Blocks of flats have a number of pipes running through walls, under floors and through ceilings and 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.

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

1: Broken Or Perished Seals

These are 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: 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;

3: 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.

4: Incorrect Appliance Installations

These can things like a cold feed to hot supply, or ill-fitted power shower pumps etc, causing joints to fail.

5: Unsupported Pipes

They can lead to sagging then to blockages and unpleasant smells;

6: Pipes With Too Many Bends

The incorporation of too many bends along with an inadequate number of fixings can lead to noise and performance issues.

7: Poor And/Or Over-Notching To Joists:

Poor and/or over notching to joists can cause floors to become ‘springy’ and in extreme cases could potentially lead to floor failure and collapse.

8: Badly Supported Tanks and Pipes

These can be susceptible to leaks or splitting.

9: Leaking Toilet Overflow Pipe

A constant sound of running water from the toilet overflow pipe can cause damage to the exterior of the building because water is escaping onto the ground below. This will cause the wall to stain, damage mortars and quite possibly lead to water ingress elsewhere. Vegetative growth can also likely occur.

10: Vibrations Of Appliances

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 as should the washing machine hose as this is a major cause of leaks.

11: Plumbing Corrosion 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.

Other areas that can cause plumbing leaks are no insulation on cold-feed pipes, leaking hot/cold supply pipes, supply and waste pipes (including traps), hot water pumps or boilers, repairs to individual central heating systems and dripping taps (the latter of which can often be repaired by replacing a washer).


The risks presented by a water leak extend far beyond simple water damage, and every leak, no matter how small, requires a quick remedy to remove any potential danger. This is because water, (and the contaminants it contains) acts as an electricity conductor 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, result in sparks that start a blaze, sometimes with fatal costs.

Both these photographs show what happened on our block when a slow plumbing leak was undiagnosed coming from a tenanted flat into the empty flat beneath and the subsequent ceiling collapse! This empty flat was a complete nightmare to bring under control and more on this can be read here.




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