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Thread: Necessity of Vacuum Relief Valve - Not Pressure Relief Valve

  1. #31
    DIYer, not in the trades LLigetfa's Avatar
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    How long would you expect an air pocket to last before it got absorbed into the water?

  2. #32
    DIY Junior Member Nail24's Avatar
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    Don't know. That's why I asked the question. What fails in these valves to make them spew water all over the room?

  3. #33
    Master Plumber master plumber mark's Avatar
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    Default everything fails

    Quote Originally Posted by Nail24 View Post
    Don't know. That's why I asked the question. What fails in these valves to make them spew water all over the room?
    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.


  4. #34
    Master Plumber Caduceus's Avatar
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    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.

  5. #35
    Master Plumber master plumber mark's Avatar
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    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...

  6. #36
    DIY Member tom12's Avatar
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    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?

  7. #37
    Master Plumber Caduceus's Avatar
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    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.
    http://www.terrylove.com/forums/arch...p/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
    Last edited by Terry; 10-26-2013 at 09:22 AM. Reason: added picture

  8. #38
    Retired Defense Industry Engineer jadnashua's Avatar
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    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.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  9. #39
    DIY Senior Member Reach4's Avatar
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    I am confident that the pictured water heater did not implode.

    This is the thread with that picture: http://www.terrylove.com/forums/show...ater-implosion

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

    You are mistaken.
    Last edited by Reach4; 10-26-2013 at 11:04 AM.

  10. #40
    Master Plumber Caduceus's Avatar
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    Quote Originally Posted by Reach4 View Post
    I am confident that the pictured water heater did not implode.

    This is the thread with that picture: http://www.terrylove.com/forums/show...ater-implosion

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

    You are mistaken.
    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.



    http://www.terrylove.com/forums/show...g-water-heater
    Last edited by Terry; 10-26-2013 at 12:32 PM.

  11. #41
    Master Plumber master plumber mark's Avatar
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    Default none of you know what you are talking about

    The one picture of the blown up tank is from my store front window in Indianapolis...
    That tank and another one in the window are the only 2 water heaters I have ever seen
    that EXPLODED in the past 40 years......

    They are rare as hens teeth........
    they dont come along very often beause 99% of all of the t+p valves work correctly for decades....

    I still have not seen a legitimate picture of an imploded water heater that imploded natrually on its own.... because it is simply impossible to happen..
    I am still waiting for someone to post that picture of a real legitimate... in the field imploded heater......its going on over a year now...... so what gives here???


    The next water heater you have pictured has a problem with High Water Pressure
    and Thermal Expansion..... We see this a lot when a heater is in a closed loop system and the pressure has no where to go .....with no thermal expansion tank on it....

    here is a picture of a thermally expanded heater for your viewing pleasure..

    as you can see , the top of the fan motor is actually cracked from the inward pressure .
    of the union pipe nipples that were actually bent inwards due to THERMAL EXPANSION

    we took the top off to take a better look at the actual metal and its pretty amazeing that this heater did not split and blow up....

    Now Remember children, this did NOT IMPLODE.... it Thermally Expanded...



    If your state or region of the USA wishes to force you install a vaccuum relief
    valve on a water heater, then you better do it, no matter how stupid and absurd, or insane it totally is..... (like Obama care)

    All I am stateing is the obvious, they will leak and piss all over the place
    some day.....its only a matter of when......

    It would be wise to fugure out a way to install a overflow pipe to this vaccuum relief valve and into a drain....

    Odds are, you are gonna be named in a law-suit for the water damages it causes someday.

    I hope that your insurance comapny will pay for the huge $$ water damages is causes....

    please--just cover your ass







  12. #42
    Master Plumber Caduceus's Avatar
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    First of all, if there is a failure of the thermostat where the tank continues to heat and there is adequate high pressure to expand the tank to rupture, the thermal expansion tank becomes just another casualty of the situation once the pressure exceeds 120 psi. Tanks are typically rated to 300 psi or more when new and even when aged will hold more pressure than the thermal expansion tank bladder. Most of the time plumbers who install TETs don't pressurize them to match the building pressure anyways and end up blowing the bladder within a few weeks or months rendering the TET useless from that point on. But that is a matter for another day.
    Second, I would simply like to yield to Mark and agree that there is no need for vacuum relief valves. I have finally been convinced that the scientific conspiracy that has existed for over a hundred years regarding vacuums on water heaters and storage tanks is just that...a conspiracy to sell a useless product.
    Two years ago when I removed the 30 gallon hot water tank from the new pizza shop (another installer put it in less than a year before) because it was crumpled and leaking, I should have taken pictures to prove that it never happened. The pressure was regulated to 55 psi and the thermal expansion tank was in proper adjustment, but the fact that the tank folded in on itself due to a vacuum is a total lie. When the jacket was removed and I called the local rep to ask about warranty he stopped out and immediately confirmed my suspicion of vacuum since there was not a VRV in place and sent a letter to the owner explaining that the warranty was void, but I guess that I should have saved the letter that never really existed either...maybe I should have taken a picture of the letter, but it would also be as valid as a picture of the Loch Ness monster.
    So just to be clear in case this post just gets 'skimmed over' and not read in detail, like so many other posts, vacuums do not exist and never have. Watts and the other manufacturers have conspired with the water heater industry to sell you a useless product (they even print it in their owners manuals!!! those ba$tards!!) and they only need to be installed where required by code because the code enforcers either don't know what they are doing or they have also sold out and get kickbacks from the VRV manufacturers.
    Okay, now that the issue has been put to rest let's get back out there and save the world one clogged toilet at a time!
    Last edited by Caduceus; 10-27-2013 at 09:20 AM.

  13. #43
    Forum Admin, Expert Plumber Terry's Avatar
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    Here is some info from Watts

    For automatic venting of a closed system to atmosphere when
    a vacuum is created. The Watts N36-M1 Vacuum Relief Valve
    permits air to enter and prevent vacuum conditions that could
    siphon the water from the system, resulting in collapse of a
    tank or water heater or equipment burn out.
    Watts Model N36-M1
    Vacuum Relief Valve
    In the city of Bellevue, they want these on second story electric water heaters.

    Sometimes when we are doing a leak repair in a home, we will loosen the cold water connection to the water heater to break the siphon.

  14. #44
    Master Plumber Caduceus's Avatar
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    Quote Originally Posted by Terry View Post
    Here is some info from Watts



    In the city of Bellevue, they want these on second story electric water heaters.

    Sometimes when we are doing a leak repair in a home, we will loosen the cold water connection to the water heater to break the siphon.
    I guess you don't really get it, Terry. I'm trying to help you find your way over here to the smart and simple side of the discussion It has aready been confirmed that the vacuum relief valve companies made the valves and created a fictitious event that occurs in hot water tanks just to sell their useless product. My book from the International Library of Technology (Copyrighted 1905) explaining the fundamentals of vacuums, as well as the thousands of other proven experiences for over one-hundred years, are all untrue and engineers and plumbers who claim to have seen or experienced a vacuum in a tank are all liars. C'mon, don't get suckered by plumbers' myths.

  15. #45
    DIY Senior Member Reach4's Avatar
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    You are eloquent and lucid.
    Last edited by Reach4; 10-27-2013 at 10:49 AM.

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