Dr. David G. Williams writes that a Texas A & M University microbiologist recently did testing on 43 different drain-after-use whirlpool baths and found that
95% contained fecal bacteria 81% harbored fungi 36% had the same bacteria that causes Legionnaires' Disease
It appears that whirlpool tub water is over 19,000X more toxic than tap water!
Williams suggests that there are ways to sanitize the pipes and jets to prevent the re-circulation of this bacteria and fungi after you drain your spa.
I would also say think twice about using the whirlpools in hotel rooms!
~extracted from the pre-publication edition of "The 50 Dumbest & Deadliest Medical Myths in Your Mailbox"