I have used a Bridge connection to separate sewage from clear water in my pipelines. It works just fine when the showers and toilets are in use. But when the system should be idle, the water keeps pumping from the resevoir and it seemingly dissapears at the bridge pipe connection. The water on one side is full. But the bridge connection keeps swallowing water for no apprant reason, becoming a nasty waste of water.
EDIT: Fix Found. Seems like reloading the game fixes this bug. So whenever you make a bridge connection, save and relog to stop it wasting water.
Simply make a plumbing system that includes a bridge connection on the clear water intake (towards the toilet, shower, etc.) and when the water pumps through, let the water fill up on one side of the bridge. The water will keep pumping into the bridge as if its never filled.