# Bad BW tank weld or stress from Pex



## O.C. plumberman (Nov 21, 2008)

I was thinking a bad top weld on the 50 gallon (power vent) Bradford White W/H but could Pex stress do this? Or was it just a bad top tank weld waiting to go wrong? Btw,.... it was not like this from the time it was installed, this happened approximately 5 years later.


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## redbeardplumber (Dec 4, 2012)

Gotta be bad welds on those thread a lets ( proper term?) crazy never seen that before


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## love2surf927 (Dec 22, 2011)

I have seen this happen due to thermal expansion.


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## Redwood (Sep 8, 2008)

*Shut it off now and replace it immediately!*

That water heater has been over pressured and was attempting to launch mythbusters style!

It has overheated and the T&P did not release as it should have!

With gas water heaters the flue in the center holds it rigidly in place and the outside tank wall holds the outside edge in place. So a bulge develops between the outside tank wall and the center flue causing the crossing of the supply and outlet lines. In an electric tank without a flue the lines would bend outward.

The welds are great but they have been tested and I would call this a destructive test... 

I'd find a way to contact the customer right now and tell them to shut it off...

Seriously!


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## PlungerJockey (Feb 19, 2010)

It's not from bad welds.

That my friend is from thermal expansion. The water in the tank expands so rapidly the T&P valve cannot react fast enough.

Pull the expansion tank off and it will be water-logged and very heavy. I would bet that your water pressure may be high to. We see thermal expansion issues here alot. The expansion tanks that are used on residential are poorly made and seldom last much over a couple of years. 

The nipples pointing in are a dead give away. The pressure builds up and expands the center of the tank outward, which is why the the nipples bulge in.

I've also seen this problem on the FVIR waterheaters where the tank does not leak. The expansion of the tank distorts the burner chamber and the baffle tube which does not allow them to vent properly.

Install a new water heater and expansion tank and tell the home owner to test the expansion tank reguraly after 1 year. I say 1 year because most expansion tanks have a 1 year warranty.


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## O.C. plumberman (Nov 21, 2008)

Very interesting, this was a first for me, thanks for sharing love2surf927,Redwood and PlungerJockey. I learn something new everyday  I actually just went out for a look see after a couple other companies were out to make repairs. I think the first guy changed a sensor, I didn't touch it and told the homeowner to replace it a.s.a.p., and gave him a bid for a new W/H but never went back out....Also every time the customer would attempt to light the W/H it would instantly turn off. I think the Man upstairs had this guys back. Thank you very much guys if I ever see this again I'll know exactly what to do and what not to do thank God that W/H wouldn't re-ignite


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## PlungerJockey (Feb 19, 2010)

Watts has a pretty good explanation here
http://www.watts.com/pages/learnabout/thermalExpansion.asp


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## Redwood (Sep 8, 2008)

It is powerfully close to being this scene...


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## MTDUNN (Oct 9, 2011)

O.C. plumberman said:


> I was thinking a bad top weld on the 50 gallon (power vent) Bradford White W/H but could Pex stress do this? Or was it just a bad top tank weld waiting to go wrong? Btw,.... it was not like this from the time it was installed, this happened approximately 5 years later.


Did you have a look at the T&P? Was it ever capped?

This was no longer a water heater. It turned into a deadly bomb. I hope if you didn't already replace it, that you turned off the gas.


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## Redwood (Sep 8, 2008)

O.C. plumberman said:


> Very interesting, this was a first for me, thanks for sharing love2surf927,Redwood and PlungerJockey. I learn something new everyday  I actually just went out for a look see after a couple other companies were out to make repairs. *I think the first guy changed a sensor,* I didn't touch it and told the homeowner to replace it a.s.a.p., and gave him a bid for a new W/H but never went back out....*Also every time the customer would attempt to light the W/H it would instantly turn off.* I think the Man upstairs had this guys back


Okay...

Doom on the incompetent guy that worked on it... :laughing:

Good news that it won't stay lit...:thumbup:

And you made the right call...


