If your pools calcium hardness level drops below the recommended 150 ppm the easiest and most common way to raise swimming pool calcium hardness is by adding a calcium hardness increaser such as calcium chloride to your swimming pool.
Low calcium levels will ruin your pool's alkalinity. This will, in turn, corrode metal items. Your pool's railing and mechanical parts could become damaged. Thankfully, it's easier to raise water hardness than lower it.
However, adding too much baking soda might also raise the PH level of your pool to an undesired stage (alkaline). In the case where too much baking soda is added to hard water, it can cause a build-up of calcium around your pool.
Low Calcium Levels in the Pool
Low calcium, as is often the case, will cause long-term serious damage especially to plaster, vinyl liners, grout in between tiles, metal rails, and even concrete decking around the pool. Here's why it happens. Plain old water, believe it or not, is very aggressive.
You can raise water's calcium hardness easily by adding calcium chloride (CaCl2). Two forms are sold: hydrated (77% strength) and anhydrous (100% strength). Each will generate heat when contact with water is made.
Baking soda, also known as sodium bicarbonate is naturally alkaline, with a pH of 8. When you add baking soda to your pool water, you will raise both the pH and the alkalinity, improving stability and clarity. Many commercial pool products for raising alkalinity utilize baking soda as their main active ingredient.
Hardness is the sum of the multivalent metal ions in solution, whereas alkalinity is a measure of the solution's ability to neutralize acids (sum of hydroxide, carbonate, and bicarbonates). In natural water systems calcium carbonate is usually present and responsible for different characteristics of the water.
As a caution do not add more than 10 lbs of calcium chloride per 10,000 gallons of pool water at one time. It is wise to wait at least 12 hours before adding any more calcium chloride to the pool.
A low hardness level can lead to corrosion of the pool surface, filter, heater, ladder, etc. Likewise, if the water is too soft(low calcium level) you are also more likely to experience problems with algae. A calcium hardness level that is too high can cause cloudy water and scaling (a white chalky appearance).
In theory, if you have a cloudy swimming pool, you can add chlorine to “shock it” and clear things up. Chlorine will get the job done. But, the amounts may vary and you may have to really pound the pool with chlorine to get the water totally clear.
What can you use instead? Bromine — considered a safe substitute for chlorine. Looks for BCDMH tablets, which are typically 66% bromine and 27% chlorine. If unable to find, you can use just bromine but it may leave the water a dull green color.
Most balancing chemicals, such as pH, alkalinity, and calcium hardness, will become incorporated into the water within an hour of adding them, at which time swimming is safe. Shock takes longer to adjust with the pool water, so waiting overnight after shocking before you swim is recommended.
Calcium hardness is also very important to the chemical balancing of your vinyl liner swimming pool. Calcium for a liner pool can be a bit lower than a plaster pool, in the range of 150-250 ppm.
It's usually just a temporary reaction as the sanitizer works its magic, and doesn't always indicate a problem. But if the cloudy water persists long after you've shocked the pool, you're likely having an issue with water balance, circulation, or filtration.
Such interaction produces a toxic gas that is dangerous to health even in small amounts. A good rule of thumb is to never mix pool chemicals with each other. After adding Calcium Hypochlorite a user should always wait 24 hours before adding chemicals that would alter their pH.
If, for example, you add too much of a calcium supplement, you will drive down alkalinity as you get precipitation of calcium carbonate in the tank. Likewise, adding too much of an alkalinity supplement can result in reduction of calcium.
Alkalinity and Calcium Hardness in Daily Operations
Optimal range for alkalinity is roughly between 60-120 ppm. Just remember, the higher you go, the harder time you will have affecting change on your pH, in either direction. Calcium hardness should be kept at 250 ppm minimum.
In addition to raising available chlorine, cal hypo boosts pH, alkalinity and calcium hardness (CH) levels. Trichlor has the opposite effect on pH and alkalinity — reducing it. And where cal hypo affects CH, trichlor increases cyanuric acid (CYA).
It's safe to swim immediately after adding, but you should turn on your pool's circulation system to help it dissolve.
The good news is, baking soda is a simple, safe way to help maintain water quality in your pool, keeping your water clear, sparkling, and pleasant to swim in, without drying the skin or stinging the eyes.