Plumbing problems

Copper pipework

Central heating leaks

Central heating distribution pipework running off a boiler will usually be under significant pressure, created by feeding mains supply into the network when topping up. A pressure gauge on the boiler will tell you if the central heating system is up to pressure or losing pressure from leaks. As a guide only, typical central heating circuit pressure may be from 1–2 bar (lower when cold).

Leaky copper compression fittings

A proliferation of compression fittings under a bath or sink usually looks ungainly and unprofessional, and each one is a potential leak. Professional plumbers are more likely to use soldered 'Yorkshire fittings', or the even more professional 'end-feed fittings'. Yorkshire fittings are pre-soldered, whereas the end-feed fitting is sold without integral solder.

Visual inspection of copper pipework can mislead you into thinking all is well. On one occasion the author stripped out some old central heating pipework and was amazed to find one section of pipework fell apart as it was removed from its brackets. One 15mm copper tube end had been fed into its straight connector by only 2–3mm – just enough to somehow remain intact until it was disturbed.

To avoid this, plumbers should place a pencil check mark on the tube to be fitted into a connector, so they can be sure the pipe end is fully home before firing up the joint. Soldered joints are, in the main, less likely to cause leaks than compression fittings. For a compression fitting, the end of the tube is fitted with an 'olive' (a metal ring), and a nut forces the ring against the mating surface of the straight connector, elbow bend or 'T' fitting. Professional plumbers tend to make the connections without using any jointing paste. However, jointing paste helps make a watertight and reliable joint, and when it hardens up actually helps bind the joint. But there have been cases when plumbing installations – for example, in hospitals – have failed at the snagging stage, as paste in compression joints was deemed a potential health hazard. Pipework needs to be carefully set out, or compression joints may fail. Pipes need to enter the fitting in line with the fitting, or a good joint may not be achievable. Pipework should not be under any tension or there could be a tendency for the joint to spring apart. If you need to physically pull the pipe towards and into the fitting you have a problem – the pipe was cut too short.

An end cap such as the one in the picture below was used to terminate pipework to a shower undergoing maintenance. The owner departed for a holiday. Disaster struck. A neighbour, intending to be a good neighbour, turned on the property mains stop valve so that the garden tap could be used to water the owner's back garden plants. As the neighbour watered the plants, she heard the sound of trickling water in the neighbour's house. Water was indeed cascading down the stairs and through the first floor ceiling. She realised there was a problem and turned the pavement stop valve off. The owner had turned off the house stop valve before going on holiday, realising that the shower cold water feeds had been left in a risky state with only end caps to hold back water. By turning on the mains stop valve in the pavement, the neighbour had caused the end cap to be forced off by the sudden change in pressure.

This is a 15mm compression end cap. It could be used where a cold or hot feed is temporarily out of use, or perhaps during plumbing work when connections to a bath, basin or sink are not yet completed.

Considerable experience is needed in tightening nuts – it is more likely you would under-tighten than over-tighten.

Fittings need to be locked on the pipe by a very tight olive, or you risk a flood. If you are at all unsure here, consider soldering on an end cap while the pipe is dry. And if you turn off the water main in the pavement, tell your neighbour to leave it well alone.

Water main connections using modern plastic tubes may fail if there is lack of attention to detail. You should not attempt to tighten up a compression fitting to a plastic pipe without first fitting an inner thimble.

Leaky push-fit connections

Plastic push-fit pipework is becoming more common for mains, low pressure hot and cold distribution pipework and central heating. This pipe system is not suitable for gas.

Figure 1: A new plastic pipe is to be connected to copper pipework. See at the end of the plastic pipe the metal rim of the stainless steel thimble, which must be fitted into the pipe’s end before the 15mm compression straight connector is fitted and tightened up

Those of us who have for years painstakingly bent, prepared and soldered copper plumbing are perhaps a little suspicious of new technology. We might associate plastic pipework with the lesser skilled in the industry, but this can be unfair. There are some clear advantages in this plumbing option, as set out below. Well-executed joints will not leak, and 1 manufacturer is sufficiently confident in their push-fit system to offer a 50-year guarantee on pipe and fittings.

Figure 2: A modern push-fit straight connection, suitable for mains, hot and cold water distribution. See above the fitting a special grab wedge for pulling off olives when re-using a fitting. Dedicated pipe cutters should be used and spray joint lubricant is sometimes needed. Tube and fittings courtesy Hepworth Building Products, www.hepworth.co.uk

The connections of the range the author tested are 'idiot proof'. Integral O-ring seals are even pre-lubricated, and there are guidemarks on the pipework to ensure that the end of the pipe is inserted sufficiently into the fitting. However, in spite of the exhaustive instructions from manufacturers, leaks could occur for any one of several reasons:

  • the fitting is not clean when used, e.g. when fittings collect site dirt, through careless storage or handling;
  • the O-ring is displaced due to insertion of a very roughly cut pipe end;
  • the pipe has not been properly inserted into the fitting;
  • chemical breakdown of plastic fittings, due to use of oil-based plumber's sealing pastes;
  • pipework affected by heat/fire: temperatures over 125°C cause damage;
  • pipework damaged by rodents/vermin;
  • pipework damaged by UV light;
  • fittings used on unsuitably sized pipework, e.g. non-metric copper (i.e. imperial);
  • fittings used to connect unsuitable pipe material, e.g. stainless steel or chrome shower pipework: the fitting can be pushed apart as the internal plastic gripper will not function correctly; or
  • pipework or fittings drilled, cut or otherwise damaged accidentally or by vandalism in use.

Failures of construction components will nearly always occur from poor installation and misuse of the product. You really do need to read the product guidelines.

Lead-to-copper connections

Leaks at joining of lead to copper used to be much more common.

Figure 3: A 'taft' joint by the author – of lead to copper. The lead piping has been flared using a thimble. The joint is then infilled with plumber's solder and 'wiped' using a moleskin. But this is fairly time-consuming, and if not perfectly executed, could leak. Pipes need to be dry to solder. To the right, as viewed from above, the modern answer. No need for a wiped joint! A compression coupling connects lead to copper – a fairly quick and simple way of executing the connection. Above the joining of pipes, a stop valve and drain down valve