Posted by on Monday, December 19, 2011 Under: Pool Water Chemistry
Alkalinity is the amount of alkaline salts (carbonates, bicarbonates and hydroxide ions) present in the pool water. It is an important factor in the treatment of swimming pool water because it acts as a pH buffer. If your alkalinity levels are too low, you may find it difficult to control the pH level; when you add and acid, the pH level will drop too fast, then when you try to correct the problem, the pH level will shoot up past the level you want it at. If your alkalinity levels are too high, you will have the opposite problem and may find it difficult to budge the pH level. Recommended alkalinity levels are as follows:

When using sodium hypochlorite: 120 - 150mg/l
When using calcium hypochlorite: 80 - 120mg/l

The usual way of measuring it is to collect a 100ml of pool water and add the total alkalinity tablets one at a time and shake. The colour will start off yellow, when it turns bright red (take a look at the picture), multiply the number of tablets you needed by 20 and then minus 10. Example: 5 tablets to bring about the bright red colour (5 x 20 = 100 - 10 = 80). You could also use a 50ml sample (as in the picture), but you would need to multiply the number of tablets by 40 and then minus 20. 

There is a very handy calculator on the 'Tools' section of the website which will work all of this out for you - all you have to do is enter the number of tablets used for a 100ml sample and the calculator does the rest.

In : Pool Water Chemistry 

Tags: "alkalinity" "ph" "buffer"