PVC Failure

[Nick Bacon]

has anyone seen this before?  We just noticed a failure on the 2" PVC on the influent line going into our spray-erosion chlorinator booster pump for both our hot tub and our zer-depth entry pool.  It looks like a straw that has collapsed on itself due to suction.  Neither me or my Facility Superintendent have EVER seen anything remotely close to this.  The H2O temp is 88 and 104 for the 2 pools and the air temp doesn't go past 90 depending on the temperatures outside the building.  Any insight other operators have would be MOST helpful.  THANKS!

[Jesse Benavidez]

EDITED@10:12pm 8/14/12

I have not seen anything like this before, however, I do have a couple of thoughts.  If I am reading this correctly, the booster pump is in-line and gets its water from the filter system.

Being that this is part of a spa/warm pool, sch40 pvc may not be the best choice.  Sch 40 2" has a 280psi max pressure at 73f.  Suction max for 2" Sch40 PVC is 84GPM.

For 140f, you have a max pressure of 61psi. Your body of water may be a max of 100f or so, but your pump/filter/chemical system may be at a different temp.  Water exiting the boiler can exceed temps of 115f.  The heat can degrade the PVC creating a weak point.

Then your adding a suction pump to the mix.  PVC has a higher chance of imploding than exploding.  Just a couple of factors can create this type of failure.  A little stress overtime in my mind.

My fix for this, replace with schedule 80 cpvc.  Stronger and has a higher temp rating.

A little bit of reference

http://www.nationalpipe.com/printable/Plumbrite.pdf - Max Pressure

http://www.certifiedpoolinspections.com/flow.html - Max GPM for suction

[Cliff Pryor]

Jesse has a great answer for you Nick.  In any event, I would get that pipe replaced ASAP.

[Nick Bacon]

Thanks Jesse, we considered pipe failure due to heat/stress but I'm still put off by it happening to 2 pools on the exact same day.  We have 3 pools in that pump room and the third suffered no damage.  The hot tub I can see getting soft over time due to the higher temps and chlorine content, but our zero-depth pool is kept at 88.  Cliff we're rush ordering replacement pipe :)  Thanks for your input guys.

[Clemente J. Rivera]

All booster pump systems for chlorine feed should be plumbed in sch80 PVC. I'd have a talk with your installer...

[Craig Merkey]

I have only seen this once before and it happened when the pvc was hot.  The one I observed was pressurized and it bulged out rather than being collapsed.  It become brittle afterwards, so replace it!