Scale formation is all too common in hard water areas and its effect on the plumbing system can be quite startling. Protective measures are therefore all important. » Hill

You can tell whether you have hard or soft water by the effect it has on soap. Soft water dissolves soap readily, producing a rich lather; hard water tends to produce a sticky, insoluble curd that matts woollens, produces poor lather from shampoo and leaves a dirty tide mark round baths and wash basins. Another obvious sign is the amount of scale in a kettle; if the kettle regularly ‘furs up’, there is a need to protect your plumbing system from the action of hard water scale.

Hardness is caused by dissolved bicarbonates, sulphates and chlorides of calcium and magnesium. which are present in the geological structure of much of Britain in the form of chalk and limestone. The natural water table dissolves these mineral salts in varying proportions, so the hardness varies from area to area depending on the source of supply. Water hardness can be expressed in various ways. The most common measurement is parts per million of carbonate hardness in water; for example water of 200ppm contains 200g of carbonate hardness per cubic metre of water. It is generally accepted that water containing between 100 and 200 ppm is ‘medium hard’ and above that it is ‘hard’ to ‘very hard’.

Excluding the South West and a few small districts, the whole area south of a line drawn from the Wash to the Bristol Channel has hard water. Above this line, the East Midland counties and the North East are predominantly hard water areas.

HOW HARD WATER affects PLUMBING When water is heated to temperatures in the region of 71°C, the dissolved bicarbonates of calcium and magnesium are changed into insoluble carbonates which are deposited as scale on immersion heaters and the internal surfaces of boilers, hot water cylinders and pipework.

Because scale is a poor conductor of heat, it insulates the water in the boiler from the heat source and, as scale accumulates, more fuel is needed to heat the same volume of water, pipes become blocked and circulation is impeded. Each time the water is heated more scale builds up, insulating the metal of the heater from the cooling effect of the water and leading to burnt out immersion heaters and leaking boilers.

There are two ways of dealing with the problem. You can reduce or prevent the formation of scale by various means, without softening the water, or you can use a water softener.


You can reduce the formation of scale by various mechanical means or by using a chemical scale inhibitor. Since scale forms at temperatures around 7 PC, you can help prevent it by keeping the thermostat of your electric immersion heater set at 60°C. If you have a gas or oil-fired boiler, you should be able to keep the temperature of thatat60°C too, but a solid fuel appliance may be less controllable. If you have a direct hot water system, you can convert it to an indirect system, which is less susceptible to scale on radiator circuits.

CHEMICAL SCALE INHIBITOR Scale formation can be reduced or prevented in many cases, by introducing into the water supply minute quantities of a proprietary non-toxic chemical. It stabilizes the bicarbonates in the water supply to prevent an insoluble scale when heated. But it does not soften the water and the elTcct on soap will be unchanged.

The chemical crystals come in an open-work plastic container which you suspend in the water of the cold water storage cistern. They dissolve very slowly in the water and are effective for six months, when the container should be refilled. There is a special grade of crystals for a combination tank since the water in the cold water feed tank becomes warm because of its proximity to the hot water storage cylinder.

Some scale inhibitors have a dual role. In naturally soft water areas the crystals can protect the system against corrosion caused by the acidic nature of the water. Other crystals can be used to protect hot water supply appliances fed directly from the rising main. In this case a special dispenser is plumbed into the supply pipe leading to the appliance. Fit it on the outlet side of the stopcock in the cold water pipe but as far away as possible from the hot water storage vessel. It can be fitted TO A horizontal or vertical pipe. In both cases you need to leave clearance to allow for refilling with new crystals. If you fit A stopcock each side of the container, you will not need to turn off the water at the mains when you renew the crystals. Use the same type of metal for the connections between the stopcocks, scale reducer and storage vessel.

MAGNETIC WATER CONDITIONER This conditioner, recently developed for domestic use, precipitates the hardness salts in the water into microscopic crystals by passing the incoming mains water supply through a magnetic field.

The self-powered permanent magnet prevents the normal conglomerates of interlinked crystals forming insoluble scale as long as the water is in motion. The magnetic unit does not affect water pressure and, as long as the individual hardness salts are held in suspension by water flowing, existing scale will dissolve.

The small compact magnetic unit is easily plumbed into the rising main as it enters the house. It can be mounted vertically or horizontally as long as it is easily accessible. Since there is an integral strainer which requires occasional cleaning, it is advisable to fit a stopcock on each side of the unit.

If continuous water flow is required while any servicing work is being carried out, a bypass with its own stopcock may be introduced round the UNIT.


The installation of an automatic water softener will convert even the hardest water supply to total softness and give complete protection to the hot water and central heating systems.

A mains water softener operates on the principle of ‘base exchange’ or, as it is commonly called, ‘ion exchange’. A container, plumbed into the rising main, holds a specially manufactured synthetic resin through which incoming hard water flows. The resin is not a chemical and no chemicals are used in the softening process. The resin absorbs the unwanted calcium and magnesium ions and releases sodium ions in their place.

After a period of use, the resin becomes saturated. When this happens the softener automatically washes, rinses and flushes the hardness salts from the resin with a salt solution, leaving the resin ‘regenerated’ so the softening process may continue. All you have to do is put fresh supplies of common salt in granular form into the appliance at infrequent intervals to keep the salt topped up to the recommended level.

When buying a mains water softener, make sure you get the size suited to the needs of your household; the supplier will be able to advise you on this. It is possible to install a water softener yourself, but since installation may vary slightly from one model to another it is important to follow the manufacturer’s instructions.

The total removal of the hardness salts from water means soap no longer produces sticky insoluble curds. This gives rise to other benefits not possible with the alternative methods of scale prevention. Not only will softened water slowly dissolve existing scale deposits, but it will also make savings on soaps, shampoos and similar items as well as prevent washing machines clogging and dishwashers breaking down.

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