I am getting only warm water in upstairs shower but hot water in adjacent bathroom sink. I have read other posts on this subject but just don't know where to start (other than calling a plumber). Had the same problem a month back and it corrected itself within a day. Here is a pick of the faucet: [url=http://flic.kr/p/bktpnX]faucet | Flickr - Photo Sharing![/url] It has a flow control and a temperature control. There is no marking as to manufacturer. I can't seem to figure out how to get the temperature control off the wall or else I'd have taken a picture of the inside setup. Any help would be appreciated - let me know what other info I can provide. Thanks very much.

When I first moved into this house, the bathroom drain was slow. My grandfather lived here before me, and he just plunged it every few days to keep it clear. I have a plumber friend, and he took off the trap and the horizontal drain pipe, and found the pipe in the wall was full of this really hard thick black substance. He used an old screwdriver and a bunch of muscle and managed to clean it all out. Fast forward about 3 years, and the sink got slow to drain. I cleaned out the drain, and he checked the trap, still slow. I asked him to check the horizontal pipe again, and the same substance was building up there. Any idea what this substance is, or what to do to prevent it from building up? We're on a septic system, so I'm not real keen on dumping harsh chemicals down there..Thanks!