Calcium Hardness in Pools: All You Need to Know

Calcium hardness refers to the amount of dissolved calcium and magnesium in the water. The water collects these minerals as it passes over soil and rocks along its journey from its source to the tap. The hardness level of water depends on the type of rocks and soil it flows over. For instance, water flowing over limestone, which contains a large amount of calcium, results in hard water. The water needs a minimum of 150 ppm of hardness to maintain balance and prevent it from becoming aggressive or corrosive.

The term “hard water” originally referred to water in which soap does not produce much foam or suds due to the presence of mineral salts. Trying to create lather with soap in salt water is a difficult process due to the characteristics of hard water. Nowadays, water hardness refers to the amount of dissolved calcium and magnesium in the water.

What is Calcium Hardness in chemistry?

In chemistry, calcium hardness refers to the amount of dissolved calcium and magnesium in water. The water absorbs these minerals as it travels over soil and rocks. The presence of calcium and magnesium in the water results in what is known as “hard water”. The hardness level of water varies depending on the type of rocks and soil it flows over. For instance, water that flows over limestone, which contains a large amount of calcium, will result in hard water. On the other hand, water that flows over granite, which contains minimal calcium, will generally result in softer water. Under certain conditions, this soft water is also more corrosive, or ‘aggressive’.

How does Calcium Hardness relate to the Saturation Index?

Calcium hardness is one of the key factors used in the calculation of the Saturation Index (SI). The SI is a mathematical equation developed to predict a specific water’s tendency to form calcium carbonate scale. Calcium and magnesium are essential in water to prevent it from becoming aggressive or corrosive. The water needs a minimum of 150 ppm of hardness to maintain balance. For plaster pools, the target calcium hardness is 350 ppm, while for other materials like vinyl, fiberglass, and acrylic, the target hardness level is 250 ppm.

What is the importance of Calcium Hardness for pool water?

Calcium hardness is crucial for pool water as it prevents the water from becoming aggressive or corrosive. The water needs a minimum of 150 ppm of hardness to maintain balance. When the water lacks sufficient calcium, it increases the chance of dissolution of plaster pools or the metallic parts of the equipment. On the other hand, excessive hardness leads to scaling, depositing a hard white or off-white crusty material on tiles, heaters, and pool walls. Therefore, maintaining the right level of calcium hardness is essential for the longevity of the pool and its equipment.

What determines the ideal hardness level of pool water?

The ideal hardness level of pool water is determined by the type of pool surface. For plaster, exposed aggregate, and tile pools, the target calcium level is 350 ppm. For vinyl, fiberglass, acrylic, and other non-calcium based porous surfaces, the target is 250 ppm. The minimum calcium hardness level for pools is 150 ppm. In areas where the source water contains high levels of calcium and magnesium, it is necessary to use this hard water but make appropriate adjustments to its pH and total alkalinity levels.

How does calcium saturation vary and what are the target levels?

Calcium saturation in a pool varies based on factors such as pH, total alkalinity, temperature, and total dissolved solids (TDS). The minimum calcium hardness level for pools is 150 ppm. For plaster, exposed aggregate, and tile pools, the target calcium level is 350 ppm. For vinyl, fiberglass, acrylic, and other non-calcium based porous surfaces, the target is 250 ppm. In areas where the source water contains high levels of calcium and magnesium, it is necessary to use this hard water but adjust its pH and total alkalinity levels accordingly.

How often should we check the hardness level in a pool?

While the hardness level in a pool does not increase rapidly, it is recommended to check the calcium hardness every three months. Additionally, the tap or source water must also be tested before draining to determine its hardness level.

What causes low Calcium Hardness in pool water?

Low calcium hardness in pool water is caused by the use of source water that lacks sufficient calcium. When the water does not have a minimum amount of calcium to reach saturation, it becomes aggressive or corrosive, attempting to dissolve any available source of calcium or magnesium. This often leads to the dissolution of plaster pools, as plaster is made from calcium. In non-plaster pools, aggressive water starts to dissolve the metallic parts of the equipment.

What are the effects of low Calcium Hardness in pool water?

Low calcium hardness in pool water leads to difficulty in balancing water, etching of plaster, corrosion of metal components, eye and skin irritation, and foaming. When the water lacks sufficient calcium, it becomes aggressive or corrosive, attempting to dissolve any available source of calcium or magnesium. This often leads to the dissolution of plaster pools, as plaster is made from calcium. In non-plaster pools, aggressive water starts to dissolve the metallic parts of the equipment.

What are the signs of low Calcium Hardness in the pool?

The signs of low calcium hardness in a pool include the water becoming aggressive or corrosive, attempting to dissolve any available source of calcium or magnesium. This often leads to the dissolution of plaster pools, as plaster is made from calcium. In non-plaster pools, aggressive water starts to dissolve the metallic parts of the equipment.

