Water heater relief valve capacity/compliance

[TimNY]

What is the method to determine the capacity of a relief valve?

The scenario I have is wrong in more than one way, but it raised some questions for me. I have a 1/2" pressure relief valve installed in a bushing that is installed in the 3/4" tap on the top of the tank.

First issue, there is no temperature relief valve.

Second issue is P2803.3 says "shall be installed directly into a tapping"; would you say valve-installed-in-busing-into-a-tapping would be violating this section?

...and finally a question: valve may be installed in a water line close to the tank. So, a 1/2" relief valve could be installed and not violate P2803.3, but it must have an adequate relief rating.

I am looking at Watts specifications, but what is "adequate"? I am thinking that as long as it isn't discharging at static pressure, it should be adequate?

TIA

 

[north star]

Re: Water heater relief valve capacity/compliance

Have you checked the WH manufacturer specs.? If that manufacturer spec'd a 3/4"

"tapping" for their product, then the reducer busher installation [ with the pressure

relief valve ] is not compliant! In my view, the reducer bushing into the WH

tapping WOULD violate Section R2803.3. Also, Section R2803.1 requires a

temperature relief valve to be installed, or the combo type. Check the manufacturer

specs.

 

[Uncle Bob]

Re: Water heater relief valve capacity/compliance

Tim,

North Star pretty well covered it.

What year IRC are you reading from please? 2000, 2003?

" "shall be installed directly into a tapping"; would you say valve-installed-in-busing-into-a-tapping would be violating this section?"

A bushing or any other adapter means that the installation is "not installed directly".

Uncle Bob

 

[TimNY]

Re: Water heater relief valve capacity/compliance

Thanks for the replies.

I apologize, pseudo-2003 NYS codes here.

I agree, the bushing would not allow you to meet the "installed directly into tapping" requirement.

I realize a temperature relief (or combo) is also required.

In reality they are going to remove the bushing and insert a 3/4" t&p valve directly into the tapping, which will solve all the issues.

However, in reading the code it did make me think. Lets say you go to an inspection and a 3/4" temperature relief valve is installed directly into the tapping on the tank. A separate pressure relief valve, 1/2" in size, is installed "in a water line close to the tank."

Does it comply? How do you determine "adequate"? I started thinking about it, and it seems to me that the valve must be capable of discharging more GPM than there is supply to the house at xxx psi (xxx being the safe limit); it must also open at a pressure less than xxx psi. Or the manufacturer's instructions, of course. I have to find some and see if they actually mention it.

Thoughts? I'm just not sure how you prove or justify "adequate".

TIA

 

[Mule]

Re: Water heater relief valve capacity/compliance

The pressure relief valve can be installed anywhere within the system.

The pressure will be the same throughout the system.

Thr PRV could probably be of any size rated for XXX pressure as long as it is recognized for the minimum pressure.

Correct???

 

[TimNY]

Re: Water heater relief valve capacity/compliance

The pressure relief valve can be installed anywhere within the system. The pressure will be the same throughout the system.

Thr PRV could probably be of any size rated for XXX pressure as long as it is recognized for the minimum pressure.

Correct???

Pressure relief valve must be installed in a water line close to the tank.

Capacity is my question. If you install a 1/16" PRV that pops at 80psi, I don't think that is going to be "sufficient capacity" if your 15GPM submersible pump has run away.

I have deduced that the valve must discharge at least as must GPM as is capable of being delivered. Try getting that information on a well system.