Your Guide to Pool Water Chemistry

Your Guide to Pool Water Chemistry

Did you know there are five chemical levels that you should be keeping track of? They include:

1. Free Chlorine – This is a sanitizer that keeps germs out of your pool. You must constantly replenish chlorine.
2. PH – Acidity/Basicity – This must be balanced regularly to protect your equipment and prevent irritation. (7.2 to 8.0)
3. Total Alkalinity – The right levels will keep the pH balanced. High levels will increase pH 50 to 90ppm or higher.
4. Calcium Hardness – The right levels will prevent plaster damage. Levels that are too high will lead to calcium scaling. (250 to 650ppm, vinyl lower)
5. Cyanuric Acid – This protects chlorine from sunlight and will determine the necessary FC level. (outdoors 30 to 60ppm, SWG 60 to 90ppm, indoors 0 to 20ppm)

On top of these, there are four other chemical levels that you should know about:

1. Combined Chlorine – There is a problem if this is over 0.5ppm.
2. Salt – This is necessary if you have a Salt Water chlorine Generator (SWG).
3. Borate – This is an optional enhancement.
4. Phosphate – Removing these can keep algae levels in check.

We will go into all nine here in more detail.

FC- Free Chlorine

Maintaining the right FC level is critical if you want to keep your pool water balanced. If it gets too low, you will get algae. If it gets to zero, or algae appears, the pool becomes unsafe for swimming.

You can increase FC with household bleach, liquid chlorine, and salt water chlorine generators (SWG).

CC- Combined Chlorine

This is created in the process of pool sanitization, and it’s what causes that distinct chlorine smell. If the level is above 0.5ppm, you need to shock the pool. CC usually stays at or near zero provided you maintain an appropriate FC level and the pool receives at least some direct sunlight.

Potassium monopersulfate, which is a common non-chlorine shock, shows up on chlorine tests as CC. You can pick up a special reagent to neutralize the potassium monopersulfate for a truer CC reading.

PH – Acidity/Basicity

This shows how acidic or basic the water is. You should test for pH daily, at least at first. Once you learn your pool and its levels, you don’t have to monitor it quite as frequently. A PH level of 7.6 to 7.8 is best, but anything between 7.2 and 8.0 is fine.

PH levels below 7.2 tend will sting your eyes. If it goes below 6.8, metal parts, such as pool heaters with copper heat exchange coils, can be damaged. High pH results in calcium scaling as well.

To lower pH, use either muriatic acid or dry acid. To raise it, try borax or soda ash.

TA – Total Alkalinity

This is an indication of how well the water can buffer PH changes. With buffering, you have to use more of a given chemical to change the PH. When TA levels are low, the pH tends is unstable. When TA levels are high, the PH increases.

Increase TA with baking soda, but take it slow.

CH – Calcium Hardness

Calcium hardness is basically how much calcium is in the water. Water that has low calcium dissolves calcium out of plaster, pebble, concrete, tile, stone, and fiberglass surfaces. To stop this from happening, make sure the water gets plenty of calcium. If you have a vinyl liner pool, you don’t need calcium. If you have a plaster pool or fiberglass pool, keep calcium between 250 and 650 parts per million. For spas, keep the CH at 100 to 150 to reduce the chance of foaming.

Increase CH with calcium chloride or calcium chloride dehydrate. Lower it by replacing water or utilizing a reverse osmosis water treatment.

CYA – Cyanuric Acid

Also known as stabilizer or conditioner, cyanuric acid protects FC from sunlight while lowering its strength. The higher the CYA level, the more FC you need. This is why you should always be aware of your CYA level. In a non-SWG pool, CYA should measure between 30 and 60ppm. In a SWG pool, CYA should be between 60 and 90ppm.

You can increase CYA with cyanuric acid.

Place solid/granular cyanuric acid (CYA) in a sock either in the skimmer basket or in front of the pool return. After you add CYA, run the pump for 24 hours and don’t backwash/clean the filter for one week. Squeeze out the sock every once in a while to make it dissolve more quickly. Once dissolved, test CYA the day after.

The best way to lower CYA is to replace the water.

Salt

Salt is necessary with a SWG. You can also add it to the water to enhance its texture and feel. You will know the proper salt level by consulting your owner’s manual, usually around 3,000. If you want to improve your water feel without a SWG, go with a level around 2,000ppm. These levels aren’t usually detected by people as a salty taste.

You can add salt using solar salt, which is typically sold for water softeners. It should be 99.4% pure or better. Go with crystals or pellets but just keep in mind pellets take longer to dissolve. Pool store salt is more expensive and more finely ground.

Borate

Borates are an optional way of controlling PH drift and can improve subjective water quality and feel. The recommended level is 30 to 50 ppm.

Phosphate

Phosphates are usually taken out of the pool in an effort to keep algae in check. However, chlorine itself does the job of keeping algae in check, so there’s really no need to spend more money on costly phosphate remover.

Get in touch with Central Jersey Pools if you need help testing and balancing all these chemicals. We can ensure they are at optimum levels at all times for safety and enjoyment.