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Cross-Linked Polyethylene PEX Piping Installation, Inspection, Safety

PEX cross linked polyethylene piping guide:

This article describes the properties of Pex Tubing or Piping, Cross-Linked Polyethylene (PEX). We discuss the uses of PEX tubing for water supply & in heating applications.

We describe the several differnt types of PEX tubing connector systems used including PEX crimp fittings, PEX compression fittings, PEX expander fittings, PEX Press-Fit connectors, and PEX Shark-Bite fittings and connectors.

We also discuss the ongoing debate of Pex versus Copper or other piping choices, with the pros and cons of each, and we include a literature review of and comment on the question is PEX tubing or piping safe to use or does it leach contaminants into our water supply. This article also includes the history of the development, use, & standards for PEX piping.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

Pex Tubing or Piping, Cross-Linked Polyethylene (PEX)

PEX Water Piping installation (C) D Friedman Galow Homes

PEX and PB plastic pipe are used for water supply in buildings use mechanical fittings (crimp and compression type) and we have found some installers using PEX tubing in low temperature heating applications (see below). PEX piping is also referred to as "cross-linked polyethylene" piping or just "PEX".

Our photo (left) illustrates PEX water supply piping being installed in a New York home.

Photo courtesy Galow Homes.

[Click to enlarge any image]

Article Contents

Applications & Properties of PEX Piping

PEX piping marking guide (C) Zurn ManufacturingInstalling both building water supply piping and heating supply piping (and radiant heating) can be significantly faster using PEX tubing because of its ability to bend around turns, avoiding some elbows, 45's and other fittings.

PEX piping is used in both hot and cold water applications (see the blue and red colors below). By convention the builder uses blue PEX for cold water and red PEX for hot water supply piping lines.

Generally you will find PEX piping or tubing marked with the nominal pipe size, wall thickness, and pressure rating and other information (see the illustration just below).

Temperature and pressure ratings for PEX, according to Zurn Manufacturing's engineering specifications is 160 PSI at 73°F, 100 PSI at 180°F, and 80 PSI at 200°F.

Illustration of PEX tubing markings - courtesy Zurn Manufacturing (permission requested 12/2010). [Click any image or table to see an enlarged, detailed version.]

When installing PEX piping, care must be taken that the pipe does not contact heating ducts.

If the pipe freezes, it is less likely to burst than and copper piping. Also, most types of plastic water pipe tend to sag and should be well supported by hangers

Watch out: PEX plastic water piping should not be installed outdoors or exposed to sunlight for long periods. The red and blue PEX piping shown below (right) were delivering hot and cold water in a newly-constructed home. The larger black ABS plastic pipe is probably a drain line.

Watch out: do not use plastic piping nor any other type of piping in applications for which it was not intended, or the result could be dangerous. For example, do not use PEX tubing for LP or natural gas piping.

Plastic piping (C) Daniel Friedman ... Polybutylene water piping guidelines Carson Dunlop Associates

PEX Tubing Connectors: Types, Tools, Requirements

Watch out: a variety of patented PEX tubing push-fit and clamp connecting fittings (at least six types) and connector crimping tools are on the market.

You may not obtain a proper and secure PEX connection if you mix tubing connector fittings and crimping tools improperly.

We recommend choosing a specific connector type and crimping tool and using it consistently at a given plumbing installation.

See PEX BRASS CONNECTOR LEAKS for an update on field reports of de-zincification corrosion and leaks at brass PEX pipe connectors, elbows & tees.

Examples & Photographs of the various types of PEX fittings and the special tools used include:

PEX Clamp fitting installation © D Friedman at InspectApedia.com


PEX Clamp fitting installation © D Friedman at InspectApedia.com

Shark Bite type PEX fittings © D Friedman at InspectApedia.com

PEX Tubing installation details © D Friedman at InspectApedia.com


Shark bite push fit plumbing fittings © D Friedman at InspectApedia.com

See PEX BRASS CONNECTOR LEAKS for an update on field reports of de-zincification corrosion and leaks at brass PEX pipe connectors, elbows & tees.

Types of PEX Cross-Linked Polyethylene Tubing

Four methods of creating cross-linked polyethylene, each possibly imparting different properties to the PEX piping or tubing, include

  1. PEX-A or PE-Xa = using peroxide, developed by Engel, PAM, Frankische and others, this form of cross-linked polyethylene uses peroxides (oxygen atoms with an oxidation state of -1) to provide the highest level of molecular cross-linking at the atomic level in the plastic as the plastic polymer is formed.

