How to Install a Plastic Waste Pipe

Written by robert ferguson
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How to Install a Plastic Waste Pipe
An example of metal p-trap (Jupiterimages/ Images)

There are many types and sizes of plastic waste pipes to choose from and they are not always interchangeable. It is important when extending or adapting an existing plastic waste set-up to purchase the same size and type. If adapting to a different type or size of drainpipe, like cast iron or galvanised steel, purchase the applicable adaptors suitable for the changeover point. The standard waste pipe connects using 1 1/2-inch plastic washers and nuts. Most waste pipes connect to larger 2-inch PVC drainpipes that stub out of the wall or floor on one end and a 1 1/2-inch plastic p- trap on the other.

Skill level:
Moderately Easy

Things you need

  • PVC trap adaptor
  • PVC cleaner and cement
  • 1 1/2-inch washers and nuts
  • Plastic waste pipe
  • Adjustable Pliers

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  1. 1

    Connect the applicable-sized PVC trap adaptor to the drainpipe by first cleaning both the drainpipe and the trap adaptor with PVC cleaner and then adhering with PVC cement. The trap adaptor is a threaded fitting used to connect the waste pipe to the drainpipe.

  2. 2

    Connect the plastic waste pipe to the p-trap. Use a plastic nut to connect the waste pipe to the short end of the p-trap. The bevelled end of the waste pipe seals the connection, eliminating the use of a plastic washer. Do not over tighten to allow for adjustment.

  3. 3

    Connect the opposite end of the pipe to the trap adaptor using a 1 1/2-inch plastic washer and nut. Slide the nut onto the waste pipe followed by the plastic washer. Position the washer so that it tapers toward the trap adaptor.

  4. 4

    Insert the waste pipe into the open end of the trap adaptor. Adjust the waste pipe to the desired position, thread the nut onto the trap adaptor and tighten until snug.

  5. 5

    Tighten all fittings by hand until snug and check for leaks. If a leak appears, use adjustable pliers to tighten.

Tips and warnings

  • Lay newspaper under pipes to help identify leaks.
  • Use a small pan when disconnecting plumbing to catch any water.
  • Keep an eye on repaired pipes for a few days to ensure nothing is leaking that could damage cabinets and flooring.

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