White deposits in a cell are normal and are a by-product of the generation of chlorine by the cell.  The white deposits that build up in the cell are calcium.  The most common cause for the calcium is from the products that you put in the pool.  Granular shock is about 1/2 calcium.   Chlorine pucks that some people use to supplement chlorine production are about the same.  The biggest contributor is usually the addition of calcium directly to the pool.  Often people go to the pool store and are told that the calcium hardness of the water is too low and they are sold a pail of hardness up, or calcium chloride, hardness+ or some other brand name, but the bottom line is, you are sold the calcium that plugs your cell.


Before you get the wrong impression, the pool store isn’t trying to plug up your cell and destroy it.  They simply buy into the North American myth that the calcium hardness of your water needs to be between 200 and 400 or your pool will fall apart.  The notion is, that if the water is too soft, it will take the hardness from concrete walls and metals in your pool.  They base the notion on a a pretty smart guy (Langelier) who figured out how to keep expensive steam train boilers from deteriorating from the high heat and pressure of a closed boiler.  The high heat and pressure quickly deteriorated the cast iron boilers but he found that if you added calcium to the water if prevented this type of corrosion.


Fast forward to about 40 years ago and they came out with these new fangled things called pool heaters which had cast iron headers and thin walled heat exchangers.  Someone got the bright idea that Langeliers calculations would work on swimming pools so they started adding calcium to pools.  Instead of doing the proper calculations someone also decided that you should just keep the calcium level between 200 and 400.  That’s like saying every time make a drink, add a cup of sugar.  That works for a pitcher of lemonade.  Not so good for a shot of scotch.


I’m not opposed to balancing of water and the use of a proper calculation but its original purpose was for closed systems with high heat and pressure.  It works for modern boilers and cooling towers but I am of the opinion that pools are a different critter all together.  If you don’t have a salt water system the arbitrary 200 to 400 number doesn’t cause any problems.  When you add a salt water system, whos’ purpose is to generate chlorine and as a co-reaction pull metals (including calcium) out of the water, you do have a problem


This is why we encourage people to use magnesium in their Watermaid pools.  It adds hardness without using calcium.  We get it in two forms.  Epsom salt (magnesium sulphate) which is what we use in Canada and magnesium chloride which is the better product but it is difficult to find in a clean form in Canada.  It is good for you and good for your pool so in this case I go against my rant about the arbitrary addition of chemicals to a pool and say simply add 50 lbs every spring.


Magnesium makes any calcium deposits that do form mushy like tooth paste and they tend to flush off of the electrodes reducing the number of times a cell needs to be cleaned.


When you do clean your Watermaid cell, I recommend that you simply remove the centre tube and scrape off any deposits or use a rag to crumble them off.  The centre tube is made from titanium so it is okay to use metal scrapers or rough materials to clean it.  The mesh on the inside of the cell if electroplated with precious metal so DO NOT scrape this part or you will damage the plating.


Cell cleaning solutions containing muriatic (hydrochloric) acid tend to be too strong and can etch the precious metal coating of the cell and damage it.  If you do use one of these solutions mix 50% cell cleaner with 50% water and use it that way.