    PEX-A is the most-flexible and most kink-resistant of these forms of polyethylene tubing.
  2. PEX-B or PE-Xb = using silane, developed by DOW Corning / Sioplas. Pex-B is also referred to as "steam" or "moisture" cross-linked polyethylene.

    Unlike PEX-A, PEX-B cross-linking occurrs after the high-density polyethylene has been extruded into tubular form; the tubing is then passed through steam supplemented by silane (a catalyst) to form cross-links in the polymer tubing.

    PEX-B is not expandable and has a lowered kink-resistance.

    Excerpting from Conbraco, APOLLO PEX-B PIPE Submittal Sheet [PDF] Conbraco Industries, Inc., Matthews NC 28105 USA, Tel: 1-888-229-2874, Web: apolloflow.com
    Excerpts:
    PEX tubing is cross-linked, high-density polyethylene. It’s available in white, red, or blue colors for easy identification of hot and cold water lines. The silane method, also called the “moisture cure” method, results in PEX-B. In this method, cross-linking is performed in a secondary post-extrusion proce

    ss, producing cross-links between a cross-linking agent. The process is accelerated with heat and moisture. The cross-linked bonds are formed through silanol condensation between two grafted vinyltrimethoxysilane (VTMS) units, connecting the polyethylene chains with C-C-Si-O-SiC-C bridges.1 PEX tubing is for use in hot and cold potable water distribution systems as well as hydronic radiant heating systems.

    PEX tubing can also be used in “continuously recirculating” plumbing systems up to 140° F while maintaining chlorine resistance. The tubing may be installed in concrete, gypsum based lightweight concrete, sand, asphalt, in or under wood flooring, or behind wallboard or plaster.


    Watch out: do not try to connect PEX-B by shoving its end over a fitting that would cause expansion of the tubing. Doing so will lead to a plumbing failure and leaks.
  3. PEX-C or PE-Xc = using electronic irridiation. Unlike PEX-A, PEX-C cross-linked after the polymer material has been formed, but instead of using steam and silane (PEX-B process) PEX-C uses gamma radiation or an electron beam.
  4. PEX-D or PE-xd = using AZO (Gustavsberg-Lobonyl) - not currently in production

- Bean (2007)

Decoding PEX & Plastic Tubing Acronyms

  1. HIPS Polystyrene Tubing = High Impact Polystyrene Plastic Tubing: this is a high-impact-strength tubing, NOT-PEX tubing that is used in the food industry and other industrial applications.
  2. HDPE Polyethylene Tubing / PEX = High Density Polyethylene: posessing very good impact resistance, good rigidity, good heat distortion resistance at higher temperatures, a "fair" coefficient of thermal expansion, and a "fair" resistance to weathering when exposed outdoors.
  3. LDPE Polyethylene Tubing / PEX = Low Density Polyethyethylene Tubing, less costly, similar in properties to HDPE but less rigid.
  4. LLDPE Polyethylene Tubing / PEX = Linear Low Density Polyethylene: a form of polyethylene with increased flexibility, tensile strength, conformabilty, crack resistance. Described as imparting no odor or taste to water passing through the tubing.
  5. PETG Polyethylene Tubing / PEX = Polyethylene Terephthalate Glycol plastic tubing: this is a chemical-resistant tubing (does not tolerate outdoor exposure)
  6. POLYPROPYLENE (plastic) tubing: this is a lightweight NOT-PEX tubing that is heat resistant, used in automotivbe, food and beverage, automotive, appliances and other applications.

Example Colors of PEX Polyethylene Pipe / Tubing

Below the rainbow of 3/8" OD LLDPE polytethylene tubing is provided by FreshWater Systems.

LLDPE Polyethylene tubing in white, black, blue, red, green, orange or yellow from freshwatersystems.com cited & discussed at InspectApedia.com

In these examaple Pex tubing color choice photos, we show that PEX tubing or pipe is produced in a range of colors that include at least

Black, Blue, Gray, Green, Orange, Red, Yellow, White and also not quite "clear" but translucent such as Uponor TrffPEX SDR9 PEX-A tubing shown just below.

Uponor PEX water tubing (C) InspectApedia.com

Below: Black Viega PEX tubing [Click to enlarge any image]

Black ViegaPex tubing at InspectApedia.com

Below: Blue & Red PEX tubing installed in a New York home.

PEX Tubing installation details © D Friedman at InspectApedia.com

Below: two examples of green colored PEX and PEX-B tubing from SeaTech & Zoro.

The SeaTech PEX cross-linked polytethylene tubing shown here is manufacgtured in a range of sizes from 3/8" CTS (1/2" OD) to 1" CTS (9/8" OD), also 15mm and 22mm OD, and is rated for 160 psi and 80º F @ 100 psi OR at 72º F @ 160 psi.

Aqua-Green colored PEX Tubing from SeaTech cited & discussed at InspectApedia.com Green PEX tubing from Zoro Select cited and discussed at InspectApedia.com

The Zoro polyethylene pipe example is 1/4" OD, 5/32" ID, 3/64" wall thickness, 2" tubing bend radius, and rated for -50 D°F to 140°F.

Gray PEX plastic tubing cited & discussed at InspectApedia.com

Above: Gray Pex B02 tubing

White PEX tubing at InspectApedia.com PEX Clamp fitting installation © D Friedman at InspectApedia.com

Above: two examples of white PEX

Keep in mind that PEX or other types of plastic pipe or tubing may be installed but "disguised" by other coverings such as pipe insulation.

Below: an example of factory-insulated PEX tubing provided by Badger Insulated Pipe.

Insulated Pex Tubing from Badger Insulated Pipe www.badger-pipe.com cited & discussed at InspectApedia.com

Badger describes this product: This listing is for Insulated Pipe used for Outdoor Wood Furnaces/Boilers, Geo Thermal, Solar Heating or anywhere you need to transfer heated or chilled fluids. - retrieved 2019/11/08, original source: Badger Insulated Pipe W8359 State Rd 82 Mauston, WI 53948 1-800-571-7002 rsd@badgerpipe.com

Standards, Listings and Approvals for PEX Plumbing Systems

The following standards and building codes list at least some elements of PEX plumbing systems.

Pex Tubing / Plumbing use History & Dates

ABS (black) and probably PEX (red) drain and water supplyi piping photos (C) InspectApdia.com BnB Home Inspectins

Watch out: is this "red" plastic water piping PEX? No it is red-painted Polytbutylene pipe, discussed in detail

at PB POLYBUTYLENE (PB) PIPES

In the United States the use of PEX tubing in residential buildings for water supply & heating piping has been approved for use in all fifty states and in Canada in all of the provinces.

PEX Pipes vs Copper Piping: which is preferred?

PEX hot and cold water piping installed during new construction (C) Daniel Friedman Eric Galow 2012 2013Reader Question: Pex vs. Copper Water Supply Piping - which should I use?

Question: my daughter is doing extensive renovations on her house and the question has come up whether to use PEX or copper in the plumbing.

I did a google search and the informations is conflicted; see below

. [We read & also expanded the writer's original four web link citations in the article below - Ed.] Do you have knowledge of, and opinions about, this controversy? Any thoughts would be helpful. Thanks. Elisha Fisch, New York 2/17/2013

Reply:

Elisha I've moved this discussion on Pex pipes vs copper pipes to its own article at

PLASTIC vs. COPPER PIPES in BUILDINGS

We will continue to monitor the PEX health and contamination question and will update here. Contact Us by email to send field reports or to report on new studies.

Copper Water Supply Piping

The same PLASTIC vs. COPPER article above lists propertie of copper water supply pipes when used in buildings and compares copper pipe performance with that of plastic.

A bottom line opinion is that each plumbing material has its own vulnerabilities as well as advantages & disadvantages.

We discuss types of copper piping and their intended uses and copper fittings beginning

at COPPER PIPING in BUILDINGS.

Plumb-PEX Plumbing System Class Action Settlement - PEX piping leaks

In March 2012 people who own or previously owned a building where Plumb-PEX plumbing components were installed are notified of a proposed class action settlement involving Radiant Technology, Inc. and Uponor, Inc who sold Plumb-PEX insert fittings and stainless steel PEX tubing clamps.

Details about this PEX plastic piping failure are now at PlumbPex® PEX LEAKS & LAWSUIT

Also see PEX vs. COPPER Water Supply Piping - health & other questions

Kitec Brass Fitting & Related IPEX Plastic Pipe Leaks: Class Action Settlement

The Kitec system was a collection of brass plumbing connectors intended for use with PEX type plastic piping. Kitec, also in some sources spelled Kyetec is a brand of brass plumbing fitting that was recalled in 2005 by its manufacturer, IPEX, due to its tendency to quickly corrode. - Wikipedia [30]

Kitec plastic pipe and fittings has agreed to settle class-action suits in the United States and Canada for $125 million. The piping system that is the subject of this action was used in roughly 292,000 U.S. and Canadian homes beginning in 1995.

