What is this pipe for?

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RyanB

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About 1' above my gas water heater on the cold water inlet is a T that goes from 3/4" copper (cold in) to 1/2" copper. This 1/2" elbows back up 90 deg. to a brass T. The top of the brass T is capped with a threaded fitting. The side of the brass T goes to a 1/2" pvc that elbows back down approximately 3-4' and then elbows back into the wall and out the siding of my house where it terminates in an open 90 deg elbow pointed toward the ground approximately 3' off the ground. I'm about to replace my water heater myself and install a thermal expansion tank and I would really like to know what this extra piping is.
 

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RyanB

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It is a atmospheric vacuum breaker
Thanks, Frodo!

From what I'm reading, I would only need that if my water heater is located above the highest fixture in my house in case of a vacuum in the system. My water heater is in the garage on the first floor. The house is on a slab, so the only fixtures lower than the water heater are my outside spigots. Do I really need this?
 

Diehard

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Curious as to why an atmospheric vacuum breaker would have a pipe routed to outdoors?

I would look very closely at that device to see if there is information imprinted on it.

Also, Vacuum breakers are typically only required on bottom fed water heaters.

It is piped as if it was a relief valve yet the tank appears to have a T&P Relief on the side.

I suppose someone could have put in some type of pressure relief valve, which was set lower than the typical pressure setting of a T&P Relief valve with the idea that it could take the place of an expansion tank.

Just guessing, of course.
 
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frodo

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Thanks, Frodo!

From what I'm reading, I would only need that if my water heater is located above the highest fixture in my house in case of a vacuum in the system. My water heater is in the garage on the first floor. The house is on a slab, so the only fixtures lower than the water heater are my outside spigots. Do I really need this?
Was 'proly for an old water heater..that did not have a hole in the top of the dip tube
You should not need it on the new heater
 

breplum

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Looks like an adjustable pressure relief valve from an earlier installation.
Possibly an earlier installation had a Watts 210 temperature gas shutoff device and that "odd" relief valve is the required pressure relief, improperly installed on the cold side rather than the hot side.
 

RyanB

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I talked to a local inspector who said it is an expansion relief valve that is in lieu of a thermal expansion tank. He said at least up until 2015 it was still code compliant, and the builder (2001) probably installed this valve instead of an expansion tank to save space. I'll be plumbing in a tank with the new heater as it sounds like they're much more reliable. Thanks for all your input!
 

transcapeplumber

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That's interesting. Here in South Africa, the expansion relief valve is a critical component in a pressurized water heating installation. Expansion tanks are not used in domestic installations.
 

TomFOhio

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The relief valves are installed on the side of the water heater. They are very critical here also.
 

Diehard

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That's interesting. Here in South Africa, the expansion relief valve is a critical component in a pressurized water heating installation. Expansion tanks are not used in domestic installations.
Is that in addition to the tank mounted unit?
In other words set at a much lower pressure relief setting?
 

hukre

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Since there is no expansion tank, the PRV on the side of the tank was taking care of overpressure and released a certain amount every so often. I have seen this at several houses, and some of the owners put a small bucket on the floor below the discharge pipe that goes down along the water heater.
After a while, they got tired of always emptying the bucket, sometimes they forgot to empty it, or the kids would kick it over, so they ask a plumber to route the discharge pipe through the wall to the outside.
The plumber however told them that this was against the code, which it would be.
This leads me to believe that this was the case here, so a plumber installed another PSV off the water line, set at a lower pressure, and routed it to the outside to stop the annoying dribble inside the house.
(Installation of a small expansion tank would have been my preferred solution)
 

transcapeplumber

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Is that in addition to the tank mounted unit?
In other words set at a much lower pressure relief setting?
No, no expansion tanks on domestic systems. The mains water pressure is reduced to the water heater's rating by means of a pressure reducing valve. And almost all pressure reducing valves have an expansion relief function built into them either as a component on the body of the valve or as part of the pressure reducing function. This expansion relief activates each and every time water is heated. The pipe terminates outside and people put buckets or herbs etc to try to make use of the wasted water. In most instances it's just wasted. The water heater itself is fitted with a TP Valve which only activates in a fault situation. I believe, because we don't have very high risk of freezing conditions in most parts of the country for most of the year, this is the way the powers that be have decided to go. I would prefer a expansion vessel. There will be one less valve that can fail and much less water wasted in an increasingly water scarce country.
 

Dan the Plumber

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No mystery...It's a pressure relief valve. Maybe a combination temperature and pressure relief valve. Not the best location for temp. but ok for pressure.
 

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