The use of heavy metals for purifying water by has been practised for many hundreds of years. The Ancient Greeks found that water kept in silver containers mysteriously purified, and that algae didn’t grow in copper water pots. Extensive research into this action of metals in water was not undertaken until the late 19th Century. This research resulted in the development of the “Katadyne” water treatment process. This required that water be passed through various porous materials impregnated with silver. Some of the metal would become ionised and pass into the water as positive ions. The water was purified as a result.


Over time, the Katadyne porous filters became less effective and were difficult to clean. This resulted in the introduction of the Electro-Katadyne process.  Here an electric current was passed between silver coated sand beds which gave a level of control over the ionising process.



As has been described, silver acts as a disinfectant when dissolved in water as ions. Similarly, copper ions, prevent algae growth. These metal ions are generated in the pool water through the electrolytic dissolving of silver/copper alloy electrodes. An ioniser is an ion-generating devise which is installed in the circulation system. The devise consists of two units. The electrode assembly(a copper electrode & a silver electrode), and the electronic control unit. The control unit supplies an electric current to the electrodes which, through the process of electrolysis, pass either silver or copper ions into the water.



The silver and copper residual levels can be measured using a specifically designed test kit.  However most manufacturers recommend maintaining a chlorine disinfectant residual as well.  Although metal ions kill algae and bacteria and provide a measurable residual, they do not oxidise organic waste.  It is therefore necessary to shock treat or super chlorinate the pool, to oxidise any build up of organic waste and maintain disinfecting action.


Be aware that dissolved metals can stain a pool/spa or discolour the water. Be careful to keep the copper/silver residual levels within the manufacturers’ recommendations.


Electrolysis of metals is a means of purifying pool/spa water, not chemically balancing it. Therefore normal procedures should be adopted to correctly balance the water – see WATER BALANCE.