Details about the Kitec plastic class action suit are given in a link just below.

Question: is PEX the same as Kitec® ?

Is PEX the same as Kitec? How does one tell distinguish between Kitec and PEX? - Anon

Reply: Kitec was an individual brand of PEX pipe subject of a class action settlement

Anon,

PEX (cross-linked polyethylene piping) is a general term for a type of plastic piping used in water supply, heating, and other applications.

Kitec® is a specific brand of PEX tubing that was subject of a class action settlement with an end-date for filing claims of 31 March 2012.

  1. Details about plastic pipe leaks by pipe type & brand are in this topic home page:

    PLASTIC PIPE LEAK CAUSES
  2. Kitek® PLASTIC PIPE LEAKS, CLASS ACTION SETTLEMENT discussion is found within that article.
  3. PEX PIPING INFORMATION (this page) gives details about PEX across the product range
  4. Information about all types of plastic piping used in buildings starts

    at PLASTIC PIPING ABS CPVC PB PEX PPR PVC.

Pex De-zincification Update & Research: field failure photographs of Brass PEX Pipe Fitting Corrosion & Leaks

Brass PEX pipoing fitting corrosion (C) 2014 InspectApedia.com & Anon

[Click to enlarge any image]

Above left: brass tee corrosion appearing both on the Tee-fitting body (red arrow) and around the end of the PEX tubing (green arrow) on water piping in a 2009 home.

Details about corrosion, leaks, & possible dezincification problems at brass connectors used in PEX piping systems are

at PEX BRASS CONNECTOR LEAKS

PEX Piping vs Drinking Water Contamination & Pex Piping Installation Guides

 




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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2019-09-20 by (mod) - what size PEX for step and sidewalk de-icer / snow melt systems?

Bill

Please see your question and our detailed answer at

On 2019-09-19 by Bill

I have a radiant floor heating system for two rooms with 1/2" PEX that works fine. When I put it in, I used a manifold with an extra space in case I wanted to add a circuit.

We are going to repour front steps and sidewalk to the driveway and I thought that that would be a good use of my additional circuit. But I have read that any outdoor application should use 3/4" PEX instead of 1/2".

Can I mix have two circuits with 1/2" PEX and one with 3/4"? Can I just use 1/2" for the outdoor steps and sidewalk and expect it to keep the snow off? (I live in SE Michigan.)

On 2019-06-18 by (mod) - Wirsbo aquaPEX 1006 3/4 " piping leaks

RE-posting from private email:

Anonymous said:

Inspected a home with Wirsbo aquaPEX 1006 3/4 " piping.

My plumber claims the pipe fails and leaks at weak points and advised me to tell my client that replacement is needed

Was wondering if you have any hard facts and what your opinion is.

Moderator reply: Wirsbo, now Uponor PEX pipe & fitting failure report

Your plumber is correct, Anon, that there have been PEX piping leaks at some fittings. Leaks have been traced to

After reading up on PEX piping above on this page you will want to review

Details at PEX BRASS CONNECTOR LEAKS

There we show photos of old, leaky UPONOR TuffPEX (previously Wisbro some mis-spell as Wirsbo) seals in a PEX piping system as reported by an InspectApedia.com reader and we include an illustration of the newer, more-reliable insert seals for PEX connector that connect PEX tubing to plumbing fixtures.

On 2016-01-29 2 by Anonymous should you cross PEX pipes over one another?

should you cross the pipes over one another?

On 2015-12-26 by (mod) -

Not that I know of, Anon, but you can certainly ask your local building department if they have such restrictions.

On 2015-12-25 by Anonymous

hi. i want to know , is it against the building code to install pex water pipe in the restaurants ?

Question: installing PEX in concrete

(July 17, 2014) Anonymous said:

When putting pex in concrete do you need to pressurize the system before you pour the concrete?

Reply:

While I can't cite an authoritative reference, certainly I've never seen a system pressurized before installation.

I do see that the pex tubing is capped and supported above the slab to keep it acessible and clean at its connection points.


...

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PEX PIPING INFORMATION at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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