Water Care Academy

Very little, on purpose. The short list of what belongs in hot tub water, the long list of what people are tempted to add and what each one does, and how to get scent and a sense of occasion at the water's edge without putting anything in it.

Cold water needs less sanitizer and more attention. Bromine dissipates faster from hot water into freezing air, top-ups arrive cold and hard, strips misread in the cold and pH climbs. The winter routine for water that stays in, and the one rule that ends a season.

Stop feeding it and let it fall, dilute, or neutralize in small steps. Then find out why it climbed, which is almost always a dispenser set for a busier week than the one you had.

No. Epsom salt is magnesium sulfate, and a bath-sized dose in water that is held for weeks raises dissolved solids, unbalances the sanitizer, foams, attacks metal and voids most warranties. What it does, what to do if it has already gone in, and how to get the same effect without it.

Water circulates to spread heat and to carry every gallon past the filter and the sanitizer. Without a pump, convection and a paddle do it. With one, a short loop runs on a schedule: out through the filter, past the heater, back through one return. How each works and why it matters.

Empty the tub after every soak and you skip sanitizer entirely, because the water never sits long enough to need it. What fresh-fill owners still do, why it works on a tub with nowhere for water to hide, and when holding water starts to make more sense.

Both sanitize. Chlorine is cheaper and faster; bromine is stable in hot water, works across a wider pH range and smells far less. For an aluminum hot tub the choice is made for you. How each works, and why chlorine and aluminum do not mix.

Both are sold as a way to use fewer chemicals, and both do real work. But almost nobody explains what they are compensating for, which makes it hard to judge whether you need one.