The electrolysis process is achieved by passing the salt water solution through an electrolytic cell which converts sodium chloride (salt) in the water into chlorine gas which when dissolved in water, becomes sodium hypochlorite (liquid chlorine). So you are in fact producing your own chlorine to sanitise the pool.
The cell usually consists of a clear plastic housing containing the electrodes, made up of an anode and a cathode made from or coated with exotic metals like platinum, titanium and aridium. The cell and electrodes may differ in size and configuration depending on the brand of chlorinator, however the principals of their operation remain the same.
Most chlorinators these days are equipped with controls to regulate the amount of chlorine produced, depending on individual requirements, and are fitted with a gauge to show the set level.
Some units come with time clocks and in-built facilities for pool lights and other more sophisticated options. Remember choose the one that best suits your requirements and budget but also consider your lifestyle and how you intend to use the pool.
SELECTING A SUITABLE UNIT
A number of factors should effect the selection of a salt chlorinator.
Size of the pool or spa – larger pools need larger chlorinators.
Bathing load – heavy loads consume more chlorine.
Size of the filtration system – poor water flow will require longer running time.
Summer water temperature – high temperature and strong sunlight cause faster loss of available chlorine.
HOW MUCH SALT?
The amount of salt needed for the salt chlorinator to produce sufficient chlorine varies, depending on the type of chlorinator. Most models require only weak salt solutions of between 0.4% to 0.7% (4000 ppm to 7000 ppm) to effectively chlorinate a pool. These levels are between one fifth to one tenth the level of salt in sea water. The manufacturer’s recommendations should be strictly followed to avoid damage to the chlorinator and to insure adequate chlorine production. Replacement salt is only required to replace normal consumption and loss from filter backwashing, splashout and any overflow due to rainfall.
Although there are some maintenance free cells available, most brands of cells will require cleaning periodically, to remove calcium deposits which build up on the electrodes as a result of the electrolysis process. This cleaning is usually accomplished by soaking the electrodes in a weak acid solution. NB. The manufacturers instructions should be strictly adhered to regarding cleaning, to avoid damage to the assembly.
OTHER CHEMICAL REQUIREMENTS
The requirements for chemical balance are the same for electrolytic chlorination, as for traditionally chlorinated pools. Total Alkalinity, pH, Calcium Hardness and chlorine levels should be checked regularly. Chlorine stabiliser (isocyanuric acid) should be added to the pool and maintained at approx 30-50ppm, to reduce chlorine loss due to UV rays.
During periods of high bather load, it may be necessary to superchlorinate to maintain correct chlorine levels and regular superchlorination or shock dosing should be carried out.
For more information on pool maintenance see WATER BALANCE.