plumbing the TP valve

[Trying2Help]

Water heater is inside the house and would like to plumb temp/pressure release valve to the outside of house. Can I use CPVC for this? All the way, part of the way or no way???

[Ejbogusch]

I prefer installing a gas shut of device in place of the T&P valve when a water heater is located in the home with no existing T&P plumbing. This device screws in where your existing T&P valve is. Your gas line runs through this device so when the water temp exceeds its rating it shuts off the gas supply to your heater. This would be much easier and cheaper to install.

[majakdragon]

I respectfully disagree with Ejbogusch on this one. What happens to the pressure that is ALREADY in the tank. If it doesn't have an escape route and someone opens a faucet, it could get nasty.
CPVC should be fine for running this piping. In Florida we had to end at a tee. The line from the heater ran into the side of the tee and pipe was put in the lower end going to a French drain. The water could be seen (if leaking under pressure) through the top of the tee. You cannot reduce the size of the line coming from the heater to the end of the line. Good luck.

[Ejbogusch]

Let me clarify my above post. Automatic Gas Shutoff Valves are used in gas water heater applications to protect against overheating water in the domestic hot water supply heating system. It is an immersion-type valve that automatically shuts off the gas supply to the heater if the temperature reaches 210°lF (99°C). It is a self-contained device that consists of Buna-N disc-to-metal seating, manual reset button to reopen the valve after an automatic shutoff, trip latch assembly and stainless steel spring seats to close the valve at a controlled temperature, and thermostat with extension tube which operates trip latch in response to water temperature. The design certified by CSA.

Actually the pressure is not any more than if you opened your faucet while a standard T&P valve is discharging or a failed pressure regulator. This initial burst is from the water stored in the homes plumbing rather than the heater. The discharge lacks constant volume. On the plus side you take away the fuel that would otherwise continue to create an explosive situation that is trying to continuously vent out from the plastic pipe. Not to mention if this happened while you were on vacation.

[notuboo]

When I install a auto gas valve, I always install a pressure only valve on the cold water line somewhere convient to expell excess pressure. It's a new and improved code thing here in parts of my metro area.

Now for the original question....

Cpvc on the T&P line. Actually a local code issue. The problem you will run into regardless of material is, you have to be able to see if the T&P valve has a full open and postive closure when you activate the handle on the valve, while standing at the water heater. If you hard pipe the entire run, you can not see if this happens. (this is a NFG and IFG code requirement not plumbing codes)

[majakdragon]

I guess it's Back to Code time. Check your local Plumbing inspection office for what is acceptable in your area. This is one problem we have at DIY. We are from all over the world and codes vary from city to city.
I have told you what we had to do in Florida and Notuboo has said what he has to do. You also have an answer on what one member prefers. None of this may satisfy YOUR local code. Good luck.

[Trying2Help]

Well, talked to the City Code guy today. He says, it is okay to use CPVC. Asked him about the gas shut off and got something like this: "Well, they are coming up with new things all the time. If the package says it can replace the TP, than I guess it is alright." :wall:
He didn't say anything about "having" to be able to see the flow from the water heater. I asked if there was any need to be able to this and he said, "No." Hmmmmmm.
So, guess I will not push the use of a gas shut off, as I would think you would also have to have a pressure release somewhere in the line, close to the water heater and I would still have to vent that to the outside.
At this point, I am going to run a hard pipe all the way. It will be exiting the house near the front door, so if it is running or dripping the owners should be able to see it when they get home each day. Yes, there will be an elbow at the end so it will spray down, if the TP does pop off.
I also decided to enclose the pipe as it goes along the backside of the closets. This way if there is a leak and the TP pops off, there may be a wet spot but nobody will get squirted in the eye with hot water. It will also help to protect the pipe from someones high-heel getting thrown in the closet.
In any event, I think this is a better deal than not having anything install on the TP. Right now if the thing was to pop off it would go all over the floor in the hallway of the house.
Thanks for all the input and I will let you all know how it goes. :coffee: