Whirlpool Surface, Jet & Line Cleaning
Like a swimming pool, whirlpool tubs need extra care in order to work well. To clean the surface of the tub, use a mild, nonabrasive liquid bathroom cleaner and a soft cloth. Do not apply an abrasive household cleaner; it could scratch the surface. Check all cleaning labels to be sure the products are safe for your tub's surface. (Please check out the many cleaners suggested in the "Shower, Tub and Whirlpool Surface Care" section on this website.)To keep the pump running smoothly, many manufacturers suggest avoiding oil-based bath soaps or additives such as bubble baths, because the whirlpool action will intensify the foaming properties of these products, and the residue could stick to the plumbing. (That is probably what you are seeing coming out of your jets in brown or black flakes!) Use a small amount of low-foaming bath salts instead.
The internal piping of your whirlpool must be cleaned regularly in order to reduce build up of bath residue (from body oils, dirt, soaps, shampoos, or lotions) from the tub's internal plumbing system. A thorough cleaning should be performed weekly even if you only use the whirlpool as a soaking bath without using the jet system.
It is recommended to use the following clean and purge procedure at least every week, if the tub is used daily, or every third use, if used intermittently or occasionally.
1) Fill the tub with hot water until the water line is above the jets.
2) Add 4 tablespoons to 1/4 cup of a low-foaming powdered dishwasher detergent (or gel packets or broken up tablets) plus a few ounces of bleach.
3) Turn off the air induction and run the pump for 10 minutes and then drain the tub.
4) Refill the tub with cool or warm water and run the pump for 5-10 minutes and drain.
There are also commercial cleaning products made specifically to do this job. A few are listed below: