PVC Drains and Boilers Do Not Mix

Big-Al_2

I'm doing an industrial project right now, replacing an 28 year old 200 horsepower boiler with three 50 HP units, to be staged on as-needed. The contractor was getting ready to put in the drain pipes for blowdown, routing them into the existing floor drain from the old boiler . . . but something didn't look right. 



It turns out that the guys who built the boiler room back in the early 1980's had plumbed in the underfloor drain pipes with 8" PVC.  PVC softens at 140 degrees F.  From exposure to boiling hot water the pipe had sagged, broken, separated, and collapsed under the floor.  We tried to snake a camera in there, but it didn't get very far before it ran into a collapsed section. So far we've broken out concrete to replace about 30 feet of pipe with cast iron, but I don't think we've come to the end of it yet.  Water from the broken drainpipe had also started to undermine the floor. 



So . . . beware of piping floor drains with PVC . . . or even pouring buckets of hot blowdown water into PVC floor drains.



I'm sure I'm not the first one to run into this.  Anybody else have a story to share?

Charlie from wmass

Metal or nothing here

In Mass all commercial plumbing is copper or cast iron. The only place it is allowed is for chemical wastes that would damage the metals or for hotels and hairdressers. we are also required to pipe blow offs to tanks to temper the water down before discharging into the drains. The tank size is determined by the boiler HP rating.

Big-Al_2

New Boilers

PVC is the preferred material here for burial, even for potable water.  Acid soils can eat up iron pipe pretty fast, depending on the part of town it's in. 



New boilers have a blow down tank for tempering . . . the old one didn't.  That one was before my time.  I think the several hundred gallon old boiler might have been drained hot a time or two as well over the years.  That would cook a plastic pipe pretty well.