I'm about to clean out the drains. (You know, it's true what they say. The fun never stops at Chez Escargot.)
The kitchen sink is blocked. I blame it on the drought. Very little of the water that goes into the sink exits through the drain. Most of it gets scooped out and distributed on the increasingly crisp garden vegetation. The grot concentrates and settles in the pipe. (I think that's what happens. I'm no plumber. But the plumbers that plumbed my house don't appear to have been plumbers either, so we're all in the dark.)
I'm going to try bleach first. But if that doesn't work I'll have to dismantle the pipes.
I may be some time.