pex with brass coupling vs. cpvc

coffeehausJuly 3, 2008

Our contractor wants to know if we want PEX with brass coupling/elbows or CPVC in our new house. We have well water which is fairly acidic in our area of central VA, although we will be installing a neutralizer. What are the pros/cons on these materials?


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What is PEX?

PEX is cross-linked polyethylene. Through one of several processes, links between polyethylene molecules are formed to create bridges (thus the term "cross-linked). This resulting material is more durable under temperature extremes, chemical attack, and better resists creep deformation, making PEX an excellent material for hot water and other applications.

How long has PEX been used?

PEX was developed in the 1960s. PEX tubing has been in use in many European countries for plumbing, radiant heating and snow melt applications since that time. PEX was introduced in the United States in the 1980s, and has seen significant growth in market demand and production.

What are recommended uses for PEX?

PEX 's flexibility and strength at temperatures ranging from below freezing up to 200 degrees Fahrenheit makes it an ideal piping material for hot and cold water plumbing systems, service lines, hydronic radiant heating systems, snow melting applications, ice rinks and refrigeration warehouses.

Why is PEX an excellent piping material for plumbing?

PEX is ideally suited for potable water plumbing applications. It is flexible, making it easy to install and service. PEX is able to withstand the high and low temperatures found in plumbing and heating applications, and is highly resistant to chemicals found in the plumbing environment.
Flexible systems are quieter than rigid piping. The smooth interior will not corrode which can affect other materials long term pipe flow characteristics. PEX is also very freeze- break resistant. PEX systems have fewer joints and are easier to install providing a lower cost installation over traditional plumbing materials.

How can I be sure that PEX is a safe product for plumbing?

PEX is manufactured and tested according to stringent national consensus standards: ASTM F 876, F 877, AWWA C904 and CSA B137.5. Both the product manufacturer and independent third party testing agencies conduct routine quality control and quality assurance evaluations to insure the product meets ASTM, ANSI/NSF International and CSA Standards. Compliance with the standards ensures the end user of safety and quality. Additionally, PEX is included in all of the major model plumbing codes used in the United States and Canada; NPC, UPC, IPC and NSPC, and approved by HUD for hot and cold potable water plumbing use.

Where is PEX approved for use?

PEX is an approved material in all the current model-plumbing codes; however, some jurisdictions using older versions of these codes may not have amended the code to include PEX tubing. Contact the local authority with jurisdiction over plumbing to verify the acceptance of PEX tubing for plumbing applications in your area.

Can PEX be used under the slab?

Yes. The flexibility of PEX allows it to be supplied in coils meaning installations under the slab can be made in a single, continuous length without the need for fittings. PEX is not affected by concrete, (it is commonly encased in concrete for radiant floor heating). PEX, however, must be sleeved when penetrating a slab.

Can PEX be used for underground cold-water service applications?

Yes. Although the high temperature resistance of PEX makes it particularly suitable for hot and cold interior plumbing applications, it also makes an excellent underground water service piping. The new AWWA C904 standard also applies to PEX used in this application. PEX can be installed using the same fittings recommended for copper tube sized SDR-9 polyethylene tubing.

Can PEX be used for aboveground outdoor applications?

No. PEX is currently designed for indoor and buried applications only and is not recommended for outdoor, aboveground use. Short exposures to sunlight during construction are permissible, but should not exceed the manufacturers recommendations. PEX should be stored under cover, shielded from direct sunlight or in the original packaging. In the future, PEX products rated for outdoor use may be developed.

Can PEX save me money?

Yes. PEX saves money in many ways. For the installer, PEX tubing is competitively priced. Installation of flexible systems is fast because of the easy handling of the tubing and PEX installation requires fewer directional fittings. Since most plumbing problems occur at joints, fewer fittings also reduce the chances for leaks and callbacks, saving the installer even more time. The homeowner saves in the cost of the installed system, and can reduce utility costs in some layouts .

