# PEX and Water Hammer



## VictorPlumber (Feb 26, 2019)

Hello all:

2 years ago I replaced piece of pex-a pipe connected to 20 feet strait copper pipe going to outside hose bib (see the picture): I took out bursted piece and replaced with new pex-a piece. 

This is inside the house basement in a furnace room.

Yesterday I got the call from the same client – pex bursted again in a same place. I come and see the same picture I took 2 years ago. This time I replaced all the pex with copper. 

I figured it happened because of the water hammer from using fast closing pistol grip garden hose nozzle. 

Well... So much for pex hype... Watch out for pex...

What do you think about it ? 

Would appreciate your thoughts.


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## ShtRnsdownhill (Jan 13, 2016)

you may have some bad pex, never had a problem like that, how old is the pex you used? did it sit outside for long in the sun?
I doubt water hammer would split pex...you should do a little more investigating to the cause..


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## VictorPlumber (Feb 26, 2019)

Thanks for your reply.

1) It happened to pex-a. 

2) Two times In a same spot: June 2017 and June 2019. 

3) 2 years apart - so pexes from different batches. 

4) I never keep my pex in a sun – always in a cotton bag inside the van.

5) It wasn't an old pex - I buy a roll at my plumbing supplier and it is gone in a few month -> buy a new one -> and so on. Don't have old one seating around.

Thanks.


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## Tango (Jan 13, 2018)

Your crimps look way too tight. I doubt the pex is at fault, I bet something else is causing the split.


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## ShtRnsdownhill (Jan 13, 2016)

VictorPlumber said:


> Thanks for your reply.
> 
> 1) It happened to pex-a.
> 
> ...



pex a has a lower bursting point than pex b..what is the water pressure in the house? but even with that it shouldnt burst from water hammer..
does this client hook any pressure washer or any pumps to this hose bib? looks like someone back fed high pressure into the hose bib to burst pipe..


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## Debo22 (Feb 15, 2015)

Why are you crimping pex A? That’s expansion pex. They say you can crimp it but it voids warranty.


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## VictorPlumber (Feb 26, 2019)

Tango said:


> Your crimps look way too tight. I doubt the pex is at fault, I bet something else is causing the split.


I always check my crimps. Go - goes, NoGo - doesn't go. 

It happened right in a middle of the pex pipe away from crimp rings.

I use same crimper for about 10 years to all my pex connections - all good, never a problem.

I think pex can't take the water hammer pressure spike in this case. 

I changed it to all copper - we shall see what would happen.

Thanks


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## VictorPlumber (Feb 26, 2019)

ShtRnsdownhill said:


> pex a has a lower bursting point than pex b..what is the water pressure in the house? but even with that it shouldnt burst from water hammer..
> does this client hook any pressure washer or any pumps to this hose bib? looks like someone back fed high pressure into the hose bib to burst pipe..


Normal water pressure - 60 psi. No pressure washers, no pumps. 70 years old lady is living by herself.


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## VictorPlumber (Feb 26, 2019)

Debo22 said:


> Why are you crimping pex A? That’s expansion pex. They say you can crimp it but it voids warranty.


I always crimp pex-a - that's what my supplier sells - pex-a. 

Never heard crimping pex-a voids warranty on pex-a ???

Thanks


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## Tango (Jan 13, 2018)

Another thing I'm used to buying pex that has the black interior that looks like polyethylene. Your on the other hand looks see through and I wonder if it's less stress resistant.


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## VictorPlumber (Feb 26, 2019)

Tango said:


> Another thing I'm used to buying pex that has the black interior that looks like polyethylene. Your on the other hand looks see through and I wonder if it's less stress resistant.


I got it from wolseley canada. I always buy pex-a from wolseley canada.


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## Tommy plumber (Feb 19, 2010)

How hot does it get in that room during winter with the furnace running all day and all night? Maybe the heat is weakening that section of pex by expanding it. Then it contracts around spring time when the furnace shuts off. The expansion and contraction may be causing the bursting. 

Just a guess. This is just a theory that needs to be tested.


