How to install pvc downpiping

PVC is most common form of downpipes installed by the home handyman or ‘DIYer’. Below are intallation instructions for Marley brand downpipes.

You will require a hammer, hacksaw, cloth, ladder or trestles and planks, measuring tape, pencil and rule.

Marley spouting and downpipe can cope with a peak rainfall of 200 mm per hour providing they are correctly installed.

Plan area of roof served by downpipe (in square metres).




0 – 25°



25 – 35°



35 – 45°



45 – 55°



When more than two angles occur in a system the recommended roof area served by a downpipe should be reduced by 5 square metres for each additional spouting angle.


  • Rectangular downpipes should not be used in a horizontal application, or when subjected to head pressure (for example, connected to a water tank).
  • Downpipes should not be used in wall or ceiling cavities.
  • If a round downpipe is being installed horizontally, care should be taken that all joints are sealed.

Downpipe installation.

Assemble downpipe, using angles if there are soffits. Where a downpipe has a socket on it the socket on the long section of the bend can be sawn off. This will enable the remaining spigot to fit into the downpipe socket.

By cutting the socket off the long end of a downpipe bend, a tight offset can be made.

Pipe and fittings should be solvent welded together with Marley MCS Welding Solvent Cement; but do not solvent weld the downpipe socket or top bend to the rainwater head outlet.

The downpipe should be fixed to the wall using three pipe clips per length. By using non-corrosive screws to fix the downpipe clips, the downpipe can be removed in the future.


After installation, Marley downpipes can be painted to any desired colour.

To prepare the surface, wipe down with a bath cleaner, and thoroughly wash. Once dry, apply two coats of acrylic paint ensuring the first coat is dry prior to applying the second coat.


To ensure your new Marley downpipes maintain their good looks for years and years, an annual cleaning using warm soapy water and a car cleaning cloth is all that is required. Simply rinse off with clean water.

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