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To pex or not to pex? That is the question

Posted 05-04-2009 at 06:00 AM by faucetman886

As promised now a discussion of what I believe to be the most controversial form of plumbing piping on the market today…PEX (or crosslinked polyethylene). I say controversial based on the many discussion groups and forums that I read. PEX is discussed probably 10 times more often than any other form of plastic or metal piping as part of a water supply piping system even though it has several advantages over metal pipe (copper, iron, lead) or rigid plastic pipe (PVC, CPVC, ABS) systems. Some local codes aren’t allowing it for whole house systems and I believe, in general, it is the public’s lack of knowledge on the product that has caused most of the controversy.
PEX tubing is made from crosslinked HDPE (high density polyethylene) polymer. The HDPE is melted and continuously extruded into tube. PEX plumbing has been in use in Europe since about 1970, and was introduced in the U.S. around 1980. The use of PEX has been increasing ever since, replacing copper pipe in many applications, especially radiant heating systems installed in the slab under floors or walkways. Interest in PEX for hot and cold water plumbing has increased recently in the United States which I believe also contributes to the questions and discussions I read.

Advantages of PEX
1. Plumbing PEX plumbing installations cost less because:
o PEX is less expensive than copper pipe.
o Less time is spent running pipe and installing fittings than with rigid pipe systems.
o Installing fewer fittings reduces the chances for expensive callbacks.
2. Flexible PEX can be shipped and stored on spools, where rigid plastic or metal piping must be cut to some practical length for shipping and storage. This leads to lower shipping and handling costs .
3. PEX requires fewer fittings than rigid piping.
4. It can turn 90 degree corners without the need for elbow fittings.
5. PEX tubing unrolled from spools can be installed in long runs without the need for coupling fittings.
6. PEX tube fittings do not require soldering, and so the health hazards involved with lead-based solder and acid fluxes are eliminated. This makes it safer to install since no torch is needed to make connections..
7. PEX resists the scale build-up common with copper pipe, and does not pit or corrode when exposed to acidic water.
8. PEX is much more resistant to freeze-breakage than copper or rigid plastic pipe.
9. PEX tubing does not transfer heat as readily as copper, and so conserves energy.
10. Water flows more quietly through PEX tube, and the characteristic "water hammer" noise of metal pipe systems is virtually eliminated.
11. PEX can be used in combination with metal or other plastic piping and is currently most often used as connectors on existing system when old lines must be replaced in an existing system.
12. Each supply line typically has a shut off line in place for repair convenience
13. Pex is available In colors making easier to color code your plumbing system or easily identify hot and cold pipes.
14. A “manifold” system can be made as a part of the PEX installation allowing better segregation of hot and cold lines and better regulation of pressure.

Disadvantages of PEX:
1. It cannot be used outside and can become damaged if even left outside (as are many plastics its very susceptible to ultraviolet) for any long period of time
2. It has a shorter life expectancy and thus does not provide an option to recycle.
3. PEX has an impermeable membrane that may allow the possibility of contaminating your water. Oxygen barrier versions of PEX can be had at additional expense (30% more) to overcome this issue and would be required if you used PEX in radiant floor heating applications
4. Even though it is easier to install it is a more difficult initial installation for the untrained.

Well there it is folks, my take on the PEX controversy. Cheaper, easier to install, less chance of freezing and many more advantages than disadvantages but somehow, to me, just smacks of CHEAP. Is it better than PVC? You bet! Is it better than copper as far as long lasting and known value? No Chance.
Next time and overall discussion of other metallic and plastic options including the perennial favorite PVC.
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