Blocks of flats will have a number of pipes running through walls, under floors and through ceilings. Leaks are usually obvious, such as large amounts of water coming through ceilings, appearing under the floor, or wet patches showing on the wall or floor even when the weather is really dry. A service duct (or main stack) within the property should be fully accessible because it provides access to valves, all main services, and rodding eyes.

Some flats will share such services with the neighbouring flat.

There are a number of potential causes of plumbing leaks, with the following information sourced from the ARMA downloadable fact sheet ‘Water Leaks’

  1. Defective seals: found around baths and showers and which are white flexible beads which run around  the bath/shower and allow water to run back to the baths/showers. When the mastic seal is damaged, split, loose or curling away from the wall or bath, water can freely run down the back of the bath/shower, and eventually make its way through the ceiling and into the property below, often through a light fitting;
  2. Gaps in grouting: these can allow water in behind tiling causing damp patches, tiling to come loose and again, the risk of water leaking into the property below;
  3. Unconnected waste pipes;
  4. Incorrect installation of appliances: these can be a cold feed to hot supply, or ill-fitted power shower pumps etc, causing joints to fail;
  5. Unsupported pipes: this leads to sagging then to blockages and unpleasant smells;
  6. Incorporation of too many bends; this, along with an inadequate number of fixings can lead to noise and performance issues;
  7. Poor and/or over-notching to joists: these can cause floors to become ‘springy’ and in extreme cases could potentially lead to floor failure and collapse;
  8. No insulation on cold feed pipes
  9. Badly supported tanks and pipes: these can be susceptible to leaks or splitting;
  10. Irregular noise from a toilet: This can be theflush cycle taking longer than it normally does and is often remedied by adjusting the valve or replacing the inlet valve washer. A constant running sound on the other hand can cause damage to the exterior of the building because the external overflow is allowing water to escape onto the walkways below. In icy conditions this could cause a hazard. Staining will occurr on walls, damage mortars and lead to possible water ingress somewhere else, as well as encourage vegetative growth;
  11. Degraded seals: When found around the kitchen worktop and around the sink, the gaps they create can often cause water to penetrate down the back or into other properties;
  12. Frequent vibrations: these can cause the outlet connections of dishwashers and washing machines (found under the kitchen sink) can come loose due to frequent vibrations  so these connections should be regularly checked. Frequent checks should also be carried out on the washing machine hose as this is a major cause of leaks.
  13. Leaking hot/cold supply pipes, supply and waste pipes including traps, hot water pump or boiler;
  14. Repairs to central heating systems (unless the system is for a communal area of the development);
  15. Dripping taps: These can often repaired by replacing a washer;
  16. Corrosion of the plumbing or joints not fully water-tight: Corrosion can be internal as result of more than one type of metal being used in the plumbing, or external  which is often as a result of concrete or cement coming into contact with copper pipes. It can also be caused by flexible tumble dryer vents extracting into a room rather than outside of it. It typically manifests itself as a small isolated damp patch, without any brown staining, that gradually grows, ‘bubbly’ plaster at the edge of the patches with water appearing if the leak is near (or above) the surface.


The risks presented by a water leak extend far beyond simple water damage, and every leak, no matter how small, requires swift attention to eliminate any potential danger. This is because water (and the contaminants within it) acts as a conductor of electricity, which means it can carry an electrical current to whatever it touches, including people. It can also cause a fire risk because even if a leak is small, water may find its way into light fixtures and other electrical wiring. In most cases this will cause a harmless short but touching a switch when water is pooling in a light fixture for example can result in an electric shock but even worse, it can sometimes result in sparks that start a blaze, sometimes with fatal costs.


In theory leaks and burst pipes are easier to correct than penetrating damp but if there are no obvious signs of a leaking pipe, then cutting off the incoming water at the stopcock and draining the hot water system (by turning all the taps on) will quickly empty the pipework and dripping water should stop. Leaks which are more difficult to trace are ones in storage tanks, cylinders and waste pipes, but small steady leaks that are difficult to find (or not even known about) can be slowly causing extensive damage.

Our block had a major situation with an undetected leak which occurred not long after we took over. The ceiling of a flat at the rear of the property had partially collapsed in the kitchen below due to a slow, steady leak underneath the floor of the flat above. It may have caused less damage if the owners of the empty flat beneath kept a check on it but they didn’t. In fact it remained empty for years and even when we took over management it took at least a couple more years to get them to fix it but that’s another story


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