Salt chlorinators

An alternative means of sanitising your pool

Salt chlorinators, or chlorine generators, use the process of electrolysis to create sodium hypochlorite, or liquid chlorine. Saltwater passes through an electrolytic cell which converts salt in the water into chlorine gas which, when dissolved in water, becomes liquid chlorine. They consist of two main parts, the cell and the power pack.

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The cell

The cell is where the chlorine is generated. It usually consists of a clear plastic housing containing electrodes. Anodes and cathodes are 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 principles of their operation remain the same. Caustic Soda is also generated in the cell, so a salt chlorinated pool will use more acid than other types of chlorination.

Some models that use a single polarity cell will need cleaning with 'Cell Cleaner' monthly. Cells that have reverse polarity are capable of self-cleaning and only need to be manually cleaned when white calcium deposits form in the cell.  

The average life of a cell is 2 to 3 years and chlorine output from the cell decreases with time. The first sign of deterioration is Black Spot Algae forming in the pool.

Power pack

A power pack is a box connected to the mains power which lowers the voltage to the cell for it to work. It also has a dial to raise or lower the chlorine output of the cell and a timeclock to operate the pump. 

The power pack will not operate if no water is flowing through the cell and will shut down if too much salt is in the water or if salt is added with the pool cleaner, still attached (which will suck up neat salt). The salt cell will also be damaged if the salt content is too low. Salt can only be lost through backwashing, water being splashed out or the pool overflowing. Consult the manufacturers’ instructions for ideal salt levels and correct operation.

Selecting a suitable salt chlorinator

A number of factors will affect the selection of a salt chlorinator.

  1. the size of the pool or spa - larger pools need larger chlorinators
  2. bather load - heavy loads consume more chlorine
  3. size of the filtration system - poor water flow will require longer running time
  4. summer water temperature – high temperatures and strong sunlight cause faster loss of available chlorine

How much salt to use

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 from 0.3% to 0.6% (3,000 ppm to 6,000 ppm) to effectively chlorinate a pool. These levels are about one seventh the level of salt in sea water.

The manufacturer's recommendations should be strictly followed to avoid damage to the chlorinator and to ensure adequate chlorine production.

Replacement salt is only required to replace normal consumption and loss from filter backwashing, splash-outs and any overflow due to rainfall.

Other chemical requirements

The requirements for chemical balance are the same for electrolytic chlorination as they are for traditionally chlorinated pools. pH, Total Alkalinity, 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 manually supplement with liquid chlorine to maintain correct chlorine levels, and regular super chlorination or shock dosing should be carried out.

An important consideration

When using salt chlorinators with gas or electric heaters and heat pumps, care should be taken to ensure the production of chlorine is adjusted to suit the pool or spa as the heaters internal components can be damaged by excessive salt and/or chlorine levels. This is particularly important when operating for extended periods during heat-up.

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