Home run or manifold plumbing systems utilizing PEX tubing can substantially reduce water and energy consumption in a home. The home-run concept provides dedicated direct lines from the manifold to the fixtures, reducing the amount of water that must be purged from the lines to get hot water at the fixture. Direct lines can be sized to the fixture requirements, further reducing the amount of time to wait for hot water. Faster hot water delivery reduces water waste and the amount of times the water heater must cycle to supply hot water.

What is the expected performance of PEX water distribution systems?

PEX is designed and tested to perform as well or better than any other material approved for hot and cold-water distribution systems. For indoor plumbing applications, PEX is expected to perform as long as copper, CPVC or any other approved plumbing distribution materials.

What joining systems are available?

There are several methods of connecting PEX, all of which involve mechanical fittings. There are two approved standard specifications for PEX connections: ASTM F 1807 and ASTM F 1960. Both reference mechanical insert fittings. The crimp fittings specified in ASTM F1807 are the most widely used. Other fitting systems, including insert and outside diameter compression fittings, are also available. PEX cannot be joined by solvent cement or heat fusion methods.

What manufacturing methods for PEX are available?

There are currently three methods for producing PEX tubing, the "Engle" or "Peroxide" (PEX-A) method, the "Silane" (PEX-B) method, and the "E-beam" (PEX-C) method . All three processes produce tubing that exceed the minimum requirements of ASTM F 876 and are acceptable for potable water distribution applications. All PEX that has been tested and certified for potable applications carries the mark(s) of nationally recognized third-party certification agencies such as NSF, IAPMO, ICBO-ES, Warnock Hersey or UL.

How long can PEX be exposed to sunlight?

PEX tubing is not intended for outdoor applications and must be stored in a covered environment not exposed to direct sunlight. Refer to manufacturerÂs instructions as to how long your pipe can have UV or sunlight exposure.

What are temperature limitations for PEX?

PEX tubing can be used up to 200° Fahrenheit for heating applications. For plumbing, PEX is limited to 180° F. Temperature limitations are always noted on the print line of the PEX tubing.. PEX systems are tested to and can be used with standard T and P relief valves that operate at 210" F and 150 psi.

How are PEX systems tested for leaks?

PEX plumbing and radiant heating systems can be pressure tested using water to check for leaks. Follow manufacturer's instructions.

How soon after installation can you pressure test a PEX tubing installation?

Most PEX plumbing systems can be tested immediately after the installation is complete but follow manufacturerÂs directions.. There is no wait time for glue to dry or joint to cool off. Manufacturer's instructions should be followed in cold climates.

Where is PEX available?

PEX is available through most plumbing wholesale distributors throughout the United States and Canada. Many retail building supply outlets also supply PEX piping and fittings. Piping and fittings are commonly available in 1/4" through 1" CTS (Copper Tube Size) with some manufacturers also supplying larger sizes up to 2." Because the wall-thickness is proportionate for each size, the pressure ratings are the same for all sizes.

What sizes, lengths and packaging options of PEX are available?

PEX is available in 1/4" through 1" CTS (Copper Tube Size) and is packaged in coils or 20' straight lengths. Some manufacturers tubing is color-coded for easy identification of hot and cold lines. Coil lengths generally run to a maximum of 1000' and are available in a variety of shorter lengths.

Is flexible PEX plumbed differently than rigid material plumbing systems?

Yes, the flexibility of PEX allows many directional changes to be made without fittings. PEX systems are sized in the same manner as copper or CPVC CTS plumbing systems. PEX piping is also used in high performance manifold plumbing systems that takes advantage of the flexibility and cost effective.

What are manifold plumbing systems?

Manifold, parallel or home-run plumbing systems are much like a breaker box for the electrical system in the home. The manifold provides a common location from which all the plumbing fixtures are supplied. Some high-end manifolds also feature fixture shut-off valves allowing the user to shut off the water to individual fixtures from one location. Others are semi-home run manifolds or termination manifolds, which may feed the plumbing requirements for a room or set of rooms and reduce the number of fittings required in the plumbing system.

How are PEX systems sized?