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## The Dane (Feb 19, 2015)

This looks to me as a case of frost in the pipes and the PEX burst because it is much weaker when short, than the copper. If the PEX pipe is really short, it has no room to expand much and becomes weaker than the copper pipe. It looks to me like that valve might have been closed and the pipe froze up and backed up the pressure back to the weakest spot which would be the close piece next to the valve. I would look at wether the hosebib is correctly installed or if maybe the hose was left on with the hosebib on too but inside valve off or maybe even enough cold airflow in the area to freeze the pipes.

Sent from my BLN-L24 using Tapatalk


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## skoronesa (Oct 27, 2015)

the dane said:


> this looks to me as a case of frost in the pipes and the pex burst because it is much weaker when short, than the copper. If the pex pipe is really short, it has no room to expand much and becomes weaker than the copper pipe. it looks to me like that valve might have been closed and the pipe froze up and backed up the pressure back to the weakest spot which would be the close piece next to the valve. i would look at wether the hosebib is correctly installed or if maybe the hose was left on with the hosebib on too but inside valve off or maybe even enough cold airflow in the area to freeze the pipes.
> 
> Sent from my bln-l24 using tapatalk







this^^^^^^^








.


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## VictorPlumber (Feb 26, 2019)

The Dane said:


> This looks to me as a case of frost in the pipes and the PEX burst because it is much weaker when short, than the copper. If the PEX pipe is really short, it has no room to expand much and becomes weaker than the copper pipe. It looks to me like that valve might have been closed and the pipe froze up and backed up the pressure back to the weakest spot which would be the close piece next to the valve. I would look at wether the hosebib is correctly installed or if maybe the hose was left on with the hosebib on too but inside valve off or maybe even enough cold airflow in the area to freeze the pipes.
> 
> Sent from my BLN-L24 using Tapatalk


In a furnice room ?


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## Venomthirst (Jun 20, 2018)

Definitely frost growing down pipe... improperly drained over winter... my cousins house did same thing last week was a bubble just like that and decided to pop off


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## chonkie (Jul 31, 2014)

Frostproof hose bibb? I bet it froze. I do remember reading somewhere there is supposed to be like a minimum of 7" of pex between fittings or it can do what it did.

Ps. Sorry if i repeated stuff others have already said. I can't read a damn thing on this post because that damn full page scrolling ad that covers all of the content is back.


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## Tango (Jan 13, 2018)

The pipe of the bib froze like 4 feet or more inside the house? That would be the first time I hear that especially if it's a warm room.

All the frozen bibs freeze where the valve ends (12"). The only way I can see it freezing 4 feet away would be an unheated basement or it doesn't have a real frost bib.


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## VictorPlumber (Feb 26, 2019)

This is in a middle of heated basement 20 feet from outside wall


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## Tango (Jan 13, 2018)

VictorPlumber said:


> This is in a middle of heated basement 20 feet from outside wall


You can rule out being frozen.


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## The Dane (Feb 19, 2015)

It's not likely but no you can't rule out frost.
Let's say that hosebib has those first 20' pipe connected to it being good copper and then it has those 3" of PEX before the shut off valve. Now what if the outside hosebib was left open with a hose attached and that hose had a closed pistol grip or other end to it and the customer closed the shut off valve inside. Now the hose and hosebib does not drain and the hosebib is open letting that outside frost create pressure that travels through the open hosebib and the warm water in the pipe inside now builds up pressure and before the first 20' of stronger copper splits you have that shirt weak spot in the PEX that bursts. 

My point would be that if the hosebib is left open and the inside valve is shut off and a hose is not letting the pipe drain out then it's not necessarily the hosebib that splits but rather what ever is the weakest spot in those 20' of pipe up to the closed valve and a short piece of PEX has been known to be weak.



VictorPlumber said:


> In a furnice room ?


Yes in a furnace room. Because of the build up of pressure I described.

I'll admit this is an unlikely case but non the less possible case.

Never rule out the rare chance because some times it's a weird thing going on. Just today I had trouble figuring out a no hot water case and it turns out that there was an off peak electric ripple control box that had been turned off which meant that I could read 120 volt on both wires but not get 240 volt total. This was weird to me and luckily there was a sparky in the house and he happened to realise what the problem could be.


