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BUILDING BRIEFING:

Testing the water

In the first of a series about water supply and drainage, Peter Ryland, a surveyor specialising in residential buildings, examines cold water systems and problems that can arise.   The property manager must be aware that a minor problem with a water pipe or storage tank can cause hundreds, or even thousands, of pounds worth of damage to a building.  In properties where water supply systems are in modern materials the problems for the property manager are greatly reduced. However, many properties still have old materials e.g. lead pipes, cast iron tanks, and to make things worse old buildings may have had alterations and additions in modern materials.

Mains water supply

The incoming water supply main is usually in front of the property with a stopcock where it enters the boundary, and these days often has a water meter by the stopcock. It is the responsibility of the consumer to maintain the pipework from this point on.

The modern water supply pipework is usually of plastic and should be put at least 750mm below ground level to prevent freezing in cold weather. In older properties up to the 1950s the normal material for supply pipes was lead, which can cause pollution of the water supply, especially in soft water areas, and was prone to leaks and burst pipes. Compared to modern materials it was also difficult to repair.

Where the supply pipe enters the building, often in the kitchen, a stop tap should be provided. This should be easily accessible so that the water can be quickly turned off in an emergency. The property manager should advise the tenants of the location of the stop tap so that they can turn off the supply when necessary.

Once inside the building the cold water system can be either a) Direct or b) Indirect.

Direct cold water system (Fig1)

With this system all fittings are fed directly from the main and there is no need for a storage tank. The water enters the property through the rising main at high pressure and therefore all fittings must be suitable for high-pressure e.g. wc cistern ball valves.

One of the problems with direct systems is water hammer when the supply pipes vibrate. It can be caused by pipes not being properly secured, or worn fittings, such as ball valves.

Direct cold water systems are only suitable where there is a reliable and continuous supply of water at a constant pressure. With this system, if there is an interruption to the supply (mains repair or fracture), then of course there is no water available in the property for any purpose. With the direct system hot water is usually supplied by a multipoint.

From a management point of view the advantage of a direct system is that there is no storage tank in the roof, which could overflow or fracture causing considerable damage.

Indirect cold water system (Fig2)

With this system the mains supply is taken via the rising main to a storage tank, usually situated in the roof space, and fittings are fed from this at low pressure and so low-pressure fittings are required in cisterns etc.

Water for drinking purposes should not be taken from a storage tank and therefore drinking water should be made available from the mains, usually by supplying the kitchen tap directly from the mains.

This type of system is required when the supply is not reliable, usually due to large variations in pressure. This occurs in very densely populated areas or, the exact opposite, in a remote location where the property is at the end of a main.

Storage tanks (Fig.3) used to be of galvanized iron, which tended to rust and eventually fail. These days tanks are usually of plastic or fibreglass. Modern tanks are not so rigid and usually need a framework and to be supported on load-bearing boarding. In many older properties, where the tank has been replaced, the original will be left in the roof space because it does not fit through the access hatch.

Ball valve floats were originally of copper, which tended to perforate and allowed the float to fill with water and sink, thus preventing the valve from stopping the water entering the tank. Floats are now made of plastic.

An overflow pipe should be provided which is properly fixed to prevent sagging, and should discharge into a prominent position outside so that it will be seen quickly. The pipe should be large enough to take away all the water if the valve fails, otherwise damage will be caused by an overflowing tank.

cold_water_system                             Fig 1                                                                                  Fig 2

Problems

Older buildings often had lead or galvanized iron pipes replaced with copper. The copper pipes were usually 1/2" or 3/4" diameter. When metric pipes and fittings were used instead of imperial fittings the size used were 15mm and 22mm. Initially there was no problem as fittings to connect imperial to metric were available, but these fittings are becoming difficult to obtain.

Water supply pipes are very useful for earth bonding for the electrical supply but care should be taken to ensure that earth bonding is not interrupted when plastic pipes or fittings replace copper. It is good practice to recheck the earth bonding after any plumbing work is carried out.

Cold weather precautions

As stated above cold water storage tanks are usually sited in the roof space and therefore should be adequately lagged. However, the space under the tank should be left clear to allow heat to rise from the building. Supply and distribution pipework within the roof space should also be lagged.
If the property is to be left vacant for any length of time the mains should be turned off and, equally as important, the system should be drained down.

In flats damage can be caused by water leaks from above, and the prudent property manager will have contact details of owners or occupiers of flats above the managed property. It is not only problems with hot or cold water supplies; washing machines leaking can cause a lot of damage!

Water meters

All new properties have water meters and many older properties have had meters installed in an effort to reduce ever-increasing water charges. It is therefore important that leaks are repaired quickly and valves and washers are kept in good condition.

Water leaks are usually evident very quickly but if there was a leak on the underground pipe between the boundary and the building it may not be immediately obvious. It is therefore prudent to check the meter frequently.

The basics

You can minimise potential problems by understanding your system, and performing regular maintenance checks:

  • Ensure the tenant knows where the stopcock is and when to use it.
  • Have contact details for adjacent flats in case of leakage.
  • Make sure a tank in the roof is in good condition and appropriately lagged.
  • Turn off supply and drain pipes if the property is unoccupied –"Empty Property – Empty Pipes"
  • Check the condition and operation of valves, tap washers, washing machine connections.
  • Check water meter readings – these may give an indication if a leak occurs out of sight.