Literature - Calcium - Watermaid SA, Suppliers of Salt Water Chlorinator for Swimming Pools and Spas

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Calcium

Question is - when using the cell in summer, with heavy use of the solar, where the pool temperature gets above 20 Centigrade, is it unusual that calcification occurs at such a level that acid treatment of the cell is necessary every week to ten days ?

Calcification in cells is a function of three things (at least)

The calcium level. Any level above 120 ppm will show calcification An ideal level would be 60 to 90 and you would only find that in SYDNEY and MELBOURNE if the water is straight from the tap and went into inert surface such as a fiberglass pool and you did not use powdered chlorine (Calcium hypochlorite)
The rate of calcification increases dramatically as the water temperature rises as you have indicated. You notice very little calcification in the middle of winter.
As the pH rises above 7.6 the rate of deposition (or calcification also increases.)

Q. Isn't monthly acid treatment of the cell about normal ?

I would have thought a monthly cleaning treatment a little excessive Our attitude is that you only clean the cell when the deposit stops the cell from making sufficient chlorine. That would be about when the cell current drops below 10 amps (or 10 GRAMS OF CHLORINE EQUIVALENT per hour)

More importantly the cell must be cleaned if the deposits build up to a stage that it touches or impinges on the Platinum electrode that never shows a deposit formation (i.,e, the anode)

To allow the deposit to cover that electrode blocks the chlorine gas formed from dissolving in the water. Chlorine gas in contact with titanium will etch it and the baked precious metal coating will flake away... shortening the life of the cell.

Before adding acid to the pool you really should do the acid demand test. i.e,,e, how many drops does it take to bring the pH to the 7.6 range. If it is 1 or 2 drops leave the pool alone.

Once upon a time the test kits used to say... if the chlorine level is greater than 1 ppm do not test for pH with the water. Chlorine levels of that order change the phenol red dye to a deep purple and the pH reading is not true. I always suggest do the acid demand test and if only 1 or 2 drops leave the pool alone if it is clear and clean and has a chlorine reading.

Q. I might just be running the filter too long as well - I am doing it up to to full days at a time then 8 hours. Should I expect this shorter time between need for cleaning the cell in this hot weather ? am I running the filter, is it the price to pay for a balmy pool at night, or is something else wrong ?

The present run of hot weather for the last six weeks is more than we have seen for the last 8 years.

Swimming pool practice demands that all the water pass through the filter 1 to 1 1/2 times each 8 hours and that 1 ppm of chlorine be put into the pool. Your chlorinator can make 1/2 to 1.5 ppm of chlorine for the water flow... so it need the 8-10 hours running per day.

In winter at 5-7 degrees C 1 - 2 hours running a day would be fine but not summer.

Just remember run the pump and filter 24 hours a day and a thimbleful of chlorine would probably be sufficient OR put a bucketful of chlorine in and run the pump 1 hour a day.

Both ways you will wind up with a clean pool. The optimum cost effective way is 8 hours filtration and 1 ppm of chlorine added.

Finally what to do about the excessive scale deposit.

We recommend the use of 5 to 10 Kg of Epsom salts be added (Magnesium Sulphate from the local nursery) Magnesium in the water will not stop the deposits from forming but what does form will have a soft slushy texture and the chances are that the water flow will be sufficient to flush most cell deposits away to be caught on the filter.