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## love2surf927 (Dec 22, 2011)

It won't stay lit because the flue is pinched closed, good thing too.


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## redbeardplumber (Dec 4, 2012)

Crazy! Rare thing up here... Not many closed systems....I learned something too


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## PlungerJockey (Feb 19, 2010)

We have experienced a lot of growth in our area. We see the thermal expansion issues in the newer areas, with newer meter sets that have check valves installed. Anything that has a prv is also at risk.

The prv goes bad and allows higher pressure into the system, but provides a block for expansion.


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## redbeardplumber (Dec 4, 2012)

We have some rural water co-ops around here that have these meter sets with a backflow device. I was just working on one, and I had installed an expansion tank, the inspector commented that it was a good idea, but NOT CODE. Crazy especially after seeing that picture.


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## justme (Jul 4, 2012)

the expansion tank was probably never installed properly , you should pressure the bladder in the expansion tank to match the incoming pressure (before you turn the water on) or you might as well not install it at all.


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## MACPLUMB777 (Jun 18, 2008)

Redwood said:


> *Shut it off now and replace it immediately!*
> 
> That water heater has been over pressured and was attempting to launch mythbusters style!
> 
> ...



WHAT REDWOOD SAYS IS CORRECT I HAVE SEEN THIS MANY TIMES DOING 
WATER HEATER SERVICE WORK !


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## wyoredman (Oct 10, 2013)

justme said:


> ... you should pressure the bladder in the expansion tank to match the incoming pressure ...


Very interesting? I have installed several of these expansion tanks over the last few years, as our town has adopted a "double check" code requirement.

I have never thought to pressure the expansion tank.

Another question, many of the new homes going in around my State are manufactured modular types with pre plumbed water heaters. The home manufactures use very cheap WH. I have seen some with the inlet and outlet low on the tank with copper flex hooked to PEX running straight through the floor. In these situations, the only possible place for the expansion tank is under the home in the crawl space. Have you ever had any issues with expansion tanks located a distance (~5'+) from the WH?


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## redbeardplumber (Dec 4, 2012)

As long as the expansion tank is on the system somewhere, it shouldn't be an issue


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## Redwood (Sep 8, 2008)

The expansion tank really has little to do with the deforming of the tank and the crossing lines... It is a contributing factor but a small one....

The real problem and the critical problem is the T&P Valve failed to open and release the pressure when it should have...

Lets look at what a T&P Valve is...
2 functions... Lets use a Watts 100XL as an example

*Temperature:* When water temperature reaches 210°F (99°C) it is approaching boiling and converting to steam, at this point the 100XL is designed to open.

*Pressure:* When the pressure reaches 150psi (10.3 bar) it is at the maximum working pressure for the water heater and is designed to open. Actual burst pressure will be in the 300 psi range, I don't know the actual spec but typically burst is double the working pressure as a design rule of thumb in many other applications I know of. In the Mythbusters videos failure occurred at 330 psi so it fits...

Have a good read here...

And another one here...

And yet another one here...

The T&P should have opened long before the tank started deforming... :yes:


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## Plumberman (Jul 7, 2008)

wyoredman said:


> Very interesting? I have installed several of these expansion tanks over the last few years, as our town has adopted a "double check" code requirement.
> 
> I have never thought to pressure the expansion tank.
> 
> Another question, many of the new homes going in around my State are manufactured modular types with pre plumbed water heaters. The home manufactures use very cheap WH. I have seen some with the inlet and outlet low on the tank with copper flex hooked to PEX running straight through the floor. In these situations, the only possible place for the expansion tank is under the home in the crawl space. Have you ever had any issues with expansion tanks located a distance (~5'+) from the WH?


Says it plain as day in the installation instructions..


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## wyoredman (Oct 10, 2013)

Plumberman said:


> Says it plain as day in the installation instructions..


yep.