What are the consequences of swimming in a pool with low Calcium Hardness?

Swimming in a pool with low calcium hardness leads to difficulty in balancing water, etching of plaster, corrosion of metal components, eye and skin irritation, and foaming.

When the water in a pool lacks sufficient calcium, it becomes aggressive or corrosive. This leads to the dissolution of plaster pools, as plaster is made from calcium. In non-plaster pools, the aggressive water starts to dissolve the metallic parts of the equipment. This causes eye and skin irritation for swimmers. Additionally, the water becomes difficult to balance, leading to issues with water clarity and cleanliness. The water also starts to foam, which is unappealing and affects the swimming experience.

Is low Calcium Hardness level in the pool water dangerous?

Yes, low calcium hardness level in the pool water is dangerous.

Water requires a minimum amount of calcium to reach saturation. Without it, the water becomes aggressive or corrosive, attempting to dissolve any available source of calcium or magnesium. This often leads to the dissolution of plaster pools, as plaster is made from calcium. In non-plaster pools, aggressive water starts to dissolve the metallic parts of the equipment. Therefore, maintaining a minimum calcium hardness of 150 ppm is essential to prevent the water from becoming aggressive or corrosive. The target calcium hardness level is 350 ppm for plaster pools and 250 ppm for pools made of other materials like vinyl, fiberglass, and acrylic.

How to increase Calcium Hardness in the pool?

To increase calcium hardness in a pool, calcium chloride is used. Specifically, adding 14.4 ounces of 100% calcium chloride or 19.2 ounces of 77% calcium chloride to 10,000 gallons of water raises the calcium hardness by 10 ppm. When the calcium hardness is near the target level, adjustments to total alkalinity and pH are to be considered. If the calcium hardness is low, the amount of calcium chloride needed to reach the target must be calculated. The target calcium hardness level is 350 ppm for plaster pools and 250 ppm for vinyl pools.

How to achieve Calcium Hardness balance in pool water?

To achieve calcium hardness balance in pool water, the water must be tested first to determine its current hardness level. If the calcium hardness is low, it is increased by adding calcium chloride. If the hardness level is high, it is decreased by partially draining the water or using a chemical that lowers hardness. The target hardness level is 350 ppm for plaster pools and 250 ppm for vinyl, fiberglass, and acrylic pools. It is recommended to check the calcium hardness every three months.

What happens when there is too much Calcium and Magnesium in the water?

When there is an excessive amount of calcium and magnesium in the water, it becomes oversaturated and deposits the surplus in the plumbing, equipment, or pool vessel. These deposits are known as scale. When the water has the potential to create these deposits, it is referred to as scale-forming.

Excessive calcium and magnesium in water lead to a number of issues. The oversaturation of these minerals causes them to deposit in the plumbing system, potentially leading to blockages and damage. This is particularly problematic in pool vessels, where the deposits, known as scale, build up on the walls and equipment. The water’s ability to form these deposits is often an indicator of its hardness, with harder water being more likely to form scale.

What happens when water has too much hardness?

When water contains excessive hardness, it begins to deposit or precipitate the excess amount it is no longer able to hold. This process is known as scaling. The hard white or off-white crusty material on tiles, heaters, and pool walls is scale. High hardness levels also cause the water to become cloudy.

What are the effects of high Calcium Hardness in pool water?

High calcium hardness in pool water increase the risk of scale formation on the vessel and equipment, cloudy water, eye and skin irritation, and difficulty in balancing the water. When the water contains excessive calcium, it becomes oversaturated and deposits the surplus in the plumbing, equipment, or pool vessel, a process known as scaling. This results in hard white or off-white crusty material on tiles, heaters, and pool walls. Additionally, high hardness levels cause the water to become cloudy.

What are the consequences of swimming in a pool with high Calcium Hardness?

Swimming in a pool with high calcium hardness leads to scale formation on the vessel and equipment, cloudy water, eye and skin irritation, and difficulty in balancing the water.

Is high Calcium Hardness in the pool dangerous?

No, high calcium hardness in the pool is not dangerous. However, it causes issues such as scaling and cloudiness in the water.

How to Correctly Test for Calcium Hardness in Water?

The correct way to test for calcium hardness in water involves a process of titration, typically using ethylenediamine-tetraacetic acid (EDTA). The first step is to eliminate any interfering magnesium in the water. This is done by increasing the pH using a base reagent, usually sodium hydroxide. The second step involves introducing a color indicator to the water sample, which changes its color from light red to sky blue as the titrant gradually mixes in. The third step is to add EDTA drop by drop until a determined endpoint, when the color of the solution has completely changed from light red to sky blue, is reached. The number of EDTA drops used is then multiplied by a calibration factor, usually 10, to determine the level of calcium hardness. Good lighting conditions while performing the procedure are crucial for accurate results.

