Tipping the carpet cleaner is neither necessary, customary, nor expected. Same with your plumber. Especially if they own their business...you should never tip the owners. Skilled service workers that come into your home are paid a decent wage or salary, plus, often commission per job. They do not expect a tip. However, if they are prompt, courteous, do a wonderful job or exceed expectations (do extra work at no charge), it is a nice gesture to tip them a flat $10 or $20, and it is appreciated. But again, not necessary. Now, waitresses and delivery people...hairdressers and other folk who depend on tips as part of their earnings (they don't even get minimum wage), they should always be tipped according to performance 10, 15, or 20%. Beyond that, I just tip when I feel it is the right thing to do. I recently tipped the AAA guy that came out to service my car that wouldn't start. The only thing he was required to do was to jump-start my car or tow it if it wouldn't start. He spent a good 30 minutes evaluating my vehicle for the cause, found the problem, fixed it, and saved me a couple hundred dollars that a mechanic would have charcged me. I tipped him $20, and he was very surprised and appreciative. I was so glad I did... my car has run perfect ever since.