In my opinion if it was some sort of waterhammer that caused it to burst then the OP should be able to fix the pipe and go open and close what ever valve it is and clearly hear if there is a waterhammer issue big enough to maybe cause trouble. 

My money is on some sort of frost causing pressure to tea me back and open the pipe in the weakest spot. 
I would replace the burst PEX with either copper or simply extend the PEX pipe to be a foot or two long.

Sent from my BLN-L24 using Tapatalk


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## skoronesa (Oct 27, 2015)

Yeah, I still think frost. I don't care where that pex was, furnace room or not. The cold end of that copper pipe started freezing and the water expanded creating much higher than normal pressure in the rest of the pipe. That valve must have been off. The pex was the weakest and couldn't take the pressure so it blew up like a balloon.




We had one job where a 1-1/4" propress cap was on a stub coming about 3' up from the floor of the mech room. The propress cap pushed off because of the pressure build up in the line from the other end partially freezing.












.


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## Tango (Jan 13, 2018)

skoronesa said:


> freezing and the water expanded *creating much higher than normal pressure in the rest of the pipe.*
> 
> 
> 
> .


That makes sense.


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## VictorPlumber (Feb 26, 2019)

Thanks


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## hanzkunzel (Feb 24, 2017)

I would cut in a gauge with a lyer hand on it and see what kind of pressure it gets to. I've only seen pex get that way due to freezing and always close if not at a fitting that transitions to hard pipe. I know I'm little late in on the subject and it's all been said, but I didn't see any mention of putting a gauge on for a long period and see what it spikes to. So there's my 2 cents.


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## VictorPlumber (Feb 26, 2019)

Thank you all for your responses


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## EastWestPlumber (Sep 10, 2017)

I've worked with this kind of pex in the past and the only time I've seen it split like this was due to freezing conditions. Is the hose bib installed in a colder climate? If the home owner isn't draining out the hose bib each winter but turning off the isolation valve in the picture it could be that freezing water is expanding the pex and making it weaker. It might explain why it takes a couple of years to break. Maybe it needs to have freezing water creating back pressure over a couple of winters to wear it down? Of course if the winters don't get very cold this doesn't apply, or maybe the hose bib installed has the long stem design that self drains, and so this would not be the problem in that case either.


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## breplum (Mar 21, 2009)

Scary looking.
I would like to forward the pic to the mfr's rep of that product.
Our reps have a lot of experience and can often be helpful.
At the recent builders PCBC show in S.F., a mfr of CPVC was showing samples of some very bad looking pex samples that were deformed and chemically deteriorated. Scary.
I am still a fan of PEX, but would want to get answers, for sure.


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## justme (Jul 4, 2012)

I would put money on frozen all day. That is too short of piece of pex to survive being frozen.


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## sparky (Jan 8, 2014)

The Dane said:


> This looks to me as a case of frost in the pipes and the PEX burst because it is much weaker when short, than the copper. If the PEX pipe is really short, it has no room to expand much and becomes weaker than the copper pipe. It looks to me like that valve might have been closed and the pipe froze up and backed up the pressure back to the weakest spot which would be the close piece next to the valve. I would look at wether the hosebib is correctly installed or if maybe the hose was left on with the hosebib on too but inside valve off or maybe even enough cold airflow in the area to freeze the pipes.
> 
> Sent from my BLN-L24 using Tapatalk


Yes what Dane said,you need at least 8inches of clear space between fittings for it to expand and not rupture,I bet a hose was left on it but they will swear up and down no one left a hose on it but they do it all the time


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## jakewilcox (Sep 3, 2019)

VictorPlumber said:


> Normal water pressure - 60 psi. No pressure washers, no pumps. 70 years old lady is living by herself.




Any chance you have used a "lazy hand" gauge to see where the pressure goes at a maximum? I have found this to be useful -around here, pressure will be like 60 PSI during the day and can jump to over double that late at night. Just my $0.02.


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## ShtRnsdownhill (Jan 13, 2016)

jakewilcox said:


> Any chance you have used a "lazy hand" gauge to see where the pressure goes at a maximum? I have found this to be useful -around here, pressure will be like 60 PSI during the day and can jump to over double that late at night. Just my $0.02.



I got a different use for my lazy hand..:devil3::devil3::devil3:


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