For an explanation of techical terms, follow the links or see A Layman's Guide to Technical Terms or pH Explained.
What products you use to dose the pool depends on (a) whether you own an outdoor pool or an indoor pool (b) whether you live in a soft water or hard water area and (c) how much time you can afford to look after your pool (high maintenance/low maintenance).
The recommendations on this page take these factors into account. However, because indoor pools are in continuous use year round most of them are fitted with chemical feeders and it makes little sense to preserve the distinction between regular maintenance and low maintenance.
(a) Sanitise the pool with dichlor granules or dichlor with added algicide
(b) Fine tune prior to bathing using the same product(s)
(c) Superchlorinate with calcium hypochlorite granules
OBSERVATIONS:
The calcium hypochlorite will be converted to hypochlorous acid as soon as it is shock dosed and will be a much more effective way of breaking down chloramines than a stabilised chlorine. The calcium will beneficially increase hardness and help prevent corrosion and grout loss.
WARNING: Never mix different types of chlorine before dosing and avoid circumstances where they could meet in concentrated solutions [Technical terms in order of use: Dichlor/ superchlorinate/ calcium hypochlorite/ pH/ Chloramines/ stabilised chlorines]
(a) Sanitise the pool with calcium hypochlorite tablets dosed via a circulatory feeder (the skimmer can be used, but damage could occur in the long term)
(b) Fine tune prior to bathing using dichlor granules
(c) Superchlorinate with calcium hypochlorite granules
OBSERVATIONS: Occasional use of dichlor to raise chlorine levels if necessary before bathing will provide a prompt response and add a little stabiliser to help protect the chlorine from sunlight.
The calcium hypochlorite tablets and granules will assist by raising pH and calcium hardness.
WARNING: Never mix different types of chlorine before dosing and avoid circumstances where they could meet in concentrated solutions
[Technical terms in order of use: Calcium hypochlorite/ dichlor/ stabiliser/ pH/ calcium hardness]
(a) Sanitise the pool with dichlor granules or dichlor with added algicide
(b) Fine tune prior to bathing using the same product(s)
(c) Superchlorinate with calcium hypochlorite granules
OBSERVATIONS:
The calcium hypochlorite will be converted to hypochlorous acid as soon as it is shock dosed and will be a much more effective way of breaking down chloramines than a stabilised chlorine. Using calcium hypochlorite to superchlorinate is a better idea than using dichlor as it will help to keep stabiliser levels within recommended parameters.
WARNING: Never mix different types of chlorine before dosing and avoid circumstances where they could meet in concentrated solutions
(a) Sanitise the pool with trichlor tablets dosed via a circulatory feeder (the skimmer can be used, but damage could occur in the long term. A good alternative would be to use a sealed floating chlorine dispenser such as Fi-BUOY)
(b) Fine tune prior to bathing using dichlor granules
(c) Superchlorinate with calcium hypochlorite granules
OBSERVATIONS:
Trichlor tablets in the skimmer will need replenishing every 2-3 days. Trichlor in a sealed floating dispenser can last for up to 6 weeks.
The calcium hypochlorite granules for superchlorinating will break down chloramines quickly without adding to stabiliser levels.
WARNING: Never mix different types of chlorine before dosing and avoid circumstances where they could meet in concentrated solutions
[Technical terms in order of use: Trichlor/ dichlor/ calcium hypochlorite/ hard water/ pH/ stabiliser/ chloramines]
(a) Sanitise the pool EITHER with calcium hypochlorite tablets through a specially designed feeder, OR bromine tablets. On balance, the recommendation would be calcium hypochlorite.
(b) Fine tune prior to bathing by increasing or reducing water flow through the feeder by means of the control valve or electrical controller.
(c) If sanitising with calcium hypochlorite tablets, superchlorinate with calcium hypochlorite granules
OBSERVATIONS:
Calcium hypochlorite on the other hand contains no stabiliser. It will counteract the tendency for the pH to fall in a soft water area and the calcium will be particularly helpful in achieving satisfactory water balance.
The case for bromine tablets (BCDMH, or bromochlorodimethylhydantoin - sorry about that one!) is that bromine is less dependant on pH for optimum performance. The product is promoted on the basis that it creates a more comfortable atmosphere in the pool building than chlorine based products (though this is a matter of opinion!), and is slightly less harmful over the longer term to fixtures and fittings in the building.
WARNING: Never mix different chemicals or types of or chlorine before dosing and avoid circumstances where they could meet in concentrated solutions
[Technical terms in order of use: Calcium hypochlorite/ bromine/ superchlorinate/ stabilised chlorines/ stabiliser/ pH/ soft water/ water balance]
(a) Sanitise the pool EITHER with bromine tablets (BCDMH) through a feeder, OR calcium hypochlorite tablets. On balance, the recommendation would be bromine tablets.
(b) Fine tune prior to bathing by increasing or reducing water flow through the feeder by means of the control valve or electrical controller.
(c) If sanitising with calcium hypochlorite tablets, superchlorinate with calcium hypochlorite granules
OBSERVATIONS:
Although it is not uncommon to find calcium hypochlorite used in indoor pools in a hard water area (it is very widely used in sports centres), it could require quite a bit of attention to keep the pH down to recommended levels.
WARNING: Never mix different chemicals or types of or chlorine before dosing and avoid circumstances where they could meet in concentrated solutions
[Technical terms in order of use: bromine/ calcium hypochlorite/ pH/ hard water/ hypobromous acid/ hypochlorous acid]
For those with the time to give the pool regular daily attention:
The dichlor will provide sufficient stabiliser to prevent wasteful loss of free chlorine to the uv in sunlight, without increasing the tendency for the pH to fall.For those who do not have the time to give the pool regular daily attention:
Calcium hypochlorite tablets can last for up to a week in one of the more recently developed off-line feeders and they should keep the pool in good order in the absence of day to day supervision. Alternatively, pelletised calcium hypochlorite can be dosed via the skimmers, but will need more frequent replenishment.
[Technical terms in order of use: Dichlor/ calcium hypochlorite/ pH/ hypochlorous acid/ chloramines/ stabilised chlorine]
For those with the time to give the pool regular daily attention:
The dichlor will provide sufficient stabiliser to prevent wasteful loss of free chlorine to the uv in sunlight, without raising the pH.For those who do not have the time to give the pool regular daily attention:
Trichlor tablets being mildly acidic should act as a useful corrective to the tendency for water in hard water areas to increase in pH. Using trichlor as the main sanitiser means stabiliser levels will not be increased as quickly as with dichlor which need only be used occasionally if the free chlorine level before bathing is below 1.5ppm.For ongoing pool maintenance:
It does not make too much sense to use stabilised chlorine products in an indoor pool unless water replacement/backwashing can be kept at a sufficiently high level to prevent build up of stabiliser (cyanuric acid).For ongoing pool maintenance:
The three factors in favour of bromine are (a) if the pH strays upward, as it is likely to in a hard water area, you get a much higher percentage of active sanitiser at high pH values (at pH 8.0, you get 83% hypobromous acid (HOBr) with bromine but only 24% hypochlorous acid (HOCl) with chlorine). Also, (b) some bathers find the atmosphere in the pool building or enclosure more pleasant with bromine than with chlorine. Finally, (c) bromine is probably slightly less harmful over the longer term to fixtures and fittings in the building.
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Pool Owners Guide: [Basic poolcare] [Problem solving guide] [Topical tips]
Technical Section: [Technical terms defined] [pH explained] [Balanced water test] [Recommended products]
Buy Your Own Pool: [The reasons people do] [The choices, the costs]