PEX systems are sized just like other CTS plumbing materials such as copper or CPVC when used in a trunk-and-branch installation. PEX can be sized in manifold systems to meet the specific demands of each fixture, reducing water and energy waste in the home.

Is the thermal expansion/contraction of PEX a problem?

No. While PEX expands more than other plumbing materials, directional changes made with the tubing and some slack in the tubing during installation accommodate the expansion and contraction of the system if properly installed.

Is PEX freeze-break resistant?

PEX piping is freeze damage resistant and can expand and contract as water freezes and thaws within the tubing. No tubing material is freeze-break proof, however, and PEX should be installed using the same locally-prescribed insulation requirements to prevent freezing of any plumbing system.

How do I thaw PEX lines?

When water freezes inside PEX tubing, it can be thawed using a hair dryer, warm wet rags or heat tape, taking care not to overheat the tubing beyond the maximum recommended temperature.

Can PEX be joined with solvent cement?

No. PEX cannot be joined with solvent cement, glues or heat fusion. PEX is installed using only mechanical fittings or compression fittings.

Where can I use CPVC?

Copper tube size (CTS) CPVC is designed for use in hot-and-cold-water distribution systems. CPVC systems are ideal for all potable water piping requirements in typical residential (single and multi-family), motel/hotel, mobile home, manufactured housing, light commercial, and institutional structures.

CPVC systems conforming to ASTM D2846 are rated for continuous service at 100 psi and 180 degrees F and are marked accordingly. The model codes recognize CPVC's capability to handle short-term pressure/temperature excursions beyond these levels. Therefore, CPVC is well suited for usage as T/P relief valve discharge lines, evidenced by its faultless service history over the past two decades in this application.

Iron pipe size (IPS) Schedule 40 and Schedule 80 are used for a wide variety of industrial applications.

What about CPVC's cost relative to other materials?

CPVC is a very cost-effective system. The basic molecular building blocks of the CPVC molecule are chlorine, derived from salt, and ethylene, which comes from oil or natural gas. Because 2/3 of the CPVC molecule is derived from common salt, less energy content goes into making one foot of CPVC pipe than any alternative material. The price of CPVC should remain more stable than other materials in the future.

What is the expected performance of a CPVC water distribution system?

CPVC piping systems have been installed and operated since 1959, and initial installations are still performing faultlessly. CPVC piping will not fail prematurely due to corrosion, electrolysis, or scale build-up in areas where water, soil, and/or atmospheric conditions are aggressive.

What about product availability?

CPVC pipe and fittings are available in 1/2 through 2 inch CTS (Copper Tube Size O.D.). A full range of fittings exists in all sizes. Specialty components including transition connections and chromed supply stops with CPVC solvent weld inserts have been introduced recently. Additional complementary components will naturally evolve (i.e. shower mixing valves and gate valve adapters). In applications calling for larger lines, CPVC is available in IPS sizes (sch. 40 and 80) up to 12" diameter. Transitions from CTS to IPS products can be accomplished in several easy ways.

Will CPVC save me money?

Yes. CPVC can be installed at least 25% more quickly than copper or iron systems. Financial savings are also realized with regard to lower tool costs and insurance advantages. Considering the frequent rise and fall of the copper price structure, CPVC offers a continuing material cost advantage, often as much as a full 30% savings.

Will a CPVC system offer a financial advantage to Owners in terms of utilities expense?

Yes. The thermal conductivity of a copper system is 2500 times that of a CPVC system. The improved insulating characteristics associated with CPVC can generate substantial long-term savings for an energy conscious home-owner or tenant. CPVC will keep hot water hot for a much longer period of time than copper tubing.

How should I size the lines in a CPVC system?

A CTS CPVC system will use the same size pipe that a copper system would, providing a full bore flow system. In general an IPS CPVC system will use the same size pipe as an iron system.

What is the thermal expansion rate for CPVC, and how can I best allow for expansion and contraction when installing?

