Necessity of Vacuum Relief Valve - Not Pressure Relief Valve

Nail24 said:

...what causes the failure?

Click to expand...

A closed system without expansion tank or waterlogged tank could expose it to extreme pressure causing the failure. The TPR valve is meant to relieve pressure, not to save you from flooding, but rather to save you from an untimely death.

t
This is the first vacuum valve I've seen installed. How didi we ever survive so long? I've got a pressure relief valve on the heater for over pressure. The only benefit I see in this is to give the cleanup industry a job. I fail to see how a collapsing tank could injure anyone.

I just looked at some photos I took and discoverd the the vacuum relief valve is installed below the cold water feed line into the tank. I believe this is incorrect which would not allow an airpocket to be at the valve thereby causing a failure.

the dumbing down of everyone

Nail24 said:

t
This is the first vacuum valve I've seen installed. How didi we ever survive so long? I've got a pressure relief valve on the heater for over pressure. The only benefit I see in this is to give the cleanup industry a job. I fail to see how a collapsing tank could injure anyone.

Click to expand...

It is very stupid, extremely stupid, and in 99.99% of all homes its not necessary , and like you have stated, its only gonna cause huge floods and make work for the flood disaster folks......

this is just more red tape and government interference into something they dont have a clue as to what they are talking about.. They have been trying to jump start the economy for the last 5 years and have failed.......,

so now lets try making more work for the clean up industries and
all the other trades that will have to come along to repair these disasters....

if this jump-starts the economy going from the bottom up, who am I to
argue with the brilliant folks making the rules ???

again, you have a better chance of hitting the power ball twice in your lifetime
than ever having a water heater implode in your home..

Sue the installer for the damages

DIY Junior Member

---

Posts3

Won't go after the plumber. He's just complying with what the idiots that aren't plumbers are making him do for the glorious "CODE". Insurance it the issue here. If they find that I have not complied with the "CODE" they walk away even if compliance is going to cost them $60,000.00 in damage. This i the pinacle of insanity.

Being that it is a vent, it could conceivably suck in sewage if improperly connected to a drain. It would need a proper air gap.

Vacuum relief valves are "end line" valves, so there is absolutely NO WAY to install a "drain line" on them. They are also rated for 150 psi working pressure, just like most other plumbing items, so the T&P valve would not have allowed them to be "overpressurized". There are several reasons it could have failed, but only an inspection of it could tell for certain. Many of them contain a "spring loaded" ball and are installed vertically.

As you can see in the photo this one was installed horizontally. Is that incorrect? Shouldn't it be installed so that it will have an air pocket that is compressed to hold the valve closed rather than water?

How long would you expect an air pocket to last before it got absorbed into the water?

Don't know. That's why I asked the question. What fails in these valves to make them spew water all over the room?

everything fails

Nail24 said:

Don't know. That's why I asked the question. What fails in these valves to make them spew water all over the room?

Click to expand...

it could fail for a whole number of reasons ...just someone working on the
plumbing in the home could make it fail.......

I would guess that if someone simply shuts off the water to the building or in the neighborhood, it could potentially set this thing off with a loss in pressure in the system..... and just like the T+p valve once it goes off one time it probably ought to be changed out because it would begin to weep constantly

I would think that just age and time alone could set it off. someday..
just like t=p valves that begin to weep over time...they get lime and calcium deposits on them.

Now , this is just me ......but if I was forced to install them,
I would certainly cover my ass with some sort of catch drain.......

People shut off the water to their home for many reasons all the time to do maintaince to the home. If they open up a hose bib, this alone could cause some back pressure on the system. and it could easily trips one of these vaccuum breakers open.....and then the valve does not re-set properly due to age or calcification.......and pours out all over the house




..its just a matter of time before it corrodes up
and floods the hell out of everything.

this is just trouble waiting to happen in my honest opinion.

