Not all Chlorine is Alike
||Although we do not recommend packaged chlorine as a primary sanitizer in the hot water of spas, one type
Granular Chlorine 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)
Dichlor is the only packaged chlorine form suited for spas because although it is a little more expensive, it has near-neutral pH and does not require the addition of cyanuric acid stabilizer. 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
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.
A Better Way to Chlorinate Hot Tubs: Salt Systems
Saltron Mini is an easy to install plug-in system for hot tubs, which automatically produces pure chlorine from mineral salts.
Swimming pool owners have enjoyed the many benefits of saltwater purification systems for years. This revolutionary new chlorine generator makes salt technology practical for spas. Nexa Spa is an affordable plug in system which is simple to install, without any modifications to the spa itself.
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. It requires the addition of cyanuric acid to keep it stable in sunlight. Without stabilizer, it can lose 95% of its effectiveness in just a couple of hours. Due to its high calcium
component and high pH level, 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. It is one of the most caustic forms of chlorine on the market, so avoid it in spas. If
you are going to use chlorine, sodium dichlor is well worth the few extra
pennies in weekly cost.
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.
bleach can easily splash on surrounding surfaces, including your spa
cover, and may cause permanent damage. Bleach
also reduces filter life when used for cleaning.
Combined, and Total Chlorine
Chlorine in spa & pool spa water may be present in two forms. First, Free Chlorine does the job of killing bacteria and oxidizing contaminants. When you add chlorine to the water, you are adding Free Chlorine. When the Free Chlorine
reacts with contaminants such as oils, bacteria and other organics, it becomes combined chlorine, or chloramines. Unlike combined bromine, combined chlorine has little sanitizing ability, and no oxidizing ability.
Chloramines also have an irritating odor. Combined chlorine is like a spent bullet. Chloramines have a harsh odor, and can cause
red eyes and irritation. (You'll have less chance of
these problems if using bromine and can avoid them
altogether with an
+ Free Chlorine = Total Chlorine
Therefore, if the total chlorine level is higher than free chlorine, that indicates the
presence of combined chlorine. In that case you need to shock or superchlorinate your pool or spa. Shocking with
non-chlorine MPS shock, or dichlor in an extra large dose will actually oxidize the combined chlorine and destroy the chloramines.
You can test and measure Free and Total Chlorine with our
7-in-1 Test Strips.