Salt Water Chlorinators
In the last issue we covered chlorine, the different kinds and dosing. In this issue I would like to explain why the salt chlorination in my opinion is the best way to have a relatively easy swimming pool to manage and enjoy here in Thailand First thing is to understand that when we talk about a salt water pool, it doesn’t mean sea water salt concentration.
We use about 15 % of sea water concentration. Unless you taste it you would not know it had salt in the water. The reason for the salt is that a chlorine generator is installed in the pump room and this uses salt to create chlorine. Yes it is still a chlorine pool. However the level of chlorine needed is in most cases a lot less. Especially when the natives here in Thailand are hand dosing your swimming pool.
The salt water chlorinator system is made up of 3 main components. 1/ Salt in the water 2/ Control unit 3/ Salt cell. Salt makes the water conductive so that the electricity can pass between the plates in the cell. If the salt level goes too low, then the chlorine production simply stops. Salt is also the raw material from which the chlorine is produced.
The control unit is a device that sends power to the salt cell. The unit controls how much chlorine is produced by regulating how long the power is applied to the cell. If you turn the control knob way down, then the unit might apply power to the cell only 25% of the time, thereby producing less chlorine. If you turn the control knob up, then the unit would apply power to the cell for a longer period of time. The amount of power applied to the cell does not increase or decrease.
The control unit will often sense the level of salt in the pool and indicate the need to add more salt. Self cleaning units have a feature built into the unit that reverses the polarity of the voltage through the cell in order to clean any scale buildup off of the cell plates.
The salt cell is a series of plates with opposite charges in a cell. As the water passes between the plates, electrolysis takes place, releasing the chlorine in the salt. This is how chlorine is made on an industrial scale but much larger. Salt water chlorinators actually make chlorine gas which passes through the water creating the chlorine level that we read when we do a test.
The beauty of this system is that it only leaves salt as a bi product. Another bonus is that the water balance of a salt pool is easier to maintain. Because the chlorine is set a predetermined level you don’t have the bounce you see in hand dosed swimming pools here in Thailand.
The only thing that is needed is a little acid to bring the pH down as this is normally a bit high because of the salt content. Salt pools will normally run at a pH of 7.8 if acid is not used and the best pH is 7.4 to 7.6. One thing I have noticed in Thailand is that nobody seems to take any notice of the calcium levels in the water.
Water is very aggressive and will seek its own balance if we don’t artificially do it by adding chemicals. One of the first things that water looks for is calcium. If it is low the water will suck it out of the surface of the pool and surrounds. This is why you get sand wash falling apart, tiles falling off and white scale build up around the pool edges.
In Thailand I have found that normally swimming pools have around 50 ppm of calcium in the water, whereas salt water pools have high calcium content, around 150 to 180 ppm. Although 250 ppm is the desired level, you are close, so this means you are protecting the surface of your pool.
I can not believe the number of swimming pools I have seen around Thailand that are only around 1 year old and the surface is deteriorated so much that they need resurfacing. It is hard to get the calcium tested in Thailand as a special reagent is needed and the proper test kits that I used in Oz are hard to get. So by installing a salt water chlorinator system you basically solve this issue.
Salt water chlorinators are easy to fit whether you have an existing pool or you are in planning stages. See you next issue. Steve Johnson is the Managing Director of “WET” Water Engineered Technologies (Thailand) and offers a broad range of “Commercial & Domestic” water filtration solutions, potable water, plus swimming pool design, construction, equipment and consultation.
Steve can be contacted on # 08484 28317 or email email@example.com