# Vaccuum relief valves on water heaters



## Master Mark (Aug 14, 2009)

I am wondering if anyone has ever heard of a water heater imploding because it did not have a vaccuum relief valve installed on it...?? 
This is a new one on me.

I am just having a debate on another forum about this issue. Someone installed one on the top of a new water heater and it tripped open and flooded out someones home to the tune of $60,000..

. The plumber stated it was code to have one.... but their was no catch drain or anything to prevent the thing from flooding the home.

so this makes me wonder how many areas of the USA is this vaccuum relief valve required on a water heater?? It is not required in Indiana.... apparently it is required in New England.

also has anyone actually seen an imploded water heater in their plumbing travels??...anyone got a picture of one


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## Chandog (Nov 22, 2010)

Technically the newer dip tubes should negate the need for a separate vacuum breaker, however here in NH, most inspectors will fail the job if they don't see one. 

I have seen several Bradford White water heaters implode. I don't believe it had anything to do with the vacuum breaker or lack of. I think they were just bad tanks.


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## justme (Jul 4, 2012)

All vacuum Relief Valves are used for in water heater/tank applications to automatically allow air to enter into the piping system to prevent vacuum conditions that could siphon the water from the system and damage water heater/tank equipment. Never heard of an implosion , they are used here to keep the water from siphoning out of an overhead electric water head and burning up elements.


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## PlungerJockey (Feb 19, 2010)

The Rheem marathon w/h have to have them. The plastic tanks will expand due to pressure without problems. If you remove the vacuum breaker and drain the tank it will crack it everyone.

I had a customer try to change the elements on one. He tried to air lock it, but that did not work due to the vaccum breaker. He removed the vb and replaced it with a tee, with a cap. He managed to airlock it and replace the element, but it caused the tank to crack.

It also voided the warranty.


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## Master Mark (Aug 14, 2009)

Chandog said:


> Technically the newer dip tubes should negate the need for a separate vacuum breaker, however here in NH, most inspectors will fail the job if they don't see one.
> 
> I have seen several Bradford White water heaters implode. I don't believe it had anything to do with the vacuum breaker or lack of. I think they were just bad tanks.


 
yes, there is a hole in the dip tube that prevents a water heater from siphonage, and the need for this device seems to be more of a "make work" thing to me..


also , I wonder who gets to pay for the damages if
one fails and floods out the home..a few weeks down the road??
Has anyone ever seen one fail and flood out a home??

So When you install one on the heater do you try to figure out a way to run some sort of catch drain from it to a pan or drain ??? 

or do you just gamble on it and hope it never floods someone out?? 

just asking the questions for my own education


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## justme (Jul 4, 2012)

Sounds like this plumber needs to get the manufacturer of the VB involved and find out why the VB failed in the first place. We have been putting them in for years here and I have never seen one fail like you are talking about. Why would this VB have failed unless someone had shut the water down after the new heater and VB had been installed , who shut the water off and didn't check everything out once they turned it back on or did it fail while the water was on ?


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## Chandog (Nov 22, 2010)

I just gamble that it won't leak. Just like every other repair I do!


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## Chandog (Nov 22, 2010)

Seriously though I have only ever seen very old vac breakers drip and corrode. I've never seen one blow out. If the water heater is in a finished area I install a drain pan and floodmaster anyway.


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## Best Darn Sewer (Dec 23, 2012)

PlungerJockey said:


> The Rheem marathon w/h have to have them. The plastic tanks will expand due to pressure without problems. If you remove the vacuum breaker and drain the tank it will crack it everyone.
> 
> I had a customer try to change the elements on one. He tried to air lock it, but that did not work due to the vaccum breaker. He removed the vb and replaced it with a tee, with a cap. He managed to airlock it and replace the element, but it caused the tank to crack.
> 
> It also voided the warranty.


Damn. Good to know. I would never have thought that could happen.


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## love2surf927 (Dec 22, 2011)

I am new to this concept I have never heard of or seen one on a heater. Excuse my ignorance, but can someone please explain how a hole in the dip tube breaks the vacuum when it is completely submerged, I'm not understanding this concept. It seems to me if the tank is imploding due to a vacuum/siphon the manufacturer should be making the tank stronger period. The tank works off of a siphon if it fails under normal operation it should be on the manufacturer. This should be a non-issue in my opinion. Maybe I'm missing something. Again excuse my ignorance, can someone clear this up for me??


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## Chandog (Nov 22, 2010)

The vac breaker is there to limit back siphoning of the water heater. If the tank starts to siphon out the inlet, the hole in the top of the dip tube will break the siphon because air will come in. I don't think it has anything to do with preventing tanks from imploding.


