Crystal clear water starts with standard salt and a swimming pool salt chlorinator. Salt being introduced to around 4000 parts per million (4000 ppm). Most domestic standard systems work around this value. This being around the concentration of a human tear drop. At this level just about has a taste. This concentration is around 10% of seawater values. Some of the latest units on the swimming pool market can work down to very low levels of around 1500ppm or less but with the downside of lower chlorine production levels per hour.
A swimming pool salt chlorinator works by the process of electrolysis. The pool water with its salt load being pumped around the pool system in the normal cycle of filtration. Thus passing through the electrolytic cell. This splits apart the salt (sodium chloride) into sodium and chlorine gas. The chlorine gas is dissolved in the pool water similar to the bubbles in a fizzy drink, and circulates around the pool to sanitise the pool water. This result is the same as adding chemical chlorine to the water. The sodium and gas recombine back into salt over a few hours. During the normal process of the pool water being circulated, pumped and filtered the recombined salt gets split again and the whole process begins again without additional salt.
Super efficient as most chlorination systems do not require additional pumping power. They normally use the flow of water during the normal filtration times. Salt does not evaporate and the only loss is by the cleaning and backwash routine. Splashing and wet bodies exiting the pool. On the average domestic pool this minimal loss can be compensated for by adding further salt as required after testing in any top up. Loading of fresh water to give the 4000ppm is around 4kg of pure salt per 1m³ of water. With simple maths top-ups and the lower ppm levels required can be worked out.
Some additional plus points are reduced stingy eyes compared to chemical chlorine. Its a much nicer product on the skin with in general greater ph balance. Therefore has not the feeling of full blown sea water but does offer a pleasant skin affect. Some care must be given to salt chlorination as it can raise the ph level in the pool. Not a bad thing in low ph water areas. In water areas with higher then normal ph, if required it is a simple task to add a buffer solution.
The salt cell (Electrolysis Cell) in domestic use, are mainly manufactured from Titanium alloys. They work by applying a very low DC voltage to the plates of the cell. Around the power of a 12v car battery. The salt is then split as it passes between the cell plates one negative and one positive. If a build-up of scale is present on the cell plates the voltage on auto cleaning systems is simply reversed. The scale dissolving back into the pool water. This is an automatic process controlled by a timer within the cell control box.
We advise to use pure salt 99.99%, in fact food grade, with minimal caking agent, High concentration in the cheaper online product can damage equipment and reduce the lifespan of salt cells.