More on the Use of PEX Pipe

I just completed watching a webinar on “Designing Effective PEX Hydronic Piping Systems”. I have written on the subject of PEX piping before (See “The Problem with PEX Pipe” published 7/21/2012 and “Update – The Problem with PEX Pipe published 1/9/2013) and as a refresher, PEX stands for cross-linked polyethylene.  This is a chemical process whereby pipe is manufactured by cross linking elements of the molecules that make up the material.  The resulting pipe definitely has some advantages in terms of price and handling.  However, no matter who the manufacturer is, the pipe still has two major drawbacks: it is affected by UV radiation (sunlight and similar lighting) and it is made brittle by chlorine.  In the case of hydronic systems, these are systems that carry cooled or heated water for cooling and heating purposes, mostly found in large commercial and office buildings.  These types of systems don’t carry potable water and as a result are not susceptible to the deterioration caused by chlorine.  Since the piping is usually hidden, it is also protected from the effects of UV radiation.  The concern arises when PEX piping is used in plumbing applications to carry potable water to any end user.  Chlorine can and will attack the pipe and cause it to eventually leak.  Water leakage, depending on the location can result in property damage costing thousands of dollars to repair.  Some manufacturers use antioxidants to neutralize the effect caused by chlorine but, it can be “used up”.  That is, when the antioxidant effect has been depleted, chlorine will continue to attack the pipe as if the antioxidant were never there.  Uponor, the sponsor of the aforementioned webinar, has been contacted and questions submitted for their response but, we have not yet heard back from them.  If Uponor responds after this article is published, then we will pass along their comments.

The problem with PEX Pipe

Cross-linked polyethylene or PEX pipe has been on the plumbing market for a several years and has been accepted by most plumbers as an acceptable substitute for copper piping in potable water systems.  There are at least two methods by which PEX pipe is manufactured and depending on the manufacturer, theirs is the best way.  However, regardless of the method of manufacture, PEX pipe has a couple of drawbacks.  PEX pipe is subject to degradation by exposure to chlorine, ultraviolate radiation, and rough handling.  I bring this up because I am presently working on a case involving extensive water damage due to a leaky PEX pipe.  It seems that the pipe cracked longitudinally and released a great deal of water into the crawl space causing damage to the subflooring and consequently, the interior flooring as well.  This scenario isn’t unusual. But, after the hot water line was repaired, a second crack developed in the same line, only days after the first crack was replaced.  To make matters worse, a short time later, a third crack occurred, again, in the same hot water line.  It almost seems that the fact that a hot waterline is involved has something to do with the failures and there are accounts on-line of people having similar problems.  However, according to the manufacturer, as long as the conditions of the water do not exceed 80 psi and 140 deg, the piping shouldn’t be affected.  In addition, as long as the chlorine level is below 3500 parts per million, again, the piping should not be affected.  I’m not sure how accurate that information is since it tends to conflict with the pressure and temperature information written on the exterior pipe wall.  As for the chlorine level,  I have found reports stating that chlorine will continually degrade PEX piping, the greater the concentration, the shorter the service life.  I have also found that the failures affecting PEX pipe currently are similar to the type of failures that were affecting polybutylene pipe, for which there was a massive recall.  As far as I can tell, there are currently no recalls for  PEX pipe.

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