CPVC piping will expand about 4 inches per 100 feet with a 100 degree F temperature change. The fact that CPVC has higher thermal expansion than metals has led to some concern. However, laboratory testing and installation experience have demonstrated that the problems are much smaller than the coefficient of thermal expansion would suggest. The stresses developed in CPVC pipe are generally much smaller than those developed in metal pipe for equal temperature changes because of the difference in elastic modulus.

Should special considerations be taken to connect CPVC to a hot water heater?

In some instances, yes. However, these considerations are based on concerns regarding external sources of heat. The hot water from the heater will not affect the CPVC.

When connecting to a gas water hear, CPVC should not be located within 6" of the heater's flue, if the flue has no insulation. A metal nipple or flexible appliance connector should be used. This measure eliminates the potential for damage to plastic piping that might result from excessive radiant heat from the flue. If the flue is insulated, the instructions of the flue manufacturer should be followed.

How can I use CPVC if I run under slab?

When using CPVC with joints under slab, YOU MUST PRESSURE TEST THE SYSTEM BEFORE POURING THE SLAB. Also, it is wise to use 1" foam insulation pipe sleeve at changes in direction, where the pipe comes out of the slab, and at construction joints. The pipe should be evenly supported in smooth bottom trenches. The backfill should be free of rocks and debris.

The purpose of the foam insulation is to:

Provide for a degree of movement at changes in direction due to thermal expansion.
Protect the tubing from shear forces due to minor shifts in the slab at construction joints.
Provide some protection from abuse during the construction phase for the pipe where it emerges from the slab. Longer lengths of pipe (rolled pipe) is also available for under slab installation. Follow the instructions of the manufacturer.
What method should I use to thaw a CPVC line?

If the frozen section of pipe is accessible, wrap it with a cloth saturated with hot water. Keep the cloth hot by re-dipping in hot water as necessary. Be careful not to burn your hands. A second technique that is quite successful is to blow heated air directly on the area where the freeze occurred using a low wattage heater/blower such as a hair dryer. Obviously, prevention is the best way to address frozen pipe problems.

Must I use plastic insulators wherever CPVC passes through a stud?

Technically, no such provision need be made when passing through wood studs. When passing through metal studs, some form of protection must be used to protect the pipe from abrasion and to prevent noise. This protection may come from plastic insulators, rubber grommets, pipe insulation, or similar devices.

Should I use metal nipples on a CPVC system when I come through the sheetrock?

In areas where there is a likelihood that stresses or impact abuse will occur, a metal nipple is recommended. Such applications as tub fillers, showerheads, and outside sillcocks are examples. However, CPVC stub-outs for closets, lavatories, and sinks are appropriate.

Should I use pipe dope, Teflon® tape, or Teflon® paste with CPVC threaded adapters?

Teflon® tape is always safe and effective with CPVC. If you wish to use a paste or pipe dope, always check with the manufacturer for a recommendation because some pastes or dopes contain solvents that may be incompatible with CPVC.

Should specific types of primers and solvent cements be used on a CPVC system? Are specific colors required?

CPVC solvent cement should always be for CPVC piping and manufactured to meet the requirements of ATM F 493. Purple primer manufactured for PVC pipe is acceptable. Faster flashing CPVC primer is available, and is recommended for cold weather installations. Orange CPVC solvent cement and purple primer are specifically required by certain code bodies to facilitate identification by plumbing inspectors. Unpigmented CPVC solvent cement and primers are available and are acceptable in various jurisdictions. Clear cement/primer provides neater finished appearance. One-step cements are now available and are fully satisfactory if the manufacturer's instructions are carefully followed. Your local plumbing inspector can provide a final answer to this question.

How long can CPVC systems be exposed to sunlight?

CPVC can easily withstand the ultraviolet exposure commonly experienced during the construction phase of a project, provided on-site inventories are turned regularly as would be anticipated. If CPVC is used in above-ground, outdoor applications, protection from ultraviolet attack can be achieved by shielding or by painting the system with an exterior-grade latex paint.

What are the preferred methods of cutting CPVC pipe?

