Blue stains contained by tub from a dripping thump, how to remove them? ...

My homebuilder is putting a 3 horsepower Zoeller...
Answers:    Spray with Muriatic Acid. It's available at most Hardware Stores, close by the Tiles and Grout.
Just spray and let it sit a few minutes; consequently wipe away. It shouldn't require any scrubbing.
I don't close to Powder Cleaners because they scratch and dull the Finish on your Bathroom Fixtures. Besides, you own to scrub those, it's more work lol.
What is a right method to check if...
Try a powder cleanser called hotel keeper Friend...It comes within a container like comet cleanser...you can receive it at Walmart, Family Dollar, any where...works great.