showerbug

If the shower writes "empty pipe" then it doesnt get enough incoming water and thats why it doesnt work. (need a steady flow of water with liquid valve or a 10kg blob waiting at inlet)

If the shower writes "not pumping" then it can pump out the contaminated water. In the save file and the above pictures you used pipes with cross sections. Every cross section halves the right so send out blob even if the pipe is empty. (Either you have to use single line outlet pipe into a vent or purifier, or use liquid valves to maintain the outlet pressure)

I've noticed a similar thing, but it's not a bug. If you link together two outlets, and the waste from one passes through the other, it can register as being currently full in the other one. Happened with me and linking a shower with a toilet - the moment the dirty water passed the toilet, any dupe using it would get ejected and the flush animation would play, until the water passed.

Not a bug. This is due to pipes's behaviour.
1. Can the contaminated water extract from the shower fast enought? (may need a few tiles long before next intersection as a buffer).
2. Is there enought water comming in? Same, you might need a small water buffer. 

may be a bug :

• Faced with intersections, inputs and outputs have a hard time to do theyr job. Water in OnI will only flow in one direction at a time.