Welcome to our forum.
One other question. Do you need to let the water cool down before you drain it?
What do you recomend for the sanitizer?
Bromine was probably the most preferred way to sanitize a spa at one time, even by the manufacturers. Who ever said it would void a warranty had to have some misinformation.Now trichlor in a floater will void almost every manufacturers warranty.
Some warranties (Dimension 1 for example) state that the use of slow dissolving sanitizers will void the warranty ( among other things). This would include any puck, chlorine or bromine. Other manufacturers do not prohibit any puck, including trichlor.