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FREQUENTLY ASKED QUESTIONS

My 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 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.

What is the outside diameter (OD) of a 1" fitting?
The outside diameter (OD) of a fitting will vary depending on manufacturer and minimum wall thickness requirements for a given size. Plastic fittings are generally specified by a nominal internal diameter (ID). Contact the manufacturer for detailed dimensional information

What is a spigot end?
A spigot end, also known as a street end, is the male end of a fitting having a controlled OD dimension equal to that of the corresponding pipe size.

What is a socket or hub end?
A socket (or hub) is the female end of a fitting having a controlled ID dimension.

What is an interference fit?
An interference fit is the result of the sockets (or hubs) of plastic fittings being tapered. The socket entrance is slightly larger than the pipe OD to allow for easy pipe insertion. The socket bottom is slightly smaller than the pipe OD to ensure that a tight (interference) fit occurs when pipe is inserted. This interference fit is an integral part of producing a strong bond between pipe and fitting during the solvent cementing process.

Can a regular plastic female adapter fitting be used to transition from plastic to metal piping?
No. Plastic female adapters that are all-plastic should never be used as transitions from plastic to metal piping. In fact, you should never use any all-plastic female threaded fitting to transition to or from metal piping. The reason is because of large differences in tensile strengths and rates of thermal expansion/contraction between the two. The proper method to transition between plastic and metal is thru the use of special transition fittings. These special transition fittings are available in a variety of styles and configurations. Check with specific manufacturers on fittings that they recommend for use as transitions from metal to plastic.

Be sure to check local codes concerning acceptable transition practices.

Do I have to use a primer when joining solvent weld fittings?
The answer to this question depends upon the type of material being assembled or possible code requirements. For example, ABS piping material does not incorporate a primer in its assembly process but PVC piping material does. Some codes even require a purple primer be used to easily identify that it has been applied. Most codes allow CPVC CTS systems for domestic hot- and cold-water to be assembled without primer providing the proper type of one-step cement is utilized. Be sure to use primers if it is part of a system’s assembly requirement. For more information contact the specific manufacturer for details or visit the material's respective portion of this website.

Is it acceptable to alter the design of a plastic fitting?
No. Fittings are manufactured to stringent ASTM dimensional requirements. If you come across a need for a special fitting check with your plumbing wholesaler, they will provide you with many application configurations that will more than likely work for your situation. Modifications to a fitting will likely void any manufacturer’s warranty and could lead to part failure.

Can I use compressed air to pressure test a plastic system?
No, unless the procedure being used has been clearly and explicitly approved by the manufacturer(s) of the plastic products or system being tested. Compressed air contains a large amount of stored energy that presents a serious safety hazard should the piping system fail for any reason.

Can I use plastic fittings to build a compressed air piping system?
No. Plastic fittings should not be used to build a compressed air piping system unless they are specifically designed for such service. There are a few manufacturers that produce fittings from a special grade of ABS material that are designed for use in compressed air systems. Plastic pipe and fittings designed for compressed air systems are clearly marked and identified for this type of application. Do not attempt to use common black ABS DWV pipe and fittings for they are not designed for this type of application.

Can I store plastic fittings outside?
Yes, plastic fittings can be stored outside but only if they are covered properly and not exposed to sunlight or extreme weather conditions.

What type of thread sealant should I use on threaded plastic fittings?
You are always safe to use PTFE Teflon tape (3 mil thickness). If a specific fittings manufacturer recommends a specific brand of thread sealant then it is acceptable to use it on their fittings only. There are many different types of thread sealants on the market and even though some may say they are acceptable for use with plastic fittings they may not actually be chemically compatible. Even some Teflon paste sealants can cause premature fitting failure due to chemical attack.

Warning - Always follow the fitting manufacturer’s recommendations on the type and brand of thread sealant to use!

I've heard that too much solvent cement can be as bad as too little cement, is this true?
Yes. Excess solvent cement that is allowed to puddle inside the body of a fitting can be very detrimental and can shorten the life of the fitting. A puddle of solvent cement will “skin over” on its surface as the solvents evaporate. This “skinning over” is analogous to ice on a lake. Just like the ice prevents the water beneath from evaporating so does a “skin” of solvent cement. The difference being that the excess solvent cement beneath the “skin” will continue to soften and damage the wall of the fitting.

Are there ways to prevent excess solvent cement from puddling inside a fitting during the cementing process?
Yes, there are. First, be sure to tip the fitting socket at a downward angle. This will allow excess primer and cement to drip out during the application process. Second, (after applying primer and while the primer is still wet) apply a moderate to heavy coat of cement to the pipe then a lighter coat of cement to the socket and then a second moderate to heavy coat of cement to the pipe again. The two coats of cement on the pipe will ensure that all gaps will be properly filled when the pipe and fitting are assembled. Any excess solvent cement will be forced out of the fitting at the socket entrance instead of being pushed into the inside of the fitting body. Third, always bevel the leading edge of the pipe. This bevel on the pipe removes the sharp leading edge that would otherwise scrape cement from the socket wall producing a puddle of cement inside the fitting.

For additional information on solvent cementing see the respective materials section.

Is it Okay to pre-apply primer the night before?
No. Primer should not be pre-applied the night before you are going to make solvent welds. Once primer dries (evaporates) it is no longer effective. Solvent cement must be applied directly over the surface of wet primer.

Can primer be reapplied on top of dried primer if the process gets interrupted?
Yes. Primer can be reapplied on top of dried primer.

Can solvent cement be reapplied on top of dried cement if the process gets interrupted?
No. Once the solvent cement has dried (evaporated) the surface of the pipe will be slightly larger in diameter and the fitting socket will be slightly smaller in diameter. This will make it difficult if not impossible to insert the pipe and fitting together. This increased interference fit will also place greater tensile stress on the female fitting socket causing possible premature fitting failure (from splitting).

Is there an easy method I can use to tell if I am solvent cementing correctly?
Yes, there is. The best method for checking your solvent cementing skill is to cut open a cemented sample. Use a coupling of the largest diameter you will encounter. After reviewing the “solvent cementing procedures”. Cement a piece of pipe approximately 1” longer than the socket depth into each end of a coupling. Next, using a hand saw, cut the coupling in half (in the same direction as flow). Now, with a screwdriver, carefully pry the pieces of pipe from the pieces of fitting socket. The surfaces should be uniform and dull in appearance indicating that the cement was in full contact with both pipe and fitting wall. If shiny patches are found this indicates an improper bond was made. The most likely cause of which is a lack of cement or the outer edge of the pipe was not beveled.

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