Problems with Sink Traps
RE-ASSEMBLING THE TRAP
Take care not to damage the rubber seals or over-tighten the nuts when reassembling a plastic trap. Silicone lubricant — as used to make push-fit joints on supply pipes — helps prevent damage to the seals.
If you find the trap leaks after refilling, don’t tighten the nuts any further. Instead, dismantle the trap once more and check for the following faults:
♦ Grit in the seal.
♦ Old jointing compound — this attacks the plastic.
♦ Serious misalignment between the various pipes.
♦ Distortion of the waste pipe end.
♦ Pinched, cracked or broken seals.
On some traps, the waste pipe simply pushes into the end of the trap. If possible, smear the ring seal with silicone lubricant to avoid damage during reassembly.
‘Universal’-fit connections are now taking over from push-fit joints. Fit the rubber seal on the outside of the waste pipe, before inserting in the trap.
Save the seals?
“Discard a seal which is obviously damaged. If a replacement is unavailable, improvise one from a good number of turns of PTFE tape; wrap this around the shoulder of the fitting, not around the thread. If the plastic nuts prove difficult toon, squirt a drop of washing up liquid on the threads.”
Siphoning out water
Where you’re faced by a bathful of water to empty before using caustic soda or dismantling the trap, you’ll find siphoning a lot quicker than baling with a bucket.
♦ Connect a garden hose to a nearby tap and turn it on for a few seconds to fill the hose with water.
♦ Keeping the hose filled, remove the tap end and plug it. Insert the other end in the bath and weight down near the waste outlet.
♦ Run the hose out of the window (or better, to a drain) below the level of the bath. Unplug the end and the water will siphon away.
Replacing a sink trap
A trap which is damaged or old and difficult to unblock, is best replaced with a modern ‘multifit’ design. There are many different patterns, but the ‘Universal’ type can be adjusted to fit virtually any pipe/waste outlet position. Remember to buy the 32mm (1-1/2″) size for a basin waste, a 38mm (1-1/2″) trap for other fittings.
Check before you start that the new trap will fit. If there is a gap to be made up between the trap and the existing waste pipe, buy a multifit push-fit connector and a length of the same-size plastic waste pipe.
♦ Sever the waste pipe as near to the old trap as possible using a.
♦ Unscrew the old trap with a large adjustable wrench.
♦ Fit the new trap on the waste pipe and screw to the outlet.
Persistent blockages in clogged sinks
If you have a complicated waste pipe run which is prone to regular blocking, it could be worth fitting an access tee to make clearing or auguring easier. As many waste pipes, particularly lead, are incompatible with certain fittings, it’s safest to use a push-fit ‘multifit’ tee fitting such as the McAlpine ‘VM’. The access branch can be sealed with a blank cap from the same range.
2. Sand the cut pipe ends smooth, then slip on the nuts and sealing rings and jiggle on the tee. Hand-tighten the nuts, and fit the blanking cap on the access branch.