A benefit of CPVC pipe is that numerous, inexpensive choices of cutting tools are available to the installer. CPVC piping has for years been cut by fine-tooth saws. The preferred method is the circular tubing cutter, modified with a plastic cutting blade. This cutter assures a square, clean cut each time and is extermely efficient in terms of labor.

An alternative method is the ratchet cutter. Although this option is quick and easy, the pressure created while cutting the pipe could cause cracking of the pipe wall. This problem is of prime concern during cooler weather (50 degrees F or lower). For this reason, ratchet cutters should be considered only during the summer months. Keep the cutting edges of the cutter sharpened.

Several power tools have been used on major job sites where larger diameter pipe is being installed. Circular saws and portable grinders with abrasive cutting discs are two of the numerous methods being employed by contractors.

I have been told that CPVC pipe can split during installation. Why would this occur? How can these cracks be prevented?

Most cracks are initiated by rough handling. This handling can occur during shipment, while being inventoried at the wholesaler, or while on the job site. Also, fine cracks can be caused by cutting the pipe with dull or damaged ratchet cutters, or by using ratchet cutters in lower temperatures.

The vast majority of cracks occur during colder weather months. When ambient temperatures are below 50 degrees F, CPVC should be handled more carefully.

To reduce problems resulting from cracked product, several measures can be initiated:

Educate your installers. Make them aware of the potential problem and instruct them to handle CPVC in an appropriate way.
Use a saw or a circular tubing cutter with a plastic cutting blade (Rigid #151P or similar) to cut pipe to length.
Inspect pipe ends thoroughly prior to making a joint. Should a crack be evident, cut off any split portion before proceeding.
During cold weather, gripping the tubing tightly around the area to be cut for about 10 seconds prior to making the cut will warm the tubing and reduce possible problems.
Are there insurance advantages associated with CPVC systems?

Yes, most definitely. Insurance cost reductions result from several factors:

Absence of the torch during construction.
Significant reduction in injuries, particularly burns, can translate to reduced workmen's compensation costs.
Reduced job site theft loss.
Is CPVC a factor in reducing noise associated with the movement of water?

Yes, CPVC is extremely quiet due to the polymeric structure of the product. CPVC systems are virtually silent. Also, noise associated with water hammer is all but eliminated.

Are there other benefits associated with the polymeric makeup of CPVC systems?

Yes. Due to the CPVC polymeric structure, costly condensation concerns are eliminated, further reducing the long-term problems that one expects with a metal installation. Also, CPVC offers a potable water distribution system that eliminates the metallic taste and potential health hazards associated with metal systems.

What about health, safety, and fire toxicity issues?

Metal piping interests have initiated many attacks on plastic systems, under the guise of health and safety issues. Tests performed at respected universities and independent laboratories confirm that CPVC is superior to copper/lead solder systems in terms of water quality effects and is "no more toxic than wood" in a fire.

All plastics used in potable water systems must be tested regularly and certified by a similar third party certifier as meeting the strict public health requirements of ANSI/NSF 61. This testing ensures that drinking water carried by plastic pipe meets all EPA standards.

    Bookmark   July 6, 2008 at 6:56PM
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Can someone give me an idea of the difference in cost between installing all copper vs. a pex with brass coupling installation in a 4000 sq. ft. house on 3 levels with 4.5 baths?

    Bookmark   August 1, 2008 at 3:31PM
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I know pex goes for about $35 for 100 ft. roll, copper pipe can't get near that!

    Bookmark   April 22, 2009 at 11:03PM
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That depends on the type of install, it can be just as much or more than copper, especially with a "home run system" which is individual circuts run back to a valved manifold, offering water savings, minimal pressure drops when other fixtures are used and easy isolation of individual circuts (Kind of like how we wire our houses, not all on one breaker)

    Bookmark   April 22, 2009 at 11:10PM
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wow. thanks for the low down on pex. My plumber used it for my new faucet/sink and I was curious how it compared to copper & CPVC. I like the info on freezing since that is always a concern of mine here in the North East.

    Bookmark   April 28, 2009 at 12:50PM
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