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## MTDUNN (Oct 9, 2011)

Chandog said:


> The vac breaker is there to limit back siphoning of the water heater. If the tank starts to siphon out the inlet, the hole in the top of the dip tube will break the siphon because air will come in. I don't think it has anything to do with preventing tanks from imploding.


Yes If you remove pressure from the tank, that little hole will prevent a siphon back out


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## Best Darn Sewer (Dec 23, 2012)

love2surf927 said:


> I am new to this concept I have never heard of or seen one on a heater. Excuse my ignorance, but can someone please explain how a hole in the dip tube breaks the vacuum when it is completely submerged, I'm not understanding this concept. It seems to me if the tank is imploding due to a vacuum/siphon the manufacturer should be making the tank stronger period. The tank works off of a siphon if it fails under normal operation it should be on the manufacturer. This should be a non-issue in my opinion. Maybe I'm missing something. Again excuse my ignorance, can someone clear this up for me??


When you turn the water off to a building to repair a leak on the cold side, if the water heater is above the area you are working, it will siphon the water out of the tank via the dip tube due to a vacuum being on the system from you cutting the pipe and the water draining. In Houston our tanks are commonly in the attic so they require vacuum reliefs here for elec heaters. As stated before though, most dip tubes now have the hole at the top to prevent from siphoning past the top of the tank in a vacuum situation. 

If I am working on say, a 2 handle tub faucet, (with a water heater located above the faucet) when I remove the cold side stem, after the initial residual water drains, the water heater begins to drain or siphon, really, via the cold side and now hot water is is steadily draining out of the tank through the cold side of my faucet. It won't stop until you shut off the valve or the water level drops below the bottom of the dip tube.

I always shut off the water to the tank when I'm working on the water lines because most tanks have no vacuum relief and many lack the vacuum relief dip tube. It saves a lot of hassle. Where water heaters are located in a basement or crawl space below the water lines, there's rarely an issue with this.

And I have never heard or seen a water heater implode. I've seen plenty expand or explode. Its new to me.


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## wyrickmech (Mar 16, 2013)

So the vacuum breaker is just to prevent back siphon. Not vacuumed in the tank. If the tank collapse from vacuum just from draining the line there is a much bigger problem. The only place I have ever installed vacuum breakers for protection of the tank was on steam water heaters and coils in ahu,s. If you put a vacuum breaker on a water heater what kind do you use?


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## justme (Jul 4, 2012)

wyrickmech said:


> So the vacuum breaker is just to prevent back siphon. Not vacuumed in the tank. If the tank collapse from vacuum just from draining the line there is a much bigger problem. The only place I have ever installed vacuum breakers for protection of the tank was on steam water heaters and coils in ahu,s. If you put a vacuum breaker on a water heater what kind do you use?



one like this 


http://www.watts.com/pages/_products_details.asp?pid=815


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## Best Darn Sewer (Dec 23, 2012)

wyrickmech said:


> So the vacuum breaker is just to prevent back siphon. Not vacuumed in the tank. If the tank collapse from vacuum just from draining the line there is a much bigger problem. The only place I have ever installed vacuum breakers for protection of the tank was on steam water heaters and coils in ahu,s. If you put a vacuum breaker on a water heater what kind do you use?


A watts vacuum relief. It threads into a tee approx 6" above the tank on the cold side between the valve and the tank.


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## wyrickmech (Mar 16, 2013)

justme said:


> one like this http://www.watts.com/pages/_products_details.asp?pid=815


we never install these here. I do see the benefit to them but we still don't do it


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## TX MECH PLUMBER (May 27, 2011)

justme said:


> one like this
> 
> http://www.watts.com/pages/_products_details.asp?pid=815


Yep. An atmospheric vacuum breaker. 
Here any heater that us feed on the bottom must have a vb

If the cold feed line is lower then then the heater you must 90 up above the heater set a tee with vb and drop back down to feed the heater


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## wyrickmech (Mar 16, 2013)

TX MECH PLUMBER said:


> Yep. An atmospheric vacuum breaker. Here any heater that us feed on the bottom must have a vb If the cold feed line is lower then then the heater you must 90 up above the heater set a tee with vb and drop back down to feed the heater


good god one minute we are installing extra pressure reliefs then bladder tanks for thermal expansion and now vacuum breakers just in case the water goes into a vacuum. We need a supplier that makes a package deal all in one purchase.


