Many spa sanitisers do not perform efficiently if the pH of the water is not maintained within a specified range. So this is a very important issue to monitor.
AquaSPArkle Spa pH Minus is a granular formula. For best results it should be pre-dissolved in a small plastic container filled with spa water.
Add 10g (or approximately 2 teaspoons) of granular product to a litre of warm spa water. Then add the resulting solution to the spa whilst the pumps are turned on. Run the spa for several minutes to ensure the mixture has circulated. The process might need to be repeated more than once. Never mix chemicals or add more than one at the same time.