Leaking joints in plastics

Leaks from plastics guttering can be just as damaging as those from cast-iron and should be attended to as soon as possible.

In most plastics guttering systems, the sections are connected by union clips, lined with replaceable rubber seals. In some cases, the seal is positioned in the end of one section of gutter with a separate clip used to secure the joint. When the clips are sprung home, the gutter ends compress against the pad to form a watertight joint – but this can leak if silt finds its way in.

To replace a seal, undo the clip holding the ends together, lift out the old seal and thoroughly clean the surfaces which come into contact with it. Fit a new seal of the same type and clip the joint back together by squeezing the ends of the gutter slightly and snapping the union clip over each edge of the section.

In some plastics guttering systems, sections of guttering are cemented together in narrow union clips. To repair such a joint, you will need a new, matching section of gutter about 600mm long, some solvent cement and two new union clips.

Use a try square to mark cutting lines about 300mm from either side of the leaking joint, then cut along one of the lines with a hacksaw. Stick masking tape along the cut and cut along the second line so that the section containing the joint is severed.

Unclip the cut section from the gutter brackets, remove it and use it for sizing up the new piece.

Apply solvent cement to one side of both new union clips and fit a clip to each end. Now slide the outlet end of the existing gutter – which is always left unsealed to allow for expansion and contraction – along to give room to position the new section.

Apply a further layer of cement to the clip which mates with other end of the run and join the new section. Finally, cement the other clip and slide the outlet end of the gutter back to mate with it.

On systems which use combined union brackets, silt bridged joints are used. The silt bridge clips into the union to prevent debris working its way into the joint and causing leaks. Leaks in such joints will be due to cracks – either in the bridge or in the union bracket itself – and can be remedied by replacing the defective part with a matching new one.

To fit a new silt bridge, hook one end under the front of the union clip and snap the other end under the lip at the back of the gutter.

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