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## TX MECH PLUMBER (May 27, 2011)

No. That would make it easier for hacks. The more components the better


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## wyrickmech (Mar 16, 2013)

TX MECH PLUMBER said:


> No. That would make it easier for hacks. The more components the better


yes I agree but the statement was (we need a supplier ) that will make it harder for the hacks to get all the parts at one stop


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## TX MECH PLUMBER (May 27, 2011)

Easy. Start requiring plumbing license to purchase water heaters !!! Like a/c equip


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## Master Mark (Aug 14, 2009)

Just my oipinion here but I have never heard of anything so completely un-necessary and outright dumb... 

some fellow from Georgia had $60,000 worth of damage cause the vrv somehow let loose and flooded the home...  it seems like something just waiting to fail some day..... and who gets stuck with paying this insurance claim if it fails a few weeks down the road??


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## Plumberman (Jul 7, 2008)

Master Mark said:


> Just my oipinion here but I have never heard of anything so completely un-necessary and outright dumb...
> 
> some fellow from Georgia had $60,000 worth of damage cause the vrv somehow let loose and flooded the home... it seems like something just waiting to fail some day..... and who gets stuck with paying this insurance claim if it fails a few weeks down the road??


It looks like its a supposed "fail safe" against siphoning the tank if the main is compromised etc. I didn't read all the post so sorry if its been said before.

Why not just install a main line backflow?


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## RealLivePlumber (Jun 22, 2008)

The tag in the picture says "extreme vacuums":laughing:

That's funny right there. 

I guess if it was 900' up in the air..................

I think its an old wives tale.

And they are required here, if a fixture is located below the outlet of the tank.


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## wyrickmech (Mar 16, 2013)

Plumberman said:


> It looks like its a supposed "fail safe" against siphoning the tank if the main is compromised etc. I didn't read all the post so sorry if its been said before. Why not just install a main line backflow?


yes why not a 007 double check on the cold feed.


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## Master Mark (Aug 14, 2009)

Plumberman said:


> It looks like its a supposed "fail safe" against siphoning the tank if the main is compromised etc. I didn't read all the post so sorry if its been said before.
> 
> Why not just install a main line backflow?


 

 good question.. 

the more I look at the water heater picture , it appears it might be for a manufactured home...because I have never, ever seen one pre- installed on a water heater before.....

of course the odds of having a water heater impolde and crack the inside glass liner of the tank is close to impossible .... at least in our state


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## Plumberman (Jul 7, 2008)

Master Mark said:


> good question..
> 
> the more I look at the water heater picture , it appears it might be for a manufactured home...because I have never, ever seen one pre- installed on a water heater before.....
> 
> of course the odds of having a water heater impolde and crack the inside glass liner of the tank is close to impossible .... at least in our state


The only time I have seen them here is on dialysis feed water systems. The heater is stand alone for the system and used to pre heat the water to a set point for optimum RO water. 

With a floor sink directly under it in a concrete floored mechanical room. 

Makes no sense to have it in a home.


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## Chandog (Nov 22, 2010)

Marathon water heaters come with them pre installed


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## SewerRatz (Apr 25, 2009)

A vacuum breaker is not the same as a vacuum relief valve.

The vacuum relief valve is to prevent a vacuum within the tank. This is an issue if the tank is located above any fixtures or if the tank is bottom fed. They have been required in Illinois for a long time. The oldest code book I have is from 1991 and it's in there, as well as the most current code listing the state has. 

Here is how the Illinois code states the need for a vacuum relief valve:

f)******** Vacuum Relief Valve.* Where a hot water storage tank or water heater is located at an elevation above the fixture outlets in the hot water system, or if the storage tank or water heater is bottom fed, a vacuum relief valve as listed in Appendix A, Table A (Approved Standards for Plumbing Appliances/Appurtenances/Devices) shall be installed on the storage tank or heater.


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## leakfree (Apr 3, 2011)

SewerRatz said:


> A vacuum breaker is not the same as a vacuum relief valve.
> 
> The vacuum relief valve is to prevent a vacuum within the tank. This is an issue if the tank is located above any fixtures or if the tank is bottom fed. They have been required in Illinois for a long time. The oldest code book I have is from 1991 and it's in there, as well as the most current code listing the state has.
> 
> ...