How to lower pool Calcium Hardness?

When the calcium hardness level in a pool reaches 500 ppm, it is advisable to drain a portion of the pool water to reduce the hardness. An alternative method to lower calcium hardness chemically involves the addition of trisodium phosphate. This substance reacts with the calcium in the pool water, forming fine white particles that cloud the water. These particles are a precipitate that must then be removed by vacuuming or filtering.

What are the effects of Calcium Hardness on pool water quality?

Calcium hardness significantly impacts pool water quality. High calcium hardness leads to scale formation on the vessel and equipment, cloudy water, eye and skin irritation, and difficulty in balancing the water. On the other hand, low calcium hardness causes issues such as difficulty in balancing water, etching of plaster, corrosion of metal components, eye and skin irritation, and foaming. Therefore, maintaining the right level of calcium hardness is crucial for maintaining pool water quality.

Calcium hardness refers to the amount of dissolved calcium and magnesium in the water. If the hardness level is too high, the water begins to deposit or precipitate the excess amount it is no longer able to hold, a process known as scaling. This results in a hard white or off-white crusty material on tiles, heaters, and pool walls. If the water lacks sufficient calcium, it becomes aggressive or corrosive, attempting to dissolve any available source of calcium or magnesium. This leads to the dissolution of plaster pools or the metallic parts of the equipment.

The calcium hardness level in a pool varies based on factors such as pH, total alkalinity, temperature, and total dissolved solids (TDS). The minimum calcium hardness level for pools is 150 ppm. For plaster, exposed aggregate, and tile pools, the target calcium level is 350 ppm. For vinyl, fiberglass, acrylic, and other non-calcium based porous surfaces, the target is 250 ppm.

In the process of evaporation from a pool, it is only the pure water that evaporates, leaving behind the dissolved solids, which include calcium and magnesium. Over time, these dissolved solids, including hardness elements, accumulate in the pool. As additional water is introduced to the pool, the hardness also increases, especially when the added water has a high hardness level. Consequently, hardness levels in the pool keep increasing. Therefore, it is important to closely monitor the pH, total alkalinity, and water hardness levels.

What Happens When Calcium Hardness Levels are Inappropriate?

When calcium hardness levels are inappropriate, several issues arise. If the water contains excessive hardness, it begins to deposit the excess amount it is no longer able to hold, a process known as scaling. This leads to the formation of hard white or off-white crusty material on tiles, heaters, and pool walls, and causes the water to become cloudy. On the other hand, if the water lacks sufficient calcium, it becomes aggressive or corrosive, attempting to dissolve any available source of calcium or magnesium. This leads to the dissolution of plaster pools or the metallic parts of the equipment.

Inappropriate calcium hardness levels also inhibit the process of balancing the water, cause eye and skin irritation, and lead to foaming. High hardness levels cause scale formation on the vessel and equipment, while low hardness levels lead to etching of plaster and corrosion of metal components. Therefore, it is important to regularly check the hardness level in a pool, ideally every three months, and aim for a calcium hardness of 350 ppm for plaster pools and 250 ppm for other materials like vinyl, fiberglass, and acrylic.

What happens when water lacks sufficient calcium?

When water lacks sufficient calcium, it becomes aggressive or corrosive, attempting to dissolve any available source of calcium or magnesium. This often leads to the dissolution of plaster pools, as plaster is made from calcium. In non-plaster pools, aggressive water starts to dissolve the metallic parts of the equipment.

What is a Scale?

A scale refers to calcium carbonate deposits that form on surfaces in contact with water that has high calcium hardness.

How to Balance Calcium Hardness and Total Alkalinity?

To balance calcium hardness (CH) and total alkalinity (TA), first the CH is checked. When the calcium hardness is near the target of 350 ppm for plaster pools or 250 ppm for vinyl, adjustments to the TA and pH are made. When CH is low, calcium chloride is added. When CH is more than 400 ppm, the water is typically mixed or replaced. Then, TA and pH are checked. When TA is 80 to 100 ppm and pH is 7.4 to 7.6, no adjustment is needed. When TA and pH are low, sodium bicarbonate or soda ash is added. When TA and pH are high, acid must be added.

Balancing these parameters necessitates regular testing. For alkalinity, if the sample shows one of the two total alkalinity color indicator reagents, follow the manufacturer’s instructions to eliminate the excess chlorine. For calcium hardness, the test first involves increasing the pH using a base reagent. Next, a color indicator is added to the sample. Finally, EDTA is added drop by drop until the endpoint, a noticeable change in color, is observed.

How does Calcium Hardness impact pool water balance?