Learning About Your Pool’s Water Chemistry

As a pool owner, it is imperative to learn how to keep your water properly balanced. If you are diligent about testing your pool water, you will be rewarded with clean healthy water, keeping your swimmers safe. If you are not careful, you will face many problems, not only with water, but also with the surface of the pool, (ie: marbledust) as well as pool equipment such as the plumbing and heater. So be sure to learn how to properly care for your pool water to protect your investment.

There are five factors that affect water balance: pH, Total Alkalinity, Calcium Hardness, Total Dissolved Solids (TDS), and Temperature. If any one of these levels are off, not only will the swimmers most likely experience eye and skin irritation, you will also see cloudy or green water, algae growth on the floors, and walls of the pool, metal corrosion, and plaster etching. You can test the water with a test strip kit or a liquid test kit.


You will also need to know how many gallons your pool holds. Below is a guide to help you determine how many gallons your pool holds based upon measurements.

Click Here For A Useful Pool Volume Calculator

pH –
Water pH is a measure of acidity or alkalinity. The pH scale runs from 0 – 14 with 7 being neutral. Lower values are acidic, and higher values are alkaline. The acceptable range for pool and spa water is 7.2 to 7.8 parts per million (ppm). This is also known to be the comfortable range for the human eye, which is one reason why it is important to make sure the pH is balanced. Acidic water (low pH) will cause eye and skin irritation. Acidic water will also dissipate chlorine levels. If the pH is too low, it will also cause etching in plaster and metals. Adding an alkali (sodium carbonate) will increase the pH. You will also find products called pH Increase or pH Up.

When the pH is too high, the water is alkaline, also called scale producing. Alkaline water will be cloudy, and will form scale deposits on the floors, and walls of the pool, and equipment. You will need to add an acid such as muriatic acid or sodium bisulfate. You will also find products called pH Down or pH Decrease. As with low pH, High pH levels will also cause skin, and eye irritation. It will also dissipate the chlorine. Most of the chemicals you will be adding to the pool are either acidic or alkaline, and will affect the ph level.

Total Alkalinity –
Total Alkalinity is the sum of all the alkaline substances in the water. The acceptable range is 80-120 ppm. Maintaining proper alkalinity will stabilize the pH level as well. If the Total Alkalinity is too low, marble dust will become etched, staining will occur, the water will turn green, and or cloudy, metal will corrode, and swimmers eyes will burn. To increase the total alkalinity without increasing the pH significantly, you can add sodium bicarbonate.

If the Total Alkalinity is too high, the chlorine will lose its efficiency, water will become cloudy, and pH is difficult to balance. Acid can be used to lower the Total Alkalinity.

Calcium Hardness
Calcium Hardness is the measure of the waters calcium content. The ideal range is 200 – 400 ppm. Too much calcium in the water causes the calcium to precipitate out of the water and will create “calcium deposits” on the walls, floors of the pool, and even the circulation system. If the calcium is too high, it is best to replace some of the water with fresh water. It is more common for the water to have a lower calcium level. Low calcium hardness leads to plaster, concrete, and grout damage, if this is the case, pre-dissolved calcium chloride can be added.

Total Dissolved Solids (TDS) refers to the concentration of conductive chemicals, bather waste, and other solids that accumulate in the water. Even though you cannot see these solids (because they are dissolved), they will corrode pool equipment such as pipes, pumps, and filters). TDS should not exceed 1,500 ppm.

TDS is more of a concern for spas, as opposed to pools due to the evaporation level being higher in the spa. The simplest way to lower TDS is to replace some of the water with fresh water.

Temperature –
The ideal temperature for pool water is 78 to 82 degrees while a spa should not exceed 104 degrees.  Temperature can significantly affect water balance. When water is consistently above 90 degrees, scale formation can develop. To prevent these problems, water should be tested more frequently.

Chlorine –
Chlorine is the most popular swimming pool sanitizer. Different types of chlorine will have different effects on the waters pH level. Pools with a high pH level will require higher levels of chlorine to kill off algae, and bacteria. The chlorine will dissipate more on a hot, sunny day. For this reason Chlorine should be paired with a stabilizer. (Cyanuric acid). Liquid shock can be added, and slow dissolving tablets can be kept in the skimmer basket, or chlorinator.

Chlorine readings should be 1 – 3ppm.

Chlorine Stabilizer 30 – 50 ppm

Algaecides –  Algaecides are used to kill and prevent Algae from growing in the pool or spa. The most common algae is floating green algae. However there is also black and yellow/mustard algae.  It is important to use the proper algaecide to treat the type of algae your pool may have.