Wet the surface area of the spa you will be cleaning, work the cleaning Solution (undiluted) in with a sponge, rubbing stubborn deposits more.
Leave for a minimum of 10 minutes, rinse the surface area with plenty of Spa Water. Rinse the sponge with plenty of fresh water.
The great thing about this product is that you can use it while your spa is full. Sometimes your pH may drop slightly as a result as it is slightly acidic but other than that it is a very useful product that is specifically designed to clean your Spa without risk of damaging the acrylic.