Tips & Tricks for Working With Plastic Pipe

Safe, sturdy, and cheap, plastic pipe is a standard for water service lines and the DWV (drain‐waste‐vent) system. Traditionally, cast iron, copper, and steel were used in all dwellings and commercial buildings, but in the past 50 years or so, those materials have been replaced by PVC (Polyvinyl Chloride) and its plastic cousins CPVC (Chlorinated PVC) and ABS (Acrylonitrile Butadiene Styrene). The different pipes come in different "schedules", which refers to the thickness of the pipe and how much pressure it will hold.

Uses of Plastic Pipe:

• PVC is used for both water supply and drains — but for water supply piping, only if rated for pressure. In some jurisdictions, it is used for service piping to the building, but not for distribution inside the building. It is never used for hot water. PVC comes in different schedules depending on the application — most common are: schedule 35 for sewer, schedule 40 for water service and DWV, and schedule 80 for high pressure. PVC and ABS used for DWV are also available with a foam core.
• CPVC is used for both water supply and distribution, and if approved by local jurisdictions, and can be used for hot and cold water distribution inside a building. CPVC is available in copper tube size (CTS), schedule 40, and schedule 80 piping.
• ABS is generally used only for DWV.

PVC, CPVC, and ABS pipes are all typically joined using the same methods of solvent cementing, also known as solvent welding. If that sounds a little scary, don't worry: it's safe and easy! If you're about to embark on your own plastic project, we have a few tips to help guarantee your success.

It's worth noting that these pipes could also be joined using mechanical methods such as compression fittings, male‐to‐female adapters, rubber sleeves with clamps, and push‐type fittings (although those methods differ with each pipe and are generally considered not as secure as gluing). Most often these alternative methods are used for repairs and not the initial plumbing.

Before You Begin

• Unless you need to remove a stuck fitting or deal with some other random problem, you'll likely only need the basics to get to work with plastic pipe: cutters/shears for plastic pipe, primer (for PVC and CPVC), and solvent cement ("glue"). And don't forget your towel!
• In the event of a not‐so‐clean cut, you might also need a deburring tool made for plastic (you can also use a file, sandpaper/cloth, or a utility knife). Large diameter pipes are often better cut with a hacksaw, in which case deburring is an absolute must.
• Provided you have a stable surface to set the containers on, you can save time by twisting off the lids for the primer and cement. The lids should have an applicator or "dauber" attached, which you can leave inside the container: instead of having to turn and open the container each use, you can just quickly pull the dauber out. Just remember to close everything up once you're finished!
• You need to work quick when joining plastics, but you also need to be safe. Though you shouldn't actually have to come into direct skin contact with primer or cement (thanks to the dauber), it's a good idea to wear nitrile or other chemically‐resistant gloves. Make sure that the work area is well‐ventilated, and don't work near high heat or open flame.

Watch out! There are many different solvent cements ("glues") out there, so be sure to carefully read the label of what you're getting. PVC, CPVC and ABS each require different cements; they are not interchangeable. There are also transitional cements available for joining different materials, and some cements are specially formulated for cold weather, quick drying times, etc.

Best Practices for Measuring & Cutting Your Pipe

Of course, the necessary first step to gluing pipe together is to cut the pieces to length. In all types of plastic pipe, the piece must be cut square, deburred, and chamfered (or beveled) on the outside edge before gluing. The deburring will allow for a smooth flow of water through the water piping or a smooth flow of waste material through the drainage pipe, while chamfering will allow for easier insertion of the pipe into the fitting and will keep all of the cement from being pushed out of the fitting. (If using a mechanical fitting, the chamfering will keep the gasket or O‐ring from being damaged.)

Now you're probably thinking at this point that you can fit everything together for your sprinkler system or other project so you know exactly how much to cut, make the cuts, then glue everything back together permanently. Seems like a great idea, right? Unfortunately, it doesn't work that way — if you dry fit plastic plumbing connections for the purpose of measuring them, you'll wind up with bad measurements.

Dry pipe will only go part of the way into the fitting — solvent cement (and some twisting) is needed to make the pipe go all the way in, where it butts up against a ridge or lip called the "hub". Take a look inside a plastic fitting and you'll see the hub a little over halfway from the opening. This distance is referred to as the socket depth.

• Plastic fittings are designed to connect to plastic pipe by interference fit, also known as a press fit or friction fit. What this means is that the fitting is designed so that it does not exactly match the pipe — the hub of the fitting is actually tapered a bit to make an extremely snug fit so there are no gaps for glue/cement to fill in.
• Despite the name, glue for plastic pipe is not glue at all. It's actually a solvent that kind of liquefies the plastic, so the pipe and the fitting will essentially melt together. Think of it like welding metal — same idea, but with chemicals instead of a torch. Once the connection has cured, the pipe and fitting are no longer separate pieces, which is what makes a properly cemented connection virtually leak‐proof.
• If you need to know exactly what lengths of pipe you'll need to cut for your project, simply measure from the hub of the fitting to the outer edge to determine the exact socket depth.

