What SPA chemicals are needed to prepare for lots of relatives using the tub, and what can be done after? Last time 5 people used the hottub, the chemicals go out of...

Last time 5 people used the hottub, the chemicals go out of balance. Someone told me I could pretreat the SPA and posttreat to toy with this temporary overload. What should I add on?
Moving out detail... append to it please?
Answers:    Bromine tablets and shock treatment. If you need a touch extra chemical shock you can grind up a couple of bromine tablets in a blender and sprinkle it around the tub while the jet are on. Hose out your filter really good and or you can also soak your filter is TSP (Trisodium phosphate) for a few hours to seize all of the oil out of it then hose it stale really good.