Water Heater Temperature Pressure Relief Valve PIPING

[labman]

I can't answer you on the code. I do want to comment on a couple of other things.

The directions aren't near explicit enough about ''The cold water gate valve must be left open while a water heater is in use.'' Water must always be free to flow back out of a heated tank. Many places are now requiring a black flow preventor at the meter. One of them or any valve must have an expansion tank between them and the heater. A valve is OK, as long as you never shut it without shutting the tank off. If you want a valve to shut off the hot water, put one on the outlet.

The other thing is that gate valves have been obsolete for about 25 years since the low cost ball valves came out. For about the same price, the ball valves are quicker and easier to use, and leak less both externally and through them.

 

[XS650]

quote:

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Originally posted by labman:
I can't answer you on the code. I do want to comment on a couple of other things.

The directions aren't near explicit enough about ''The cold water gate valve must be left open while a water heater is in use.'' Water must always be free to flow back out of a heated tank. Many places are now requiring a black flow preventor at the meter. One of them or any valve must have an expansion tank between them and the heater.

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Now I know why the water heater in my new house has a pretty blue accumulator on the water line. Thanks.

 

[tom slick]

an expansion tank also helps with "water hammer"

I don't know what code is but I would want it to at least go down near floor level.
if installed on a second story you would want to plumb it into a drain.

 

[Pablo]

It is down near floor level...like 1"

I didn't put an expansion tank in. I know the purpose....well....we don't have a back flow preventer though.

 

[TheLoneRanger]

None have been plumbed, in the last 3 houses we've lived in. They have simply been screwed into the top of the heater, with the outlet coming straight out. They've all been installed in the basements, however.

 

[Pablo]

What is the code in your area? Does it have to go outside if your water heater is in the garage?

Old house - Existing WH (died) did not even have the valve plumbed. When the WH croaked I did the same. The house is being inspected Tuesday, so I decided to install some 3/4 copper pipe from the valve, like this: Water heater install

But I don't have a drain below. Just concrete floor.

 

[oilyriser]

A funny thing can happen when that relief valve starts to fail. The hot water leaks out when the tank is hottest, and flows to the lowest spot in the basement, creating a puddle. Then, because it was hot, the water immediately around the heater evaporates, leaving no trace of where the puddle came from.

 

[kenw]

T&P valves should not go to an existing drain pipe (this could back up boiling water into tub, sink and shower drains). It should be piped to an outside location on its own line. If your new one is in the garage, take it to the nearest wall and outside.

Slope it slightly down from the T&P valve to the nearest wall. Go to the wall and then 90 degrees straight down with a 90 degree elbow at the end to gop thru the wall and outside.

Ours has heavy wall PVC after about 3' of flexible copper, some codes may require galvanized or copper for the full length.

 

[XS650]

quote:

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Originally posted by tom slick:
an expansion tank also helps with "water hammer"

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It doesn't seem like it would help a lot since it's on the inlet to the water tank instead of the outlet where the nasty dynamics take place.

 

[brianl703]

I had to get a water pressure regulator installed at my rental property. It had severe water hammer problems, so I got a pressure gauge and connected it to the outside spigot..100PSI meter, it pegged out! Max is supposed to 85PSI per code.

So I called the county and asked them what was up with the water pressure and the lady said, "Oh, we made some changes to our system, you can get a pressure regulator if it's a problem..."

Gee, did you think about telling anyone?

Anyway, I called a plumber to get a pressure regulator installed and he installed it and said that if I saw any weeping from the pressure relief valve on the water heater I'll need an expansion tank. So I did and I had the expansion tank installed too.

 

[Not the Autorx Frank]

Pablo,

Just punch that copper line through the wall to the outside and you should be good to go. 1/4" per ft fall applies in all horizontal runs.

 

[oilyriser]

You also have to have a way to know if the valve is letting water out.

 

[Pablo]

Wall to outside is not so convenient. Oh well - goes to floor - inspector there 9 AM today.