Dec
19
If we were to identify just one part of pool maintenance as the most difficult, we’d have to say it’s maintaining swimming pool chemistry. The quality of swimming often depends on the quality of pool water in fact. And some of these qualities are too dangerous for swimming. This page is intended to help you understand the basics of your pool’s water chemistry and the importance of maintaining a good water balance.
Chlorine Is Only Part of the Equation
First and foremost, understand that maintaining good swimming pool chemistry doesn’t depend on chlorination alone. New pool owners can wrongly make this assumption, but then wonder why their pools are constantly clouding, irritating swimmers, or actually damage the pool itself. Maintaining proper pool chemistry largely depends on pH and alkalinity instead.
pH
Without going too much into a chemistry lesson, pH is a measure of the acid-alkalinity balance in water. It provides a scale that ranges from 0 to 14, where 7 is neutral and greater than 7 is more alkaline (also termed basic) and less than 7 is more acidic. You need to keep an eye on this level because too much acid will corrode metal, eat away at plaster and vinyl, and irritate the heck out of your swimmers! Too much alkali will put scales (calcium deposits) on your pool walls and plumbing, thus clouding the water. Too much of either diminish the effect of chlorination. A perfect pH level for any swimming pool is between 7.2 and 7.8.
Total Alkalinity
While pH is a measure of the balance between acidity and alkalinity, total alkalinity (TA) measures the quantity of alkaline substances alone, regardless of the amount of acid in the water. High levels of TA act as a buffer that prevents fluctuations in the water’s pH. Therefore total alkalinity is also referred to as buffering. The pH level of water that’s too buffered (i.e. high TA) will be difficult to adjust, should the need arise, while water that’s not buffered enough can experience rapid fluctuations in pH levels.
Therefore it is important to keep a proper measure of TA to be able to control the pool’s pH level. The appropriate level of TA for plaster coated concrete pools is between 80 and 125 parts per million (ppm), and the appropriate level for painted plaster, vinyl and fiberglass pools is between 125 and 150 ppm.
When taking care of your pool water chemistry, it is easier to start by fixing the TA levels first, and then proceeding to balance the pH. This is because, good TA will lead to water that has stable, yet readily adjustable pH.
Calcium Hardness
The hardness of water is a term that describes the amount of minerals dissolved in the water. Water is said to be hard if it contains lots of minerals, of which calcium is the most dominant, and soft if it doesn’t.
Too much calcium in the water, i.e. water that’s too hard, contributes to cloudy water problems, high pH levels, and the formation of calcium sales. On the other hand water that’s too soft is very dangerous to the pool systems. It is corrosive to metal pipes, contributes to the softening of plaster and tile grout, and causes cracks in vinyl liners. Swimming pool calcium ion content should be maintained at levels between 200 and 400 ppm.
Not all pool chemistry testing kits include calcium hardness tests, as it need only be tested once at the beginning of each season for a normally used backyard pool. If your kit doesn’t include this test, you can sample your water and get it tested at your local pool shop.
Calcium ion levels can be increased by a adding a chemical such as calcium chloride dehydrate into the water. Lowering the levels is a bit trickier. The most straight forward way to soften the water in your pool is to drain some of your pool out, and add fresh, softer water. If this proves too difficult, a pool professional can filter the calcium out with a nano-filter that can take out the smallest of particles out of the water.
Total Dissolved Solids
Total dissolved solids (TDS) is a measure of the overall quantity of matter in the pool that isn’t water, including minerals, chemicals, body oils, sunscreen, etc. These concentration of these materials increases in the pool as more “stuff” is added to the pool and its water evaporates. This eventually leads to cloudy water, decreased effectiveness of sanitizers, a salty water taste, and a friendlier environment for the growth of algae.
You can test your pools TDS levels with a TDS meter, or alternatively take a sample of water to a swimming pool shop. TDS levels should not exceed 2500 ppm, and ideally they should be under 2000 ppm. To keep TDS levels low, you could treat your pool by regularly adding alum-based clarifiers, such as aluminum sulfate, to the water. These clarifiers work by making small particles stick together and settle to the bottom, where they can be vacuumed out of the pool. A very effective method of keeping your pool’s TDS levels low is occasionally draining the pool a few inches and adding fresh water.
Please note that the salt required by salt water chlorinators will substantially increase the TDS level. Therefore, in salt water pools, it is best to consider the TDS level after the required amount of salt has been added to a freshly filled pool as the baseline level.
Excessively high TDS levels may require more drastic measures such as a complete pool drain and refill, or professional water filtering, as a complete water drain may damage some pools.
