Can PVC pipe be exposed to the sun?
PVC does not readily degrade when exposed to sunlight (ultraviolet radiation) due to natural UV inhibitors present in the material. Short-term exposure to sunlight, such as during construction, is typically not a problem for PVC pipe. PVC piping may be used in outodoor applications when the piping system is painted with a light-colored water based acrylic or latex paint that is chemically compatible with PVC. When painted, the effects of UV exposure are significantly reduced.

Can insulated plastic piping meet the 25/50 requirement?

Plastic Piping in Return Air Plenums by R. C. Wilging – PE

Summary:Because plastic materials do not qualify as non-combustibles their use in air handling plenums has been an issue for years. The code provisions that cover this subject clearly refer to “exposed” materials. Questions about whether insulated plastic piping would meet the 25/50 limits have now been answered in the affirmative by ASTM E 84 tests of 4″ and 6″ PVC and ABS pipe with solid wall and with cellular core wall. To read the full response to this question, click here.

How does PVC pipe behave at different temperatures?
PVC pipe exhibits decreasing pressure rating and stiffness with increasing temperature.  As with dimensions, the pressure ratings and published pipe stiffness figures for PVC pipe are listed at an operating temperature of 73F.  To determine the pressure ratings and stiffness of PVC pipe at higher temperatures, multiply the pressure rating or pressure class and the stiffness / deflection by the pipes de-rating factors at that temperature.  An example of a table of PVC pipe de-rating factors is shown below. Consult with the manufacturer of your pipe for specific data. The typical upper limit for continuous use of PVC pipe is 140 F.

As an example, using the table above, a PVC pipe rated at 450 psi at 73 F, used at 100 F would have a pressure rating of:

450 psi x 0.75 = 337 psi

Does PVC pipe have a long life expectancy?
Yes, studies on PVC pipe made in Europe in the 1930’s and been in continuous use suggest a very long useful life for these products of a hundred years or more, which will generally exceed the lifespan of the structures they are installed in.

Can PVC piping products be recycled?
Yes they can. Since PVC pipe products have very long useful lives, not much pipe is currently available for recycling as it is still in use. While current standards do not generally allow for the practice of recycling used pipes into new certified pipes.  PVC pipe producers can recycle nearly all production scrap in-house. Since PVC is a thermoplastic PVC pipe can simply be reground, pulverized and returned to the extrusion process to make new pipe.

Why do I need to use primer on a PVC solvent welded joints?
Primer is a mixture of solvents, similar to those found in the cement and is used to soften or “prime” the pipe and fitting prior to adding cement. Use of primer may be required by code in your area. Visit our cements page for more information on solvent cementing.

What is the best way to repair a leaking PVC solvent weld joint?
Whenever possible, cut out the leaking joint and start over.  A leaking solvent welded joint is an indication that the joint was not made correctly. It may not have been fully bottomed, a component may have been damaged or foreign materials may be trapped inside the joint. For a temporary repair, plastic fillet hot air welding can be used on the outside of the pipe and fitting to stop very minor leaks. This should only be used as a short term measure before the joint can be replaced.

Does long term exposure to sunlight degrade exposed PVC pipes?
PVC pipe contains stabilizers to protect the pipe against attack by UV present in sunlight. After several months of outdoor exposure a discoloration may appear on the surface of the pipe, however, the performance of the pipe is not affected.  After two years of exposure, there is only a slight reduction in the impact resistance of the material. PVC pipe used in permanent outdoor exposures should be protected by a light colored compatible water based paint. Do not use oil based paints.

Is PVC pipe easier to install than alternative materials?
PVC pipe is a light weight yet strong material when compared to many alternatives.  A length of PVC pipe will weigh 1/5 th of an equivalent size section of cast iron pipe making it easier to install. This product is easily assembled in solvent-welded or gasketed versions that are both intended to be leak free, once properly assembled.

How does PVC pipe behave when exposed to fire?
PVC pipe, while combustible, does not continue to burn once a flame source is removed. A main cause of fire fatalities is exposure to carbon monoxide, which is produced from common materials and products like wood, furniture, carpet, and fabrics.  It is estimated that plastic pipe systems represent less than 1% of the mass of all combustible products in a building.  The majority of piping is also installed behind non-combustible materials such as gypsum wall board

Is PVC pipe permitted for use in high-rise buildings?
While local or state codes do vary in a few areas and have restrictions for plastic pipes, model codes allow for PVC DWV systems in high rise structures when firestopping methods are used to restore penetrations to original values. Firestopping in UPC chapter 15, for example, is required for both plastic and metal systems. To determine if there are any restrictions in your area, consult your codes.

My PVC fittings have a visible line in them, are they cracked?
No. The noticeable line you are seeing is a more than likely not a crack. If you are unable to open it up by pulling on the part, then what you are seeing is most likely a knit-line (other names include weld-line and flow-line). The formation of a knit-line is an intrinsic part of the injection-molding process and is created when hot melted plastic flows under pressure into a mold cavity, around cores and finally “knits” back together on the opposite side of the cavity fill point. Knit-lines will sometimes appear straight or as gently wavy curving lines running the length of the fitting (both inside and outside). A fitting that displays this type of line is not defective. A knit-line will not impact the integrity of the product or system.

Is the straight, slightly raised line on a PVC fitting a defect?
No. This slightly raised line is where the parting line of the mold is located and is not a defect of the fitting. The parting line is the location of where the two halves of the mold separate to allow part removal.