X2,been there in the book for a long time


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## Master Mark (Aug 14, 2009)

SewerRatz said:


> A vacuum breaker is not the same as a vacuum relief valve.
> 
> The vacuum relief valve is to prevent a vacuum within the tank. This is an issue if the tank is located above any fixtures or if the tank is bottom fed. They have been required in Illinois for a long time. The oldest code book I have is from 1991 and it's in there, as well as the most current code listing the state has.
> 
> ...


 
so are they required to be installed on all water haeters in your area or just on ones that are on a second floor in a home...above lower fixtures...???? 

have you had to install them much>>??

just wondering, we have literally at least 100,000 homes in this city with water heaters on the second floor of tract homes all over town and nothing like this was ever done..... 

 its never been a problem
probably because the dip tube has a hole in it that will stop the vacume and siphonage from happenning 

thanks for the info


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## up75 (Apr 18, 2012)

in wisconsin it say if the bottom of the heater is 20 feet or more above any outlet served by the heater it is required, but it is also required to be served by a floor drain or receptor


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## Master Mark (Aug 14, 2009)

up75 said:


> in wisconsin it say if the bottom of the heater is 20 feet or more above any outlet served by the heater it is required, but it is also required to be served by a floor drain or receptor


 
20 feet above any outlet served..... so here it would be only about 15 feet or less from the top of a heater to the fixtures on the floor below....

the floor drain and receptor seems a wise idea... I would not install anything like this without some sort 2x3 pvc cup zip-tied or attached somehow to underneath it to catch the water run off when it finaly gives out...


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## plumber tim (Jul 4, 2013)

In Mass every water heater is required to have a vacuum relief valve no matter where or how it is installed. Most older homes in Mass do not have RPZ's or pressure reducing valves. So in the unlikely event there is a fire on the street and they suck the water main dry with a pumper truck the water heater will not implode.


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## wyrickmech (Mar 16, 2013)

plumber tim said:


> In Mass every water heater is required to have a vacuum relief valve no matter where or how it is installed. Most older homes in Mass do not have RPZ's or pressure reducing valves. So in the unlikely event there is a fire on the street and they suck the water main dry with a pumper truck the water heater will not implode.


how much vacuum does it take to implode a water heater?


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## Master Mark (Aug 14, 2009)

wyrickmech said:


> how much vacuum does it take to implode a water heater?


I dont think its actually possible in the feild...:no:.

its probably only going to happen in perfect lab conditions....

I have not been able to find a legit picture of one that
just happenned on its own....


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## PlungerJockey (Feb 19, 2010)

Trust me it is possible on the Rheem Marathons with the plastic tanks.

I've never heard of it happening on a w/h with a steel tank.


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## wyrickmech (Mar 16, 2013)

PlungerJockey said:


> Trust me it is possible on the Rheem Marathons with the plastic tanks. I've never heard of it happening on a w/h with a steel tank.


most vacuum pumps use the same type materials for there tanks. I do not see any of them collapsing. The fiberglass tank I could possibly see. But I do not think a steel tank with a working pressure of at least 80 psi will ever implode. The most I could see it doing is siphoning water out of the tank and blowing a element if it was electric.


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## plumbdik (Aug 6, 2013)

TX MECH PLUMBER said:


> Yep. An atmospheric vacuum breaker.
> Here any heater that us feed on the bottom must have a vb
> 
> If the cold feed line is lower then then the heater you must 90 up above the heater set a tee with vb and drop back down to feed the heater



Same here. Code requires all bottom fed water heaters to have vacuum breaker to prevent back siphon.


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## SewerRatz (Apr 25, 2009)

Every heater that has fixtures below the heater or is a bottom fed heater I have installed a vacuum relief valve.


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## Master Mark (Aug 14, 2009)

*how rare are failures??*



SewerRatz said:


> Every heater that has fixtures below the heater or is a bottom fed heater I have installed a vacuum relief valve.


 
SewerRatz thank you for the info.... 

I am just curious to find out if you have ever had troubles with one of these vrv valves not re-setting properly after someone has drained the home down to do service repairs to fixtures?? 


I hate to even trip the t+p valve on a heater cause I know the odds are it 
will start leaking ...I just wont touch one....


So which brands are the very best and most reliable??

is this a rare occurance that one would fail?? 


and who gets to pay for the water damages 9 months down
 the road when one does fail??



like I already stated, their are at least 100,000++ homes in this city with the water heaters on the second floor sitting in pans to a cup drain with no vrv valve on them.... 

Its bad enough when the heaters flood out the pan and ruin the home...I hate to think what might happen with one of those acting up on a 10 year old heater..


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## SewerRatz (Apr 25, 2009)

We replace my mom's water heater every 7 years or so. Each one of these has a vacuum relief valve installed. We never had an issue with one leaking.

I have replaced 100's of electric 6 gallon water heaters that are secured in the ceiling space of public restrooms. They all have the vacuum relief valve installed. Once again not a single failure of the vacuum relief valve.

