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Flt_Simulation 07-10-2009 06:58 AM

Water heater pressure relief valve confusion
My contractor is about finshed building our new house here in the Philippines. I am installing an electric central hot water heater, but the instructions that came with this water heater (made in Italy) are very confusing and vague.

The water heater does not have a factory installed pressure relief valve like what is usually found mounted either on the side, or on the top of your average American water heater.

All they give you is the valve in a plastic bag and tell you to "T" it into the cold water inlet side (at least that's the way I understand the instructions). My Filipino plumber don't have a clue either. He has little experience with "central" water heaters, since they are not normally used in this country.

These poorly written instructions make no sense to me ... Since the fuction of a water heater pressure relief valve is to open up in the event that the water heater gets to hot and over-pressurizes the tank, I would think that this pressure relief valve should be "T"d into the hot water outlet side of the water heater. Then if the tank over-pressurizes, the valve will open and allow hot water and steam to be vented out of the system through an overboard vent pipe (see drawing below):

Here is where I think the valve should be ..... Anyone here agree?


Mike Swearingen 07-10-2009 07:10 AM

I'm not a pro plumber, but I fully agree with you. It should be installed on the outgoing hot supply line. I can't imagine a water heater not having a T&P valve installed on or near the top of the tank. Common sense.
Good luck!

Flt_Simulation 07-10-2009 07:42 AM

Mike ... Thank's for the input.

Here is a photo I just took of the valve that was supplied with the water heater and packaged in a plastic bag (slightly out of focus): :)

As you can see, it has male pipe threads on one end, and female on the other.

Mike Swearingen 07-10-2009 08:10 AM

Personally, I wouldn't use that one. It doesn't look that well made to me.
I would get a standard brass American Watts T&P valve (3/4" male threads) and have that plumbed off a 3/4" copper "T" with a female threaded fitting on the outgoing hot side. It will open at 150 psi and 210 degrees to prevent a steam explosion.
The discharge line should have a 6" air gap above the floor level.
Good Luck!

Flt_Simulation 07-11-2009 10:02 AM

Thank's Mike ... I will look for that valve here in the Philippines, but I got a feeling that parts for a residential water heater may be a little hard to find.

Sure would be nice if they had something like a Lowes or a Home Depot over here ... I would be in heaven!

BTW .... We do have a new Wallmart and a K-Mart here now: :laughing:

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