The following information has been originally sourced from the Ringley Group.

The pressure of the water that reaches property reduces depending on the number of stories above ground the incoming water mains has to rise. Water pressure will also be reduced by each spur off the mains entry pipe into a property. Typically an incoming water mains pipe will be 25mm blue plastic pipe although some older blocks of flats may still have lead or iron pipework. Ideally this should be replaced as lead pipework can cause health and safety risks and iron pipework is prone to rusting.

Where the Water Mains Come into a Building

The typical points of entry for a water main are underneath a floor slab. Water mains pipes may directly feed appliances or feed directly into a water storage tanks/cistern  installed at attic or roof level. Our block has the latter. Where water storage tanks/cisterns are installed at high level then appliances are gravity fed from the stored water as opposed to mains fed from the incoming water mains. This may be advantageous in areas where water pressure is particularly low or where a dwelling is at high level as water pressure will significantly reduce at around the third or fourth floor level of a building.

Causes of Leaks

A leak from a water mains pipe is usually caused by a defective in-let pipe, usually before it reaches an appliance. This is because most appliances, i.e. baths, hand basins, kitchen sinks, boilers, toilet cisterns, cold water storage tanks and immersion tanks are fitted with overflows, fail safe devices which direct a water leak outside the building.

Who is Responsible for Repairs?

Generally leaks before the first stopcock into the building are the water supplier’s responsibility.

Leaks after the first stopcock into the building (but before the water mains reaches any particular flat) are the responsibility of the freeholder/management company. Whilst buildings insurance policies usually cover the cost of tracing a leak and damage caused by the leak, it however unusual for them to cover the replacement of a defective pipe.

Where are the Stopcocks Found?

Stopcocks are usually located in the following areas:

  1. A riser cupboard just outside the flat;
  2. Under the kitchen sink,
  3. In a service cupboard on the ground floor of the common parts
  4. In a service hatch outside the communal entrance (external mains may either be hand operated taps or need a special water board tap key to turn on and off).


Mains pressure water leaks are arguably the most serious type of water leak as the pressure of the water will maximise the presence of defects within the pipe itself, such as weak joints for example. The first point of action is turn off the stopcock. When this is done some points to assist diagnosis are:

  1. Mains water leaks usually start suddenly, not over a period of time;
  2. Mains water leaks can only get worse;
  3. Mains water leaks will rapidly fill a bucket;
  4. Mains water leaks can only be clean water so if its not clean then its not the water mains!;
  5. Mains water leaks will not stop, unlike a leaking appliance:;
  6. Mains water leaks will draw water even if every appliance is turned off/shut down so running water will be heard near the inlet.

If a mains water leak cannot be resolved then the Fire Brigade should be called as they will be able to isolate the water supply, and shut down the electrics to affected areas for obvious safety reasons. If they believe the problem is the responsibility of the water authority they will have access to emergency contact numbers to assist.

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