PEX Tubing vs. Copper Pipe - which is better?

A choice of one type of piping over the other has long been a subject of debate between plumbing professionals.
The primary question which must be asked: is the end use a plumbing or heating application?
In closed-loop heating applications, including radiant floor heating, snow melting, baseboard/radiator heating and most others, PEX beats copper in almost every aspect.
However, when dealing with a plumbing project, a multitude of factors arises which make the choice a more difficult one.
We have compiled the most important (in our opinion) of such factors in a table below, which may help you to make a better and a more informed decision. Keep in mind, that despite the fact that we sell PEX tubing, we do not advocate the use of one over the other, but rather believe in a decision where pros and cons have been carefully weighted.

Copper Pipe		PEX Pipe
Advantages	Disadvantages	Advantages	Disadvantages
1. Superior chlorine resistance in typical plumbing conditions. 2. Can be used or stored outdoors, unaffected by sunlight (UV light). 3. It’s fireproof and doesn’t release toxic gas in case of fire. 4. Copper is 100% recyclable. 5. Overall has a good performance history. 6. Has larger ID (inside diameter) than PEX pipes and allows for higher flow rates. 7. Approved by code everywhere. 8. Copper is bacteriostatic (prevents growth of bacteria).	1. Average cost of copper pipes is 4-6 times (300-500%) higher than that of PEX tubing1. 2. Water could have metallic aftertaste if copper corrodes. 3. New copper plumbing systems may require chemical treatment, flushing or washing to remove residual solder and flux from soldering the joints. 4. Copper pipes are high likely to burst when water in the pipes freezes. 5. Requires more copper fittings and connections than PEX tubing because of its rigidity. 6. Possible pinhole leaks, corrosion and leaching of copper2. 7. High likely to be stolen5. 8. Requires basic skills for soldering. 9. More time-consuming to install. 10. Hot water cools quicker in copper pipes.	1. Flexible and requires fewer PEX fittings, which reduces chances of leakage. 2. Inexpensive and requires less labor. 3. Can have long continuous runs without the need for couplings. 4. Is able to expand and contract making it more burst-resistant than rigid copper pipes in freezing temperatures. 5. Has good chemical resistance. 6. Pipes can be bent around most corners without use of elbows. 7. Quieter, reduces "water hammer" effect. 8. Has decades of proven performance6. 9. Reduces scalding7. 10. Easy to install, requires little or no experience.	1. Can’t be used outside or (except underground installations). 2. Non-recyclable. 3. Cracks may form in over-chlorinated or overly-acidic water3. 4. Possible leaching of chemicals4. 5. Can be chewed by rodents. 6. Not approved by code in some localities (such as larger metropolitan areas).

Pros and Cons of Copper Pipes

Copper piping has long been a standard for plumbing across the U.S. and has a good track record in both residential and commercial construction. Copper pipes offer superior chlorine, cut and puncture resistance, allow for higher flow rates and unlike PEX, can be installed outdoor, exposed to the elements. A copper installation has a nicer, more professional finished look and in some applications (i.e. boiler trimming) is much easier to use and more reliable than PEX.

The major downsides of copper are its price, rigidity (requires more fittings) and requirements for specific water conditions, the latter being the most controversial. For instance, a properly chlorinated water is actually best for copper, since it prevents bacterial growth, allowing dissolved oxygen in water to form protective oxide of the pipe walls. High pH water will significantly contribute to formation of mineral deposits, while low pH water will cause corrosion and pitting.
Since copper is thermally conductive, hot water inside the pipes will cool down quicker, which means longer hot water wait times and increased energy bills.
Working with copper requires basic soldering skills and proper equipment and for this reason, may not be the best choice for DIY’ers.

Although copper pipe market has reduced by 50% in the past 10 years (according to "Annual Data 2015, Copper Supply and Consumption 1994-2014" from Copper Development Association, Inc.), it remains a primary choice for plumbing applications across the U.S.

Optimal water conditions: pH between 6.5 - 7.6; chlorine concentration between 2.0 - 5.0 ppm; proper bicarbonate concentration and many other factors.
Best applications: hot/cold water plumbing and hot-water hydronic heating (baseboards, radiators) in both residential and commercial applications.

Pros and Cons of PEX Pipes

PEX has been rapidly growing in popularity in the past years primarily due to high copper prices and increasing popularity of radiant floor heating. It is flexible and therefore requires fewer fittings and allows for longer continuous pipe runs. PEX has an overall good track record and is much cheaper, easier and faster to install than copper. It also is much more resistant to mineral build-up (scale formation) than copper.

The major downside of PEX in plumbing systems is its susceptibility to damage by over-chlorinated water. While PEX-B outperforms the A and C types (exhibits better resistance to chlorine oxidation), all of them are best used in pH-regulated well water applications or areas where tap water has low chlorine content. Water with low pH should be avoided or must be treated prior to coming in contact with PEX pipes (or more specifically, PEX fittings). Water with pH over 7.6 may promote dezincification of brass fittings unless they are made from DZR alloy (all brass PEX crimp fittings sold at PexUniverse are made from DZR brass). We recommend poly PEX fittings for all water with pH above 7.6 or below 6.5

Optimal water conditions: pH > 6.0; chlorine < 4.0 ppm (most important, less is better)
Best applications: residential - hot and cold water plumbing, hydronic/radiant floor heating; commercial – hydronic/radiant heating applications only.

Conclusion

Under normal conditions, both PEX and copper systems are expected to last between 20-50 years. When analyzing the above table, it can be clearly seen that when compared against each other, advantages of copper become the disadvantages of PEX piping and advantages of PEX, in turn, become the disadvantages of copper piping.

With pricing and installation difficulty, as well as other less-important factors aside, water quality is the most important aspect when choosing between PEX and copper. In our opinion, therefore, the choice should be narrowed to the type of piping which will have the longest lifespan at given water conditions – this will both protect the plumbing system from early failure (and costly repairs) and will have the minimal possible environmental impact.

To prevent bacterial growth, it is recommended that water temperatures for both PEX tubing and copper pipe should either be below 77°F (cold water), or above 140°F (hot water);

Environment-wise, while copper is recyclable, the mining and manufacturing process produces huge amounts of pollutants. PEX manufacturing, on the other hand, produces much less waste, but unlike copper, it cannot be recycled at the end of its lifespan.