Pro Tip: Different manufacturers might have slightly different socket depths, so if you're sourcing your fittings from multiple vendors and need a high degree of precision, you might want to measure each fitting. If you're sourcing all fittings from the same manufacturer, you shouldn't need to check every fitting but we would recommend checking at least one from each different size and type.

Preparing the Pipe & Fittings for Gluing

The preparation for gluing each type of pipe is slightly different. However, ALL must be cleaned to remove any dirt, grease, oil, wax, or any other foreign substance, and ALL must be dry‐fitted.

• You can clean the pipe and fittings using sandpaper or a chemical cleaner. Keep in mind that the cleaner is not a substitute for the primer. The primer begins the chemical reaction of the pipe and fitting so proper bonding may take place. After cleaning, PVC and CPVC are primed and then glued. ABS is glued only; no primer is used.
• To ensure a secure glue joint, the piping and fitting must be dry‐fitted. After the pipe is cleaned and chamfered, insert it into the socket of the fitting to a depth of one‐third to one‐half of the socket.
• If the pipe bottoms out (meaning it goes all the way to the depth of the socket), then the pipe and fitting must be evaluated to determine which is out of tolerance and then start again with a different pipe or a different fitting.

Notes on Primers

Some PVC and CPVC glues have primer included, and some primers have cleaners included. Some glue requires no primer at all (typically used with ABS pipe). Both primer and cement must be applied using all manufactures' safety precautions and procedures to ensure worker safety and a leak‐free joint.

The local jurisdiction should be consulted regarding their specific requirements. If a do‐it‐yourselfer or a professional plumber uses a product that doesn't require primer on a PVC or CPVC pipe, they could be in for a major re‐pipe if an inspector deems that the primer was required but wasn't used.

Primers come in either purple or clear color. Some jurisdictions require that the primer be purple, and that the color is visible during inspection. If clear primer is allowed, the plumber should have a can of the primer on the job site for the inspector to evaluate.

How to Connect the Pipe & Fittings

The actual process by which you join PVC/CPVC/ABS pipe and fittings is called "solvent welding". It's a fairly simple procedure — you just need to move quickly, and try not to make a mess!

Step 1: Always make sure that your cuts are square and free of burrs before you start applying primer and cement, even when using a tubing cutter. Uneven cuts and stray bits of plastic make for weak welds and can lead to issues at the joint down the road. Pipe should be dry and free of dirt and debris, as well.

Step 2: Be sure the glue and primer have not expired. Most cleaners, primers, and glue have a three-year shelf life; CPVC glue has a two‐year shelf life. The date of manufacture is stamped on the can. The cement should be fluid, not thick like jelly would be.

Step 3: For PVC & CPVC ONLY (ABS does not use primer) — Apply primer to both the inside of the fitting and on the pipe exterior, starting with the fitting. You'll want to coat each to the socket depth. Don't be stingy, but don't use so much that it puddles or runs excessively. Hold the fitting or pipe so that should the primer drip, it drips down and out of the fitting/pipe, not further inward.

Step 4: When you're done putting the primer on, move quickly to apply the cement to the fitting and pipe while the primer is still wet. (The primer sometimes looks dry, but it will still be wet if the joint is made within five minutes. This is the timeframe when the chemicals in the primer are evaporating.) Spread a generous, even layer of cement directly over the primered areas.

Step 5: Insert the pipe into the fitting while slowly twisting it a quarter‐turn. This will spread the cement and create a stronger weld. A bead of cement should form around the entirety of the new joint, with excess cement being pushed out.

Pro Tip: If the orientation of the fitting matters — like with an elbow or tee — insert the pipe with the fitting a quarter‐turn away from its final position. This way the fitting will align perfectly when you turn it to spread the cement.

Step 6: Firmly hold the new connection together for 30 seconds to keep everything in place as the solvent does its thing. After 30 seconds, the two pieces of plastic will have "melted" together sufficiently to be left alone to fully cure. Gently wipe off any excess cement and primer immediately after the 30 seconds; leaving it on could damage the pipe.

Step 7: Consult the cement manufacturer's instructions for curing times. Most will require at least two hours before the connection can be put into operation.

Joining Plastic to Other Materials

PVC and CPVC pipes may be joined to each other and to other piping materials such as copper and PEX. This can be done with the use of male and female adapters. If using this method and one of the adapters is metal, it is recommended that the plastic side of the joint be the male side. If you apply a metal male adapter to a plastic female adapter, then the female fitting will be stressed and could break and require replacement.

PVC and CPVC both can be joined with compression couplings and push fittings. Manufacturers' recommendations for assembly and restrictions regarding location (i.e., inside or outside buildings) should be strictly followed.

PVC and ABS DWV piping may be joined to cast iron, DWV copper, and galvanized vent piping using flexible couplings. The couplings for the type of materials that may be joined will be stamped on the fittings. Some are shielded with a band all around and multi‐clamped to ensure a stable transition. Plastic piping may be joined to dissimilar metal fittings using a push‐type gasket that is inserted into a cast iron fitting.

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