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Wenatchee and East Wenatchee Home Inspections- Per-P(l)EX-ing situation

By
Home Inspector with NCW Home Inspections, LLC

Wenatchee and East Wenatchee Home Inspections- Per-P(l)EX-ing situation

 PEX Tubing

The world of domestic water supply piping was destined to change when an English chemical company produced the first polyethylene plastic (PE) in 1933.

In 1968 a German inventor, Thomas Engel, developed a method that chemically cross link the molecules in PE. This produces a plastic that was stronger and more tolerant of high temperatures than standard polyethylene. Thus the X was added to PE to become PEX.

PEX A

Now we have three types of PEX; PEX-A (Engel method), PEX-B (Saline Method) and PEX-C (irradiation method). PEX-A is the most flexible version of this material.

The PEX-A Engel (peroxide) cross-linking method relies on peroxide being mixed with HDPE (high density polyethylene) and fed into the extruder under high pressure. The product is then passed through a long heated die where the cross linking takes place, caused by a chemical reaction between the peroxide and the polyethylene at a high temperature.

The PEX-B Sioplas (saline) cross-linking process was patented in 1968, followed by the Monosil (saline) process in 1974 and the Vinyl-saline copolymers in 1986. The difference in these methods is primarily in the way that the vinyl-saline and catalyst are added to polyethylene before it goes through the extruder. While some of the cross linking occurs in the extruder, the majority actually takes place in a water bath or in a sauna at elevated temperatures, after the tube passes through the extruder.

The PEX-C Electron beam (irradiation) method was made feasible in the mid-1970s. Of the three processes, the electron beam requires a substantially greater initial investment in tooling and machinery, costing millions of dollars. No chemicals are added or used in the cross-linking process; cross linking is accomplished after the tube has been extruded, coiled and placed in a special electron beam "oven."

Maniblok                                 Manifold

From my polling, PEX-A seems to be the preferred PEX by plumbers. There are some great advantages to this material (PEX). It is easy to run, you can create better sweeps/bends and if very flexible. It is highly resistant to bursting in cold weather. It can be set up on a manifold system very easily to create more even pressure throughout the home.

There is still some question on how will react with oxidizers (chlorine and fluorine) over long periods of time. Some manufacturers include stabilizer additives in the basic polymer formulation to sacrificially react with those oxidation agents.

 PEX A

PEX is fast becoming the plumbing standard in modern construction. (It has been used in Europe for many years now). Before then it was mostly used in radiant systems.

PEX tubing cannot be used in applications exposed to sunlight, as it degrades fairly rapidly. Leaving it exposed to direct sunlight for as little as 30 days may result in premature failure of the tubing.

Wenatchee and East Wenatchee Home Inspections- Per-P(l)EX-ing situation

NCW Home Inspections, LLC  is located in Wenatchee Washington serving Chelan County, Douglas County, Okanogan County and Grant County Washington.                                      

NCW Home Inspections LLC-509-670-9572

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Comments (6)

Charles Buell
Charles Buell Inspections Inc. - Seattle, WA
Seattle Home Inspector

Don good post---I am constantly calling out un-insulated PEX.

Mar 01, 2011 11:26 AM
Donald Hester
NCW Home Inspections, LLC - Wenatchee, WA
NCW Home Inspections, LLC

Charlie,

Pex or not it still needs insulation.

Mar 01, 2011 11:58 AM
Steven L. Smith
King of the House Home Inspection, Inc. - Bellingham, WA
Bellingham WA Home Inspector

Don,

Yes, the pipe may not be prone to bursting but it is hard to keep the house running when the water is frozen.

Mar 01, 2011 01:21 PM
Donald Hester
NCW Home Inspections, LLC - Wenatchee, WA
NCW Home Inspections, LLC

Steve,

Very true, but it is better to have house not running uncontrollably after the thaw ; )

Mar 01, 2011 01:52 PM
Dale Ganfield
Leland, NC

Hi Don, great post and info on pex.  Until this I assumed pex was pex and did not know the different types.  Thanks.  I follwed your QR code.  Nice website.

Mar 02, 2011 12:12 AM
Donald Hester
NCW Home Inspections, LLC - Wenatchee, WA
NCW Home Inspections, LLC

Dale,

Thanks. If you go to the different manufacturers they will all say that their process is the best. That they have a better percentage(65% to 89% is considered the normal range) of cross linking and greater homogeneity. No PEX is completely cross linked. And this will all very by how good of quality control the manufacturer has. The one thing that may be of note is those manufacturers of PEX that use the type A process tend to label their pipe as such. Type C is consider the worst process.

Mar 02, 2011 02:22 AM