As for brands, my supply house always carry watts and that is what I see installed. When I replace a water heater and if it has a vacuum relief valve, and or an expansion tank, I replace both with the water heater. Just as it's a food idea to replace a check valve when you replace a sump/ejector pump.


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## MTDUNN (Oct 9, 2011)

SewerRatz said:


> We replace my mom's water heater every 7 years or so. Each one of these has a vacuum relief valve installed. We never had an issue with one leaking. I have replaced 100's of electric 6 gallon water heaters that are secured in the ceiling space of public restrooms. They all have the vacuum relief valve installed. Once again not a single failure of the vacuum relief valve. As for brands, my supply house always carry watts and that is what I see installed. When I replace a water heater and if it has a vacuum relief valve, and or an expansion tank, I replace both with the water heater. Just as it's a food idea to replace a check valve when you replace a sump/ejector pump.


I agree. I have never seen one leak. Same brand watts. 

Now T&P valves? I don't touch them either


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## GAN (Jul 10, 2012)

SewerRatz said:


> Every heater that has fixtures below the heater or is a bottom fed heater I have installed a vacuum relief valve.


Just curios. If you have a residence on a crawl space with the frost proof sill cock below the heater, do you install a VRV?


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## SewerRatz (Apr 25, 2009)

GAN said:


> Just curios. If you have a residence on a crawl space with the frost proof sill cock below the heater, do you install a VRV?


Yes. Granted the dip tube is supposed to prevent siphoning of the heater, but the hole might get clogged over time. Also what if the owner opts to install a hot & cold supplied sillcock.


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## Caduceus (Mar 1, 2012)

wyrickmech said:


> how much vacuum does it take to implode a water heater?


Depending on the diameter and thickness of the tank wall, approximately 12" Hg relative to vacuum or -8 psi relative to atmosphere. So, not much is needed to do it.


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## wyrickmech (Mar 16, 2013)

Caduceus said:


> Depending on the diameter and thickness of the tank wall, approximately 12" Hg relative to vacuum or -8 psi relative to atmosphere. So, not much is needed to do it.


it would take a lot of draw from a water line to get 6 in Hg much less 12 this is over kill. I have hooked up vacuum pumps that run29.7 in Hg and they are no thicker material than a water heater tank.


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## justme (Jul 4, 2012)

I say it's time someone takes a steel water heater tank and hooks it to a vacuum pump and video tapes it . Just to see how much vacuum it actually takes to implode it.


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## wyrickmech (Mar 16, 2013)

justme said:


> I say it's time someone takes a steel water heater tank and hooks it to a vacuum pump and video tapes it . Just to see how much vacuum it actually takes to implode it.


I agree and if it will not what then?


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## Master Mark (Aug 14, 2009)

someone already has done the vaccuum test, 
I saw it somewhere on the internet,,, 

I will attmept to look it up


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## justme (Jul 4, 2012)

I've seen video of soda cans , oil drums and other very thin wall material tanks . But I can't find a video of a water heater implosion. It would be interesting to see.


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## MTDUNN (Oct 9, 2011)

justme said:


> I've seen video of soda cans , oil drums and other very thin wall material tanks . But I can't find a video of a water heater implosion. It would be interesting to see.



Seen the 55 gallon drum implosion on mythbusters


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## UN1TED-WE-PLUMB (Oct 3, 2012)

Master Mark said:


> I am wondering if anyone has ever heard of a water heater imploding because it did not have a vaccuum relief valve installed on it...??
> This is a new one on me.
> 
> I am just having a debate on another forum about this issue. Someone installed one on the top of a new water heater and it tripped open and flooded out someones home to the tune of $60,000..
> ...




Side port water heaters require a vacuum relief valve on the cold side.. It's in the code book but I don't do much commercial work where most would be used. 

Something like .... If the water heater is the highest fixture.. Ie... In the ceiling on a platform. 


Imploded water heaters.. 
Yes I've seen a few.. Only residential 50 gasses. The bottom of the tank is blown out into the combustion chamber..( though not leaking..). And the taps in the top of the tank are blown out making the pipes coming off the top forming an "A" shape. What causes it? Not sure really. Possible t/p valve not opening.


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## Letterrip (Jul 28, 2013)

UN1TED-WE-PLUMB said:


> Side port water heaters require a vacuum relief valve on the cold side.. It's in the code book but I don't do much commercial work where most would be used.
> 
> Something like .... If the water heater is the highest fixture.. Ie... In the ceiling on a platform.
> 
> ...


Sounds like you are describing an explosion. They are referring to implosion. (Collapsing in on itself)

On the one occasion I had a side port heater on an upper floor, the inspector required a check valve on the cold side inlet. He only referred to siphoning, not implosion.


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