32 oz. Grout Cleaner and Brightener (Case of 4)

Yes, this product is a whitener and cleaner. I love the results I obtained on my project.

I just poured it direct and used a toothbrush to scrub

No, it cleans whatever it comes in contact with

It is recommended to use on the floor surfaces, and for a good reason. It's an acid, and if applied to the walls, it will run & can damage the metal fixtures on the wall and even can damage the floor if it's not ceramic.

First, there is no "removing it". The acid has a chemical reaction with the surface of some metals (e.g. stainless steel, chrome, etc.) that etch the surface, usually making it darker in color, often in spots anywhere the liquid lands. I learned the hard way (although the package clearly warns). I now mask off any metal anywhere close to where I am working with tape & plastic for a waterproof barrier. How to mitigate? I used Barkeeper's Friend POWDER with a Brillo pad (fine steel wool) & a lot of elbow grease that removes the top layer of metal, back down to a bright shiny surface. You can see some fine scratch marks close up, but the color is what is most noticeable. Your experience may vary & depends on the metal & thickness of the coating. If its chrome plated, you will probably end up seeing some of the underlying brass or whatever it is plated on. Stainless steel is typically solid metal, but can also be rather thin depending on the application. Bottom Line: It will (probably) never look the same, but it can be made to look better.

In my prior answer I forgot to address the septic tank part. In general, you do not want to use significant amounts of sanitizing type chemicals (Chorox, chlorine, etc.) with septic tanks as it tends to kill the "good bacteria" in the tank that breaks down waste. But this product is fairly weak and the small amount you will flush down the toilet cleaning it is no worse than anything else you might use (e.g. Lime Away, CLR, etc.). However, if you are cleaning a tile floor you may have much large amounts in the waste you mop up. So that you may want to find a way to dispose of differently.

I have a colored grout on my floor too. In between deep cleanings the grout tends to have a lighter look to it due to absorbing liquid from mopping, spills, etc. Once I use this product it removes that film and my grout is much darker. This is normal

Yes absolutely

One bottle does about 700sq ft of 12x12 tile with .25” grout lines.

It will clean the tile also