Quick Point:
Check your plumbing traps. There is a reason they are called traps and they harbor nasty things.

Get a bucket, unscrew the pipes, drain it and scrub it with a bottle brush and diluted bleach. Your bathroom, kitchen and other places will smell much better.

How I found out about this:
I am not necessarily a clean-freak but when I clean a bathroom and it still smells musty, I wonder why.

For some reason, I decided to check the drain of the bathroom sink. It had an old toothbrush in there - yes I have kids.

I couldn't get the brush out so I had to get a bucket, unscrew the drain trap and pull out the brush.

When I unscrewed the pipes and pulled out the trap, it was full of stuff - all black. It had hair, small toys and string. Needless to say - it didn't smell too good.

The insides of the PVC white-colored drain pipes were black and had a thin layer of black on all the pipes.

I got a bottle brush and scrubbed the inside of all the pipes with bleach and water (diluted 1 part bleac...