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A Plumber’s Guide to Connecting Plastic Pipes and Fittings


Over the years, studies have shown the limitations of the old metal pipes used in plumbing. That has paved the way for plastic manufacturing which is said to be the future of plumbing.

Yet while plastic pipes are mainstream, the major problem that most people have with them is how to connect them to fittings.

In this article, you will learn how to connect plastic pipes and fittings as well as some basic plumbing tips.

How To Connect Plastic Pipes and Fittings

The process by which you join PVC, CPVC or even HDPE pipes and fittings is called “solvent welding”.

The procedure is quite simple. Here are a few steps on how to do it:

  • Step 1: Before you start applying the primer and adhesive, always make sure your cuts are square and burr-free, even if you are using a pipe cutter. The catch is that uneven cuts and misplaced pieces of plastic weaken welds and lead to joint problems. Therefore, pipes should be dry and free of dirt and debris.
  • Step 2: Now check that the primer and adhesive have not expired. Most primers and glues have a shelf life of three years. Chlorinated polyvinyl chloride (CPVC) glue, on the other hand, has a shelf life of two years.
  • Step 3: This applies to PVC and CPVC pipes only because no primer is used in acrylonitrile butadiene styrene (ABS) pipes. Apply the primer to the inside of the fitting and outside of the pipe, starting with the fitting. You should apply a primer to each fitting to the depth of the socket. Apply the primer moderately to avoid puddles or excessive dripping. Hold the fitting or pipe so that if the primer drips, it will have to drip down and out of the fitting, not in.
  • Step 4: Once you are finished with Step 3, quickly apply cement to the fitting and pipe while the primer is still wet. Do this often within 5 minutes of using the primer, as the primer will evaporate if you dawdle.
  • Step 5: Here, the pipe will be inserted into the fitting by slowly turning it a quarter turn. That will spread the cement and create a stronger weld. You will notice a bead of glue has formed around the whole of the new joint and that the excess has been pushed outwards.
  • Step 6: To keep everything in place while the solvent does its job, you must hold the new joint firmly for 30 seconds. At the end of this time frame, the two plastic pieces will have “melted” enough to be left in place and harden completely. Next, gently wipe off any excess cement and primer; otherwise, it could damage the pipe.
  • Step 7: Refer to cement manufacturer’s instructions for curing times. In most cases, it will take at least two hours before the fitting can be put into service.

7 Plastic Plumbing Tips for a Better Plumbing System

Now that you know how to connect plastic pipes and fittings, it’s time to learn a few tips to improve your plumbing experience.

Take precautions when gluing in corners.

In many cases, as you try to make connections, you will find that there are pipes that move and pipes that don’t. If you start gluing fittings arbitrarily, you may find yourself in a situation where you can’t fix the last fitting.

Keep in mind that the last fitting to be glued should be that of a pipe with a small amount of leeway. This is usually where a vertical pipe meets a horizontal one so that you can lean on an elbow or tee from two directions.

Reuse landlocked fitting

If you need to replace pipes, but it is difficult to change the fitting, the old fitting can be reamed and reused.

Picture this: A tee comes out of the back of a cupboard, and a broken pipe leads to it. Or the tee is so deep in the floor joists that you can’t reach it. In these cases, the golden rule is to cut the pipe near the joint, then use a Socket Saver to ream the pipe to expose the inside of the fitting. Thereafter, cement a new pipe into the old fitting and reuse it.

Deburr for leak-free connections.

Burr remnants at the end of a pipe create channels in the wall when you push the fitting onto the pipe. This gives way to small holes that will result in leaks or an inability to withstand the pressure. It is therefore advisable to always scrape off any burrs with a utility knife before assembling the pipes.

Avoid callbacks – use straps.

Temperature changes often lead to changes in the length of plastic pipes. When you hang a pipe from a plastic J-hook, you will hear a ticking sound when the pipe slips past the hook.

When this happens, don’t panic because these are not ticks of water drops from a leaking pipe. So instead of J-hooks, use plastic straps instead.

Apply the elbow rule.

For pipes less than 3 inches, there are three types of 90-degree elbows: short sweep, vented, and long sweep. You can quickly identify the vent elbows by paying more attention to their significant curvature. Remember that these curves can only be used on a venting path that carries air, not water.

The basic rules when you want to use the other two types of bends are as follows:

  • If the water accelerates by turning the corner, usually from horizontal to vertical, use a short sweep.
  • If the water slows down, usually from vertical to horizontal, use a long sweep.

Support hot drain lines

Generally, pipes that regularly drain water under high temperatures need continuous support. Often these are the pipes under sinks that are connected to dishwashers that collapse between the ordinary supports. In this case, experts recommend that you slide a larger pipe over the drain line before attaching fittings and then secure the supports.

Use tubing cutters for small pipes.

For pipes up to 2 inches, use a pipe cutter that is a larger version of the type used for copper pipe. It allows a perfectly straight cut, with no burrs or chips to clean. Most importantly, it does not take up much space in the tool bucket.

Using plastic pipes for plumbing takes real expertise. Sometimes you may cut the fittings disproportionately, and other times you may not glue them properly. Either way, by sticking to the tips given above, you will get there–ensuring safe and efficient access to water for the house’s inhabitants.

Andrew Mcaffrey