Not all Chlorine is Alike

Although we do not recommend chlorine as a primary sanitizer in the hot water of spas, one type Dichlor Granular Chlorine #CA1011 is very good for occasional shocking and is a quick-dissolving form.

As a conventional sanitizer, bromine in tablet form is easier to use, with less odor.  Not all chlorine is the same-- we'll explain the differences below.

Sodium Dichlor Granular Chlorine (granular spa shock)

This is the only chlorine form suited for spas.  It is primarily recommended as an occasional shock, since it is not available in tablet form, as bromine is.  It is neither excessively acid nor alkaline in character, and does not quickly deplete at higher water temperatures.  If you use dichlor, the quick-dissolving fine granular formulation is the best.  Avoid the large pellets as they take too long to dissolve, and any particles resting on the spa bottom can cause finish damage.  Since Dichlor is not made in tablet form, if you choose to use it as a sanitizer, more frequent doses and testing will be required than with time-released bromine tablets or some other sanitizer system.

It is best to dissolve dichlor in a bucket of clean water first, then add to spa water.  (Pouring granules directly into a spa can sometimes cause acrylic surface discoloration from direct contact). Never mix different spa chemicals together; always add them one at a time.

Trichlor (pool tabs)

A form of chlorine, trichlor, is excellent for pool water treatment, and is usually supplied as tablets.  We do not recommend this type of chlorine for spas because it has a higher acidic nature, and generally dissolves too slowly to be effective.  Prolonged contact with the spa shell can result in bleaching of the color and may even mark it, sometimes causing a permanent ring at the water line.

Cal-hypo (calcium hypochlorite)

This type of chlorine is popular for pool use because it's relatively cheap.  Due to its calcium component it tends to form deposits on spa heater parts and plumbing fittings, and may also leave an unattractive film or ring at the hot tub's water line. Avoid it in spas-- if you are going to use chlorine, sodium dichlor is well worth the few extra pennies in weekly cost.

Sodium Hypochlorite (household bleach)

Do yourself a favor, and keep household bleach away from your spa!  Not only is bleach a poor sanitizer at higher water temperatures, it readily affects pH balance and tends to have a much harsher chlorine odor.

Avoid household bleach!