Calcium hardness is a term that measures that amount of dissolved minerals in your swimming pool water. These minerals not only include calcium but magnesium and sodium as well.
In the event the calcium hardness is too high, there's a simple way to lower it by partially draining your swimming pool by using your filter. Pool supply stores have chemicals that help soften the water but can be costly and at times ineffective.
Most pool owners at some time will have to raise their pool's calcium hardness levels as opposed to reducing them. But in the somewhat rare case you have to lower the calcium hardness, also known as softening the water, you must first test the water.
Use a water testing kit or testing strips to measure the calcium hardness levels. Make sure the calcium hardness levels are high, don't assume.
The symptoms of low calcium hardness are shared with other water chemistry properties such as pH and alkalinity.
The cheapest way to quickly lower calcium hardness is to partially drain the pool. Turn off your filter.
Turn the multi-valve port of your filter to the "Drain" setting. Connect a pool hose from the filter's backwash valve to the yard's nearest drain.
Let the filter drain below the pool skimmer. Draining the pool below the skimmer will lower the water about 20 percent for the average 4- to 5-foot-deep swimming pool.
Turn the multi-port valve back to the "filter" setting. Do not turn the filter back on because the water level is too low.
Turn on your yard's water supply and drop your garden hose into the pool to re-fill the pool. Remove the hose nozzle and wrap it around the pool ladder to keep it in place.
Continue to monitor the water to make sure the pool doesn't overflow. The ideal water level when re-filling the pool should be between the half-way and two-thirds point of the skimmer's vertical height.
This water level provides for optimal filter circulation.
Turn your filter on and allow it to circulate the water. Use the water testing kit to retest the water for calcium hardness levels.
The calcium hardness level should be reduced with the addition of new water. Check and balance the other pool chemicals such as chlorine, alkalinity and pH.
Wait 24 hours and monitor the results.
Another Softening Method
Another method by which to lower the calcium hardness is by shocking the pool with lithium hypchlorite instead of calcium hypochlorite, which is the traditional chlorine shock used for most pools. Using the lithium shock will prevent excessive calcium buildup.
Water hardness increases over time if you use too much calcium hypochlorite.