The Basic Domestic Water System

Be sure you understand the layout and operation of your household hot and cold water services and drainage system before attempting alterations or improvements to bathroom or kitchen plumbing.

Cold water services

Your responsibility for the water supply to your home begins at the water authority’s stop-cock. This will be found at the bottom of a guard-pipe with a hinged metal cover, probably near to the front boundary of your property. From this point the service pipe travels underground to the house, usually rising into the home through the kitchen floor — often under the sink. Once above ground, this service pipe is usually referred to as the rising main

Another stop-cock should be fitted into the rising main a few inches above the kitchen floor. Closing this stop-cock is the first step that must be taken if a pipe bursts, a cistern overflows or in virtually any plumbing emergency. It will usually be necessary to turn it off before carrying out plumbing improvements. Make sure that you know where it is and how to turn it off.

In some, usually older, houses every tap and the lavatory flushing cistern are supplied with water direct from the rising main. In most modern houses, though, only the cold tap over the kitchen sink — and perhaps a branch to an outside tap or a washing machine — is connected directly to the rising main Other taps and the lavatory flushing cistern are supplied with water from a main cold water storage cistern, usually situated in the roof space. Water flows into this cistern from the rising main via a ball valve or float valve.

Hot water services

The main cold water storage cistern, which should have a capacity of 227 litres (50gal) also supplies the hot water storage cylinder with water under constant low pressure. Water in this cylinder may be heated solely by means of an electric immersion heater, solely by means of a boiler or — quite often — by means of a boiler during the winter and an immersion heater during the summer.

Note that a vent pipe rises from the dome of the cylinder and terminates open-ended over the cold water storage cistern. The distribution pipe taking hot water to the kitchen and bathroom is taken as a branch from this vent pipe above the level of the hot water cylinder. So the cylinder cannot be drained from the hot taps.

In normal use this is an important safety factor. To enable the cylinder to be drained when required, a drain-cock is provided near the boiler or, if the cylinder is heated by an immersion heater only, at the base of the cold pipe supplying the cylinder.

Never attempt to drain the cylinder from either of these drain-cocks without switching off the electric immersion heater and letting out the boiler fire.

This kind of system, in which water is heated solely by an immersion heater or in which water in the cylinder circulates directly through a boiler, is called a direct hot water system.

If your home has a central heating system heated by the same boiler that is used for hot water supply, you will have an indirect system. Even if you haven’t a central heating system at present, an indirect system may have been installed if you live in a hard water area or if it was thought that central heating might be provided at some time in the future.

With an indirect hot water system, the water stored in the cylinder does not circulate through the boiler. It is heated indirectly by a closed coil or heat exchanger through which water heated in the boiler passes.

This closed coil or heat exchanger and the circulating pipes that connect it to the boiler are called the primary circuit. It is to the primary circuit that any central heating system must be connected.

The primary circuit of a conventional indirect hot water system is supplied with water from a small feed and expansion tank, usually sited near to the main cold water storage cistern in the roof space. A vent pipe from the primary circuit also terminates open-ended over this tank.

There are, it must be added, patent self-priming indirect cylinders that do not need a separate feed and expansion tank. They have a specially designed inner cylinder which serves as a heat exchanger. When the system is first filled with water from the main cold water storage cistern, water flows through this inner cylinder into the primary circuit. It is prevented from returning to the outer part of the cylinder by a giant air bubble or air lock that forms in the inner cylinder. A conventional indirect system gives a more positive separation of water in

the primary circuit and the domestic hot water. It therefore affords a more certain protection from internal corrosion.

Some householders, investigating their hot and cold water systems, will find that they have a packaged plumbing system or a two-in-one unit. These are often used where a large house is converted into two or more flats or where an older home is modernised.

A packaged plumbing system is, quite simply, a cylinder hot water system in which the cold water storage cistern and the hot water cylinder are brought into close proximity to form one compact unit. Packaged plumbing systems may have direct, indirect or self-priming indirect cylinders.

Above-ground drainage

Houses where the plumbing was installed prior to the 1960s are likely to have a two-pipe above-ground drainage system. In such a system a rigid distinction is made between soil fittings such as lavatories and waste fittings such as baths, basins, bidets and sinks. The outlet pipes of soil fittings are connected direct to the main soil and vent pipe but the outlets of waste fittings discharge over a yard gully and are not allowed to connect directly to the drain.

Where upper floor wastes are concerned this usually meant that the branch waste pipes discharged over a rainwater hopper-head and were then conveyed down to a yard gully through a length of rainwater down pipe.

In a single-stack drainage system all wastes discharge into one main soil and waste stack often made of UPVC or other plastic and usually contained within the fabric of the building.

The success of a single-stack drainage system depends upon very careful plumbing design. The Building Regulations require that you should always notify the district or borough council’s building control officers before making any addition to a drainage system. This is particularly important — not only to comply with the law but also to safeguard your family’s health — where an addition is to be made to a single-stack drainage system.

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