Plumbing An Electric Shower

If you would like to install a shower but think you can’t because there’s insufficient water pressure, you might like to consider an instantaneous electric shower. It’s connected directly to the mains cold water supply, so you are guaranteed a good jet of water. And as you heat only the water you use, it’s very economical to run.

Until quite recently a properly functioning shower was all but an impossibility in many homes. Either it lacked the cylinder storage hot water system needed to supply a conventional shower, or the system that existed wouldn’t permit a successful shower installation. For example, the main cold water storage cistern might have had insufficient capacity to supply the cold side of the shower mixer as well as feeding the hot water storage cylinder, or it may have been situated at too low a level to give adequate pressure at the shower rose.

The increasing popularity of showers has led to two new developments: the electric shower pump which increases pressure at the shower rose where this is inadequate; and the instantaneous electric shower.

Going back to geysers

There is nothing particularly new about appliances which heat water instantaneously’ as it flows through them. The Edwardian geyser, installed over the bath in many a turn-of-the century middle-class home, was an early example. The modern single-point or multi point instantaneous gas water heater – which can provide hot water for the whole house is its direct descendant. Instantaneous water heaters were designed for connection directly to the rising main so they could operate under mains pressure. They needed no cold water storage cistern or storage cylinder arid they had the advantage that heat energy was expended only to heat water that was actually to be used at that time.

However, until a couple of decades ago, the only instantaneous water heating appliances that were available were — like the early geysers – gas-operated. It just wasn’t possible to devise an electric appliance that could ‘instantaneously’ heat a sufficiently large volume of water to fill a sit-down bath, a sink or even a wash basin, It still isn’t. But manufacturers have now produced electric water heaters powerful enough to provide a steady flow of hot water for spray hand-washing over a washbasin in a WC compartment and for the provision of a shower. In neither case is very hot water needed in large volumes.

An instantaneous electric water heater is a relatively compact appliance that needs only to be connected — by means of a 15mm (½in) branch water supply pipe to the main supply, and to a suitable supply of electricity. It is normally operated by a flow-switch which ensures that electricity is switched on only when water is flowing through the appliance. As it does so, it passes over powerful electrical heating elements.

Temperature control was originally obtained solely by controlling the volume of water flowing through the heater. Opening up the tap or control valve produced a heavy flow of cool water As the control valve was closed down and the flow diminished, warmer and warmer water was obtained from the shower spray.

The crude, early models were something of a disaster and were frowned on by water authorities and electricity boards. They rarely provided a satisfactory shower. The flow was markedly less than that from a conventional, cylinder-supplied shower.

Flushing the WC or opening up any other tap in the house would reduce the pressure of the water entering the heater, so reducing the flow and raising the water temperature from the shower spray. Such unpredictable temperature changes could cause serious scalding to an unsuspecting user. Other problems arose from the hard water scale that tended to form on the heating elements.