When I came across this thread it surprised me how misunderstood vacuum relief valves are. With the exception of hj, it seems that there is an impression of conspiracy from higher powers that created the VRVs to obtain power and money. I don't need to post a photo of a vacuum situation to prove that they occur. I've seen them and you probably have too, just didn't recognize them. It can happen to some top supplied tanks also. Not all tanks are made the same and wear, corrosion and defects are always a consideration when figuring out what happened. Referring to Master Plumber Mark's comments: There is an opportunity here to learn something and you seem to want to fight it. You have some ideas that are a bit off when commenting on relief valves in general (both vacuum and T&P) and might be misinforming those who visit this site.
I can see that these posts are a bit old, but felt I should comment anyways. You all will see it on your home page, I'm sure.

Please inform me how my comments are a bit off.... I dont mind....

the only point I am making is if you are gonna install one of these
you ought to do all you can to make them flood proof and keep yourself out of
future insurance lawsuits....

that is for both your sake and also the home-owners...


and I have yet to see any imploded water heaters here on this thread
that were not made to implode in a lab setting...

I'm with Mark on this and his general take on valves. I've learned from him.

Caduceus,
you dont actually say anything beyond a general ramble, for example, i'm sure that most folks know that there are different types, makes and makers, of w/h's out there. I'm also sure that you have much knowledge to share with us - perhaps you will share it, i'd like to learn more?

Here is a link to an archived Terrlove Forum thread that describes tanks that suffered from vacuum implosion. One of the first tell-tale signs are the crooked supply nipples (top or side supplied) and once the jacket is removed more damage can typically be seen, not that many people go through the trouble of removing it. The next time I come across one I'll get a photo, but until then check out the link.
https://terrylove.com/forums/archive/index.php/t-10664.html

The first descriptions in the thread of a damaged tank are usually caused by draining the tank with the supply valve off and no faucet(s) opened to relieve the vacuum. If the drain is then closed, the remaining moist air in the tank will cool and have an even more dramatic imploding action. That's why opening a valve during draining is important. The same scenario can happen if a faucet or other fixture is opened and there is a loss of positive pressure (cold water feed) on the system. This is more common with side supplied tanks, but not exclusive to them.
Fill a plastic water bottle with very hot tap water. Empty the bottle and put the cap back on tightly and set it aside to cool. It won't take long for the bottle to crumple in on itself. Modern vacuum relief valves are also more reliable than older designs and I have yet to see one leak, but periodic testing when you flush your tank should indicate if it's having operational or leaking issues.
Turn off power or gas to the hot water tank. Leave all faucets and fixture valves closed then close the cold supply valve to the water heater. Connect a hose to the drain of the tank to discharge the hot water somewhere safe from scalding. Open drain at the bottom of the tank. You should see the held pressure relieve from the tank quickly and then the tank will start draining by gravity. That's when you should hear the 'ssssssss' of the vacuum relief valve if it's working correctly. If you don't hear it hissing, open a faucet for hot water to relieve the vacuum and start filling your tank, close the boiler drain, continue purging the air from the tank and pipes and reset the tank for normal operation until you can replace the VRV.



Added Master Plumbers Picture

Maybe a more pragmatic reason to include one where I live is that it won't pass an inspection without one! It's a good idea, regardless.

I am confident that the pictured water heater did not implode.

This is the thread with that picture: https://terrylove.com/forums/showthread.php?10664-water-heater-implosion

Note even the original poster talked about the effects of pressure rather than a vacuum.

You are mistaken.

Reach4 said:

I am confident that the pictured water heater did not implode.

This is the thread with that picture: https://terrylove.com/forums/showthread.php?10664-water-heater-implosion

Note even the original poster talked about the effects of pressure rather than a vacuum.

You are mistaken.

Click to expand...

I agree that the photos appear to be more explosive rather than implosive. I guess Terry added the photo to my post in haste and may have confused the implosion/explosion issue discussed.
The first tank looks like the typical high-pressure, plugged/non op T&P valve expansion that I've only seen once in real life. But I guess that's all it takes is one time. The statements in my previous post regarding vacuums still stands true as well.



https://terrylove.com/forums/showthread.php?23656-Imploding-water-heater