White, chalky, rough feeling on the walls or floors of your pool – this is build-up also known as scale. The longer the scale is on the wall the harder it is to remove. pH
The most fragile and arguably the most important component of water balance is pH, a reading that indicates how acidic or basic the pool water is. The pH of the water has a definite effect on the efficiency of chlorine as well as on the corrosive properties of water. Free Chlorine is most efficient at 7.2 – 7.4, combined chlorine is useful but not in high amounts and is what causes the chlorine smell.
Ionized pools pH ideal range is 6.9-7.1 to keep water balanced.
Water that is not balanced – too acidic (lower numbers 6.9 or basic higher numbers 7.6) – can cause swimmer discomfort, cloudy the water and cause damage to the pool or pool equipment. Properly balanced water or saturated water prevents damage to the pool and equipment. Unsaturated water (acidic) corrodes fiberglass walls, fixtures, plumbing, etc. This also causes metal staining. An oversaturated water (basic) deposit scales (calcium) or becomes cloudy.
High pH Indications Poor Sanitation of water Cloudy water Shorter filter runs Calcium scale formation Skin and Eye irritation
Low pH Indications Poor sanitizer efficiency Etched or stained walls Corroded metals/equipment Skin and Eye irritation Destruction of Total Alkalinity
In addition to the effects of pH on chlorination process, it also affects the total alkalinity of water. This plays a major role in the degree of calcium carbonate saturation (hardness of water).
Total Alkalinity
Is a measure of the pH-buffering capacity, or the water’s resistance to a change in pH. This ability to resist change in pH is due primarily to the presence of the family of carbonate ions, but certain other compounds also provide buffering.
Alkalinity is a pH “stabilizer”. It keeps the pH within the proper levels so that the chlorine can work effectively. The Level should be between 80-140 ppm for pools and 80-120 ppm.
High Total Alkalinity Hard to change pH Scale Formation Cloudy Water Skin and Eye Irritation Poor sanitizer efficiency
Low pH Indications Rapid changes in pH or “pH Bounce” Stained, etched or break down of gel coat Corroded metals/equipment Skin and Eye Irritation
The relevance to pH is that the amount of alkali (hardness) in the water will determine how easy it is for changes in pH to occur.
If the alkalinity is too low (below 80ppm) there can be rapid fluctuations in pH – for example there is insufficient ‘buffer’ to the pH. High alkalinity (above 200 ppm) will result in the water being too ‘buffered’ – it will make it difficult to adjust or correct the pH.
The carbonite ions have a special role in water saturation. The operator must control both the amount of carbonate alkalinity and the pH to provide enough calcium carbonate to saturate the water without having so much that scale forms.
Total alkalinity and pH are related to water balance because, at low-pH (acidic) conditions, all the carbonate ions are converted to bicarbonates. There is no calcium carbonate formed and water becomes aggressive to the pool walls and equipment. At high-pH (basic) conditions, too much carbonate is formed and even the smallest amount of calcium ion present precipitates, causing cloudy water or scale to form. At normal pH conditions(7.2-7.4) most of the carbonate ions are in the bicarbonate to provide buffering.
Water Hardness
Water hardness is a concentration of the calcium and magnesium in the pool and spa water. This is dependent on your water source.
Calcium hardness is the amount of dissolved calcium (plus other minerals, magnesium) in the water. If you see calcium scaling up the pipework or surface of the pool IT IS NO LONGER DISSOLVED and there for you have too much calcium. Too little could lead to the water satisfying its appetite for calcium by taking it from your grouting.
Like pH and alkalinity, calcium hardness affects the tendency of water to be corrosive or scale forming. The calcium carbonate will precipitate (drop out) of the water and adhere to pool walls.
The acceptable max calcium hardness depends on the amount of total alkalinity needed for pH buffering. If a particular pool tends to change pH rapidly, high total alkalinity (over 100ppm) is needed. Calcium hardness should not exceed 400-600ppm, depending on the pH and temperature of water.
Below are the products that can help remove, solve and prevent scale: Natural Chemistry Pool Perfect, 4 Liter – doheny.com Pure Enzyme for Pools which is a monthly treatment can be found at waters choice. Amazon has Pure Ascorbic Acid powder that will help remove scale for around $20 a bag.
If the scale is calcium silicate, there is no fix. It will not remove from the walls unless ground off and the pool will need to be refinished. Seek a professional refinishing company.
This write up has been provided by San Juan Pools and can be downloaded here.