Guess we should ALWAYS read the installation instructions supplied with every piece of material. Doesn't really matter how we were taught, just what the instructions say!:laughing:

Thanks anyway for the heads up.


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## justme (Jul 4, 2012)

Plumberman said:


> Says it plain as day in the installation instructions..


I don't think any of us would be surprised at how many plumbers don't install expansion tanks properly, because of what they were taught by the plumber they worked for.


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## MACPLUMB777 (Jun 18, 2008)

redwood said:


> the expansion tank really has little to do with the deforming of the tank and the crossing lines... It is a contributing factor but a small one....
> 
> The real problem and the critical problem is the t&p valve failed to open and release the pressure when it should have...
> 
> ...



except for a water hammer that hits and bulges the tank before the t & p valve has time to open, such as a dishwasher or clothes washer valve snapping shut at the same time as thermal expansion!


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## Plumberman (Jul 7, 2008)

wyoredman said:


> yep.
> 
> Guess we should ALWAYS read the installation instructions supplied with every piece of material. Doesn't really matter how we were taught, just what the instructions say!:laughing:
> 
> Thanks anyway for the heads up.


On a pressure vessel yes sir we should...

Manufacturer specs trump how you were taught. What you were taught wont hold hot water if something fails and they refer back to installation specs supplied by a manufacturer when the buck is trying to be passed on to them.

Seen it many times...


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## Plumberman (Jul 7, 2008)

justme said:


> I don't think any of us would be surprised at how many plumbers don't install expansion tanks properly, because of what they were taught by the plumber they worked for.


Agreed


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## AndersenPlumbing (Jan 23, 2010)

This thread is a perfect example of why service plumbers need to join a forum like this. I think many have learned a thing or two by this thread. 


I had a similar situation like this a couple years ago. The customer opted to call more people for more estimates. They said in the mean time they would keep relighting. They were pissed off when I disconnected the gas and capped it!!! They were screaming at me. I told them that they would thank me when they all wake up in the morning alive.


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## love2surf927 (Dec 22, 2011)

AndersenPlumbing said:


> This thread is a perfect example of why service plumbers need to join a forum like this. I think many have learned a thing or two by this thread.
> 
> I had a similar situation like this a couple years ago. The customer opted to call more people for more estimates. They said in the mean time they would keep relighting. They were pissed off when I disconnected the gas and capped it!!! They were screaming at me. I told them that they would thank me when they all wake up in the morning alive.


Now that is truly providing a service my friend, might have saved their lives, of course they just thought you were an arsehole.... Typical.


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## Plumberman (Jul 7, 2008)

AndersenPlumbing said:


> This thread is a perfect example of why service plumbers need to join a forum like this. I think many have learned a thing or two by this thread.
> 
> I had a similar situation like this a couple years ago. The customer opted to call more people for more estimates. They said in the mean time they would keep relighting. They were pissed off when I disconnected the gas and capped it!!! They were screaming at me. I told them that they would thank me when they all wake up in the morning alive.


I posted a few years ago here about a similar situation.

This one was in an industrial plant. 100 gallon tank was severely rotten and the TP was not functioning..

They practiced lock out/tag out and we all had our own locks in the red bags with our name and contact info on them.

The original call was a recirculating pump that was fried. When I got there I saw how bad a shape the heater was in and locked out the pump disconnect and the gas valve. Told them it needed to be replaced and I wouldn't be removing my locks until it happened.

That was the last day I was ever dispatched to that particular plant and I'm sure they cut my locks off and put the heater back on line, but it wasn't/didn't happen by my hand.

No way I would have been able to sleep at night knowing I put something back into service that was a ticking time bomb. I've made a few enemies back in my service days by going above and beyond the call of duty...

One things for sure, I sleep like a baby at night knowing I provided a service that protects people even if they have a death wish... The way I see it, that's their own fault if they want to roll the dice on a faulty appliance.

What do we know, we just do this for a living, eh?


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## rjbphd (Feb 5, 2010)

We are a bunch of unsung licensed heros here as well others that are not here,yet.


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