In order to gain occupancy, an inspector informed me that I need to install a vacuum relief valve on the cold water supply line for my hot water tank. I purchased a vacuum relief valve and the installation instructions that came with it states that it should be installed on a horizontal line above an elbow... (directly above the vertical line that feeds the tank) My hot water tank is under the stairs in my basement so there is no room above the elbow for that valve. Does it matter where I install the valve? Can it be somewhere else on the cold water line? Or will I have to move the cold water line so its lower? I guess Im actually asking for clarification about the function of this valve... Thanks!

Hi Sland4...

A vacuum breaker is really just a backflow preventer. Here, in the case of a backflow condition, such as a fire department flushing water hydrants in your neighborhood the vacuum breaker will allow air to enter into the water system in such a way as to prevent water from getting sucked out of the waer heater which could result in a dry firing of the water heater which would break the water heater and be a real problem... huh?

That vacuum breaker needs to be installed about 6 inches +/- above the top of the tank. It needs to be installed AFTER the cold water shutoff into the heater.

You could install a 1/2" female x 3/4" female x 1/2" copper tee fitting right off the cold water nipple and then install the 1/2" vacuum breaker right into the 1/2" female part of the tee fitting.

If you don't have room for that you can install the vacuum breaker anywhere on the horizontal as long as it is after the shutoff, as mentioned... see pictures below... :)

Back to you...

MARK

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Hi Mark, thanks for the prompt reply. The cold water supply line is 3/4" pex and the shutoff is about 8" above the tank. The second diagram in your pictures shows the setup (two vertical lines above the tank) Does the breaker need to be above or below the shutoff on a vertical line?


Oh, when I posted my last response your diagram changed to show the cold water shutoff. I get it now! Thanks

Hey! That's cool. I had just finished posting the first drawing when I said, "OUCH"! I forgot the shutoffs! So I updated the diagram and reposted it... really funny how the question seemed unanswered without the shutoffs for both you and me... :)

Glad we're clear!

MARK

Just stumbled across this posting and massplumber2008's information is completely wrong. The advise is incomplete and this reply is probably too late. A vacuum breaker and a vacuum relief valve are designed for completely different applications.

Hi Pghplumber...

Welcome to AMHD.

I can see why you answered the way you did, but the way the question reads it is clear that Sland4 was talking about a vacuum breaker and NOT a vacuum relief valve... ;)

As an example, they said, "I purchased a vacuum relief valve and the installation instructions that came with it states that it should be installed on a horizontal line above an elbow...(directly above the vertical line that feeds the tank)". This is not the description of a vacuum relief valve... agreed?

Then, in post #3 Sland asks, "Does the breaker need to be above or below the shutoff on a vertical line?" If it was, indeed a vacuum relief valve, I would have expected Sland to correct me at this point.

I also figured that this job was being reinspected as Sland said, "In order to gain occupancy, an inspector informed me that I need to install a vacuum relief valve on the cold water supply line for my hot water tank."... so if I was off base I figure they would have been back by now to tear my head off!

Finally, I just posted all this to kind of show you what my thoughts were when I answered the question. After a few thousand (or more) posts you kind of learn to read between the lines.. ya know?

Anyway, thank you for posting your thoughts as you saw them. I completely understand and am glad you posted your safety concerns!

Again, welcome!

Mark

I still disagree unless the poster of the question can cite the model number and manufacturer of the vacuum breaker. I have yet to come across any code that states that a vacuum breaker is required on a domestic potable water system, before the hot water tank. There has been much confusion in the past, and there still is, over the difference between a vacuum relief valve and breaker. Sland4 may not have corrected you because they are not aware of the differences. To directly state that an inspector specified a vacuum relief valve and knowing that it is the common item on the cold supply of a hot water tank would indicate that a relief valve is needed. My goal is not to create conflict but to clarify to other visitors to this site that there are differences in the items and the details are important. A vacuum breaker, vacuum relief valve and back flow preventer are all different for different applications. Purchasing the wrong item, installing it then NOT being able to return it could become costly for a consumer. I've been reading between the lines for a few years with customers and it's always a crap-shoot if we actually hit the nail on the head. But if you can post a vacuum breaker for domestic hot water tank supply or post a code specifying a breaker, not a relief valve... you may convince me. I'll keep an open mind.

Pgh...

I see the issue now... ;) I stated that a vacuum breaker was needed when in fact a vacuum relief valve was the correct terminology as you (and sland4) pointed out. Sometimes, I get to reading so many of these I do, hopefully only on occasion, mistype something.

I appreciate the correction on that so others can't get screwed up by it all. As noted in my original post, however, the placement(s) of the vacuum relief valve is correct!

Thanks again!

Mark

Thanks for clearing that up. Vacuum relief valve is the right answer for that application. But do you need a vacuum relif valve on a domestic heat exchanger when the heat is by a steam coil?

Hi Rcmeke

Nope, a vacuum relief valve is not commonly installed on a tankless coil.

A pressure relief valve, or even a combination temperature and pressure relief valve, on the other hand, is 100% required on a tankless coil system... ;)

Mark

Hello, could you possible explain to me the difference between the two? (vacuum breaker and vacuum relief valve)

Thanks!

Still wondering in 2012? Usually a vacuum breaker is what is considered to protect the water system from syphoning contaminated water into the piping system, as in toilets, urinals, etc. A vacuum relief valve does in fact break vacuum but is more used in the line of "letting air in" so the hot water tank can be drained for service, like for heating element replacements, etc. A more complicated system like indurtrial plants and the like use backflow preventer valves. These protect the main water supply from contamination by preventing "back flow" from the facility to the water line in the event of a pressure drop or loss in the line. Good information can be found on Wikipedia as well.

Yes power plant mech is correct a vacuum breaker is to prevent syphoning,u will find these on application which will have a hose or some means of cross connection from water to sewer. So when at times there's a drop in city pressure an a syph comes on,if your running your sprinkler, before it comes back threw your hose bib your vacuum breaker will stop it. Your vacuum relief is designed to watch your heater not so much for draining an service purposes. It's a relief to help your TMP valve so in case it does pop off for extreme heat it will help TMP discharge faster by letting air in as well as cold water to prevent your house turning in to a mini nasa rocket lauch place.

We thank you for the information, however, You're responding to a 4 year old dead thread. Please check the date before you post. Thanks Tom