How does the Cistern work?

[Bulbatron]

I've just finished my second playthrough. I was able to turn one of the valves twice - but not straight away. I too couldn't get past the bridge that was held upwards connected to the chain.

I got all the various effects whenever I turned a valve. So some for the first valve, some for the second valve and then the fleshy stuff and the water lurker for the second valve again a bit later.

Don't quite understand what's going on there. The commentary seems to suggest that we are supposed to turn three separate valves - excluding (I assume) the one which controls the steam.