doesn't require protection from direct UV exposure and is according to the manufacturer and its approvals allowed to be used OUTDOORS and EXPOSED and I might agree IF IT WERE SLEEVED where it penetrates the brick veneer (pex flexes - that's why it is more resistant to freezing).

However, this is pictured going through the brick and exposed. I don't know of any Pex pipe or tube accepted for this use.

Next, the TPRV is wedged against the cabinet, it couldn't fully open if it needed to.Next the TPRV label tag has been removed. On that missing tag would have essential information. In that essential information (acceptance/approval based) is information such as that the discharge shall not be reduced.

You asked if a TPRV has to point down, and couldn't find it in the plumbing codes. That's because you'll find it in the Manufacturer's Instructions (usually on the yellow tag that's not supposed to be removed) for the TPRV. It (the TPRV) requires discharge the same size of the valve (usually 3/4") of the same minimum ID unrestricted. It further requires GRAVITY DRAINAGE that completely empties for the DISCHARGE from the valve (no traps, etc.) - you'll also find restrictions as to the total number of 90-degree bends or changes in direction being limited to four or less and usually a 30' maximum discharge length. Something to the effect of:

IMPORTANT: A relief valve functions in an emergency by discharging water. Therefore, it is essential that a discharge line be piped from the valve in order to carry the overflow to a safe place of disposal. The discharge line must be the same size as the valve outlet and must pitch downward from the valve.

Regarding the material for discharge being the same material employed for the potable plumbing system, that is not correct. It must be of a material that IS suitable/approved for potable plumbing i.e. the section list, but appropriate. i.e. you can have PEX for the plumbing system and copper tube for the TPRV, etc.

Pex requires restraint and support every x (most are usually 32") inches of run, at rise below floors or penetrations above, closer at changes in direction and support near valves.. TPRValves usually discharge at high pressure. When you pass PEX through metal cut-outs such as metal studs, etc. it should be protected from abrasion, it will move.

Assuming that is a 3/4" valve - the entire set up with the discharge using that restricted red PEX is a problem and the valve itself could not be opened to test, or fully open in the event of a temperature or pressure rise due to its restrictive positioning in that cabinet.


There are other issues there, such as the routing of the communication cable for the remote, the gas piping, lack of an air gap or indirect before outdoors (should valve be partially open, and sunlight area be submerged, or contaminated could contaminate the water supply) and others, but they weren't asked about in your original post, so I'll assume you noted those for yourself.

Originally Posted by Rick Hurst

Bruce,

I think these are the ones your thinking of I've posted in the past.

rick

As far as the first pic, what's keeping the owner from putting a shower head on that and using it to clean up from working in the yard?

What it comes down to is four things: 1) what the code says NOW; 2) what the code said BACK THEN; 3) what the manufacturer says; and 4) *the most restrictive of 1) and 3) or 2) and 3).

What the code says NOW:

- 10. Not terminate more than 6 inches (152 mm) above the floor or waste receptor

What the code said BACK THEN (from the 1997 SBCCI Plumbing Code):
- P504.7.1 Discharge. The discharge from the relief valve shall be piped full-size separately 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 (153 mm) above the floor. The end of the discharge pipe shall not be threaded.

The manufacturer said/says "at least 6 inches" above the floor, and used to say 'or grade'.

That pipe height is not the problem, the "discharge" is the problem, and that "discharge", as H. G. points out, must gravity drain, which mean it must "discharge" vertically down, and than must be "not more than 6 inches ... above the floor" AND "at least 6 inches" above the floor, which means *6 inches*.

The T&P discharge used to be allowed to discharge to the exterior, now, however, the discharge is required to be in the same room or space as the water heater. Times have changed and so have the requirements.

Its amazing how many times I report on something and then when the question is brought up by my peers, it makes me wonder if I am right with what I tell my clients.

In reading through the replies and it has been referenced several times about what the IRC says like Table P2904.5 does mention that pex is an acceptable material and P2803.6 does mention about the discharge pipe to be installed in a manner not to cause personal injury or property damage.

During my inspections I look for the discharge to point down and to not be more than 6" from grade or floor. I also look for the pipe to be a solid pipe such as a copper, stainless steel, or galvanized.

If I see anything other than above I write it up so my clients are aware of what I believe to be a problem although it may conform to the IRC.

The reason I look for a solid pipe other than a flexible copper or plastic pipe is because it is so easy to kink the flexible copper pipe or a plastic pipe which would greatly restrict or even block the discharge pipe. If that were to happen it does no good to have a TPR valve on the unit because the discharge line is blocked and if the valve was to open, it would still trap the pressure which could cause the HWH to burst or explode which is the purpose of the TPR valve in the first place.

Do you think that what I am telling my clients is the wrong thing to be telling them?

One thing I was waiting to see if anyone picked up on (Which H.G. did) is that the manufacture of PEX states it should no be exposed to direct sunlight (UV light). The manufacture states UV will cause the PEX to (eventually) break down.

All the other code that Jerry and others mentioned is right. The UV breakdown is just another reason why this was wrong, on top of the other mentioned code reasons.


*Hello Ricky, ....You of course as an inspector are entitled to tell your Clients your opinion, whatever you judgement tells you. As for me, I don't think I would express to my clients that a restriction in a flexible drain line could possibly cause a HWH to explode. I guess anything is possible but the likelyhood would be very remote I would suggest. CPVC (which is a somewhat flexible pipe) is listed and approved for TPV drains. I see CPCV drain lines weekly. I do not mention these to the Clients. Only if I saw a non listed or approved type of flexible material TPV drain line, would I bring it up. But even in that case I personally would not put it in terms of causing a HWH to explode.