Toilets, Sinks, Showers, Tubs and Disposals - Black Smudges in Tub

We have a Kohler whirlpool (K-1375) with inline heater. It is about 6 years old. For a couple years now, we have been noticing small black smudges in the bottom after use. The tub is white acrylic. The smudges act like grease. They smudge more when you rub them.
Scrubbing bubbles does not take them out without alot of elbow grease. I tried an experiment with paint thinner, and they come right out.
I had called Kohler and they said they were mildew from jets and to run bleach and automatic dishwaher soap through tub, which we do every time (per Kohler), but they keep showing up.
Has anyone else heard of this? There are no leaks under tub (I was thinking maybe some gaskets were breaking down). Thanks.
Dave

Sounds like the pump assembly is harboring/leaking out the fine grease out of the shaft of the motor possibly?

Hard to know without seeing it first hand.

My thoughts if I was called out to the situation would be the pump itself, recommending replacement.

That wouldn't exactly go over well knowing the expense involved in such a task.

The second possibility is that after replacement, there will be residual spotting for some time to come until all is clear from the system.

I disagree with the mildew statement from Kohler. Very difficult to deal with and warn of this condition.

I also figured this was something coming from motor. Would this be fixed with a new seal? Motor works fine, and there are no leaks. I looked at Kohler's website, and there are numerous parts available for the motor. The motor is easily accessible, and I am rather handy. Or I could bring it to someone who does repairs.
What would be the eventual result if nothing is done....motor failure (not a big deal) or leakage down into our first floor (Huge deal). Thanks.

Actually, I spoke with someone who repairs/replaces motors. He says that the motors are sealed in such a way that it is impossible to get any type of grease into tub.
He said that it is black algae that has a greasy/ smudgy appearance. The use of bleach will eventually wreck the rubber fittings in the tub.
Has anyone else had an issue with this black algae? What would be the best for treating it....maybe oxyclean?

We're actually talking two types of pumps, but next time you talk to him ask him what happens when a submersible pump overheats and bleeds oil out into the water, contaminating the ground water.


The above situation is a thread posting on another forum I can't link to this site, but it's common.......but isn't directly related to your exact situation.



Since it's speculative at best, knowing it takes a chemical solvent to remove it, I would venture to say that a lab test needs to be done *cheaply as possible* to determine what it truly is.


Home Depot makes a product that is 3-4 steps involving applying the product while in operation, refill and repeat till clear.


The smudges act like grease. They smudge more when you rub them.
Scrubbing bubbles does not take them out without alot of elbow grease. I tried an experiment with paint thinner, and they come right out.