What is Calcium Hypochloite
Calcium Hypochlorite (Cal-Hypo) is a granular form of chlorine that adds both chlorine and calcium to your pool. For every one part per million Free Chlorine that is added using Cal-Hypo another 0.71 parts per million of Calcium is also added to the water.[1]
You will get a roughly 6-7ppm rise in CH for every 10ppm FC added using cal hypo. Cal hypo also raises pH because it is a very alkaline substance (contains calcium carbonate and calcium hydroxide as a byproduct of the manufacturing process).
Cal-Hypo is commonly sold in one pound packs or fifty pound buckets at major pools stores.
Side Effects of Calcium Hypochlorite
While Cal-Hypo can be beneficial to those with soft water, the Calcium Hardness(CH) buildup should be monitored over the long term. In time if the CH level is allowed to buildup it could cause scaling on the walls of a pool or in the cells of Salt Water Generators. Additionally Cal-Hypo can cause cloudy water if to much is added at once.
Adding Calcium Hypochlorite
Adding Cal-Hypo to a pool is more of a process than adding Liquid Chlorine. Additional steps need to be taken to avoid damaging your pool's surface. To add Cal-Hypo a user should:
- fill a five gallon bucket roughly 3/4 of the way full with pool water.
- measure the amount of Cal-Hypo needed to increase your pools Free Chlorine level to the desired level using PoolMath and add that to the bucket of water.
- mix this water thoroughly until all the Cal-Hypo is dissolved.
- pour that solution SLOWLY into the water in front of your return with the pump on it's highest setting.
- brush the pools surface immediately to make sure all Cal-Hypo isn't sitting on the pools surface.
- vacuum the Cal-Hypo up immediately, if any is found on the floor, to avoid damaging the surface of the pool. Do NOT allow it to sit on the floor and dissolve.
Cal-Hypo Safety Cautions
While you can use cal-hypo as a substitute for liquid chlorine, it is a good reminder to treat it carefully. Cal-hypo can come in several different concentrations (% available chlorine) with 74% often easily obtainable. The downside to cal-hypo is that it emits chlorine vapors even in dry form and those fumes can act as a source of oxidation which can cause fires if flammable substances are stored near it. There are plenty of documented reports of cal-hypo fires happening but we rarely hear about them.[2]
Of particular concern is that people will use cal-hypo but not use it appropriately and open themselves up to exposure. Most cal-hypo for retail consumer use is sold as 1-lb bags of dry powder (and the bags are perforated so that they can breathe/emit chlorine fumes). If you use cal-hypo, the correct way to use it is to use an entire package and not leave any opened but partially used packages lying around. Doing that is a recipe for disaster.
So, if you plan to use cal-hypo in your pool this season, please do so safely by following all labelled package instructions. Also, make sure you store any cal-hypo in a safe location where it can not easily get wet and keep it stored away from any flammable substances.
- Do not put cal-hypo tablets in floaters or chlorinators that were used for trichlor or dichlor tablets
- Do not mix calcium hypochlorite in solid form with other pool chemicals including other chlorinating agents.
- Do not consolidate partially empty packages as this could result in dangerous mixing with incompatible dry chlorinating agents having a similar appearance.
- Calcium hypochlorite can oxidize metals, which may produce contaminants that can stain pool and spa surfaces.
Chlorinator cap exploded describes what happened when cal-hypo was added to a Trichlor tablet feeder. It also has more discussion about cal-hypo safety and chemistry.
.
