I live in an older 5-story apartment building. The riser pipes which supply hot and cold water as well as the sewage pipe have seen better days. It seems that one of them had sprung a leak, possibly in my apartment. The maintenance guys came and changed a piece, but there's still plenty of old pipe there, just waiting for a chance to rain upon an unsuspecting neighbor.
I'd like to have some sort of alarm in place that would notify me that there's something wet in there. I have easy access to the pipes, so I could just check them every now and then, but... that'll get boring soon and I'll just stop doing it. And if I check them rarely (like once a month) then I'll probably miss the essential moment when things can still be salvaged without needing major repairs in the apartment downstairs.
I'd prefer something low-tech, non-electronic. I pass the place every day, so if I could tell at a quick glance that everything is OK, that would be great. Any ideas?
Here's a picture:
