How to join black poly pipe on cottage water systems

Published: June 10, 2020 · Updated: June 11, 2020

black poly pipe water system connected, pieces of black pipe and clamps on white background Photo by Liam Mogan

Learning how to make watertight black poly pipe connections on your water system is a time-saving skill. Instead of waiting for a plumber, you can fix any leaking elbows and tees or a leaking pipe connected to your pump yourself and enjoy running water all weekend long.

Connecting black poly pipe (officially called polyethylene pipe) to pumps and other items involves serrated fittings. At first glance, it seems that all you need to do is slip the pipe over the fitting, install screw clamps, then tighten the clamps. This apparent simplicity hides the fact that you actually need to complete four steps for a watertight connection.

1) Gather what you’ll need
Buy some plumbing-grade pipe sealing compound (henceforth called “goop,” not to be confused with Goop, the universal adhesive) at the hardware store. You don’t always need goop, but it does boost your chances of leak-free success. Grab a propane torch, and a nut driver or a socket wrench for tightening your screw clamps—a screwdriver alone won’t do it. You’ll need two clamps for each joint.

2) Apply the goop
Use your finger to apply some goop to the serrated fitting(s) before the pipe slides on. Hold off on the actual sliding until after the next step.

3) Soften the pipe
Poly pipe is stiff, so soften it with heat to ensure that it seals tightly around your plumbing system’s serrated fittings. Slip two screw clamps over the pipe (stainless steel clamps are best), positioned away from the spot that will be heated. Put on safety glasses, fire up the propane torch, then heat the circumference of the pipe end. Hold the torch a few inches from the surface, and always keep the flame moving as you work. Warm both the outside and the inside of the pipe. In a minute or two, the pipe will have a bit of a glossy look—that’s when it’s soft enough to work with.

4) Position and tighten the clamps
Fix the softened pipe over the gooped up serrated fitting, then immediately slide the screw clamps in position so they’re over the end of the fitting inside the pipe. Use your nut driver or socket wrench to tighten the clamps while the pipe is still soft, then let it cool.

Got an old black poly pipe joint to take apart? Loosen the clamps, and heat the joint to soften it. Once you do that, the pipe will pull off easily.

Pro tip
If poly pipe has split, it means water froze inside.

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