Swimming pool, Spa and Hot Tub enjoyment will be fulfilled if you regulary test the fundamental parameters of your water:
Chlorine / Bromine
Any chemical will only work and produce the expected results if it is dosed in the correct proportions. What ever the method of dosing you are using to apply the chemicals, you should always back this up with regular testing of the swimming pool or spa water to ensure that the ideal chemical conditions are maintained at all times.
A range of Test Kits is available to enable you to regularly check all the important chemical parameters within your system.