Pex Burst!!?

[CA_Tallguy]

Thank goodness I was in the trailer at the time! I heard a loud groan and then 30 seconds later it burst. I'm guessing it formed a bubble before it went. The pressure at the airstream park where I am isn't very high so a neighbor doesn't think that was the case. Troubling!

The section of pipe that burst was under a bit of stress and bending so maybe that is more likely the cause.

[Skater]

That looks more like Polybutelene than Pex to me...the fitting below the hole looks just like the one I used to connect Pex and Polybutelene pipe.

Either way...that sucks! Wow.

[perryg114]

That is a classic overpressure failure. Consider getting a water pressure regulator and a gage down stream from the regulator so you can tell if it is working or not. If the regulator does not keep the pressure from rising with the valves closed then take it back and get another one.

Perry

[murreywalker]

The wall of the ruptured pipe appears to be much to thin to be PEX.

[perryg114]

It is not PEX probably PB. It is not a good joint. Why go from one size to another size and then to an elbow. It was rigged in the first place. Was that in the hot water side? It looks like the plastic was hot and soft when it went. I would expect old plastic to split in a more brittle fasion when at room temperature.

Perry

[Jammer]

Looks like PB to me too. PB loses its strength at high temperatures more rapidly than pex, probably got a little hot, a little over pressure, a little old and gave it up.

[CA_Tallguy]

That piping is run only on the hot water lines by previous owner. I don't know exactly what it is but will look for markings. It is stiff and actually probably thicker than it might seem from the burst. I never thought that material like that would bubble and burst.

Since it is only on the hot lines I was thinking it might be heat rated. Maybe not.

A few things may have contributed to this. One, the pipe was bending over the heater vent causing stress. And I guess there is some heat from the furnace there but maybe not extreme.

Second, there could be issues with the heat from hot water there as it is close to the water heater outlet. The water heater is a new tankless on demand from Atwood.

Third, I did end up going through some freezing weather not too long ago that did cause a little freezing of pipes. I think that section should have been on bypass at the time as it was before I had a functioning water heater there.

Now, I am just very nervous about this possibly happening again, and God forbid it should happen when I'm not inside the trailer. I will be replumbing at area to reduce stress from bends. May replace all the gray pipe while I am at it.

[Skater]

Originally Posted by CA_Tallguy

Now, I am just very nervous about this possibly happening again, and God forbid it should happen when I'm not inside the trailer. I will be replumbing at area to reduce stress from bends. May replace all the gray pipe while I am at it.

The PB pipe (polybutelene) was one of those things that looked to be a great idea...but it wasn't. There was a huge lawsuit that ended with a lot of homes being entirely re-plumbed, but unfortunately it did nothing for RVs like ours that use it. And, to top it off, the company that made it is out of business, so repairing it can be tricky.

I recently ran into a problem with my PB pipe - the pipe itself was fine, but the rubber gasket in the fitting on the water pump tore, causing a leak. I had to do exactly what it looks like your PO did - get a Pex fitting, a short length of Pex pipe, and then a Pex-to-PB converter. I used the Sharkbite stuff there because I need to be able to remove that connection easily for winterizing, but you can also crimp Pex (cheaper fittings, but you need a crimp tool).

Part of me just wants to re-do the entire trailer in Pex, but the other, saner, part of me realizes that's going to be a LOT of work that will likely involve connections in very-hard-to-reach spots.

In your case, I wonder why the PO didn't remove the PB pipe entirely - which makes me suspicious that it's a tougher connection that it seems from your picture. I'd look for a better angle fitting or rerouting the pipe to relieve that tension when you repair it.

Note - you can remove pipe from the Sharkbite fitting easily - there's a tool you can get at Home Depot that slides on the pipe, then pushes on the ring holding the pipe in place. The tool is less than a dollar. Good luck!

[perryg114]

Any plastic pipe near an exhaust vent will melt so whatever you do get it away from any source of heat. Check to make sure the water is not too hot which could melt pipes.

Perry

[CA_Tallguy]

Is pex preferable to copper? Part of me thinks it would be a good idea to run copper from the water heater for a good distance because it may be putting out really hot water at times, especially when there is very little flow. The water heater is a new Atwood on demand unit, as I mentioned, and it could be that water is getting super heated when it isn't flowing. On the other hand, It isn't really overly heating it with good flow I know, but I'm not sure what happens when flow is low like when a cold and hot valve are open at the same time (with just a tad of hot). It does require a certain amount of flow to even start heating, however, so I don't think there is a huge possibility that it is overheating unless something is wrong.

Copper seems safer if the issue is heat. But of course it probably isn't as good as pex should I get myself into a freezing situation unexpectedly.

[perryg114]

I am sure they should be some temperature settings for the unit as well as a flow range where it turns on and off that should be adjustable. I would contact Atwood and tell them the problem you experienced. Ask them what they recommend. High pressure + High Temperature + plastic pipes are not a good combination. I would think that the temperature coming out of the heater should not be any hotter than a standard tank unit reguardless of flow.

Perry

[Wazbro]

This quote from http://www.plumbersurplus.com/pdf/05108.pdf shows the temp ratings for PEX.

The American Society for Testing and Measurements (ASTM) has developed
minimum performance standards to determine PEX tubing’s suitability for
high temperature/pressure fluid distribution applications (F876) at three
different temperature and pressure ranges (160 psi @ 73.4°F, 100 psi @
180°F and 80 psi @ 200°F). All PEX tubing that is manufactured in
accordance with the ASTM F876 standard is perfectly suited for use in hot
water fluid applications at these temperature and pressure ranges if they
are marked on the tubing by the manufacture.

[CA_Tallguy]

Thanks -- I am thinking that those ratings are more than adequate as I don't think pressure in our systems is well under the 80psi and I think water output is also well under 200. I may run the first few feet of pipe out of the water heater with copper just to be safe. Maybe just the outlet part of the bypass so it might be easier to keep the water out of the copper segment should I encounter freezing weather.

[Skater]

I would avoid adding any connections as a result of the copper pipe - that is, run it to the next logical location for a connection. Personally I think you'd be fine with the Pex all the way - it's used in homes with on-demand water heaters, presumably - but if you think it's worth the extra complexity to install a length of copper, then I'd try to limit the complexity as much as possible.

Also, the water coming out of the heater (on demand or not) shouldn't be more than 120 degrees or whatever - otherwise it's a huge risk for scalding.

[perryg114]

Measure the temperature at the tap at the lowest flow rate the unit will operate and as long as it is below the temperature spec for PEX you are good. You can get a cheap digital probe type thermometer from Harbor Freight.

Perry