As a owner of a Hot Tub Spa -
Before we use the "Whirlpool Bath" - we fill the tub with water that is only hot enough for the hand to handel, (WARNING) the hot water at VWL surpasses scolding temp's and its a long wait for the water to cool down before you can reach that @2 foot deep drain plug (I learned the hard way last year - the 2 seconds was enough)
2nd, Wife and kids goto pool - since we buy bleach for our laundry anyway we pour about 1/2 gallon of Ultra Clorox into filled tub and run for @ 15mins. We do this not only to clean but also to disinfect any leftover water that always remains in the pump and jet lines from previous room users. Also, open the patio/balcony door/doors to introduce fresh air into the room - which is recommended when using cleaners.
Last is to re-rinse the tub at least 2x filling the tub to just above the jets to clear the lines of bleach and running the pump both times for a few minutes.
Yes the room will have a "left over" bleach scent (look for a scented bleach - helps a little) but thats why the family went to the pool and your soon to follow.
kda - I was relaxing in it and then noticed brown scum on the water line
kda, the brown scum you noticed is either sweat, lotions or deoderants from a previous user or yourself. The brown scum is even more noticable when the air valve introduces bubbles into the water - the scum particles "attach themselves" in turn rising to the top of the water and when it pops - the scum clings to the fiberglass tub causing the "scum line". It is the same problem as in a Hot Tub Spa but is easily lessened considerably by simply having users shower prior to using the tub - Pain in the a**? Yes. But its a lot nicer opening your eyes after 20 min's and not saying "WHAT IS THIS STUFF ALL OVER ME ?!?!?!?" and taking that shower anyway.
Enjoy that stress relieving whirlpool bath!!