Promising review: "I just spent two hours scrubbing the ceramic tile floor in my second bathroom. This is a room where my elderly, incontinent cat lives so... use your imagination. I leave pee pads and towels down, but she still does her thing. I clean her room consistently, and every few months I do a heavy duty scrubbing by soaking the floor and grout in Nature's Miracle and start scrubbing. It takes hours because I can't get the corners well, and the grout is such a pain to clean. Well, this product is amazing. I used this for the grout lines, and I used the corner attachment for... corners. It was amazing. It got gunk and grime off the grout that has been there for years (I haven't resealed this floor since it will have to be taken out when the cat dies). I even used these to scrub the cabinet doors, around the toilet, etc. and they were really, really great. you have to put the right amount of pressure on the brush, but once you do, it's *wonderful.*" —None
Get it from Amazon for $19.