Pipe II is being filled by adjacent Pipe III, but there is no connection

Describe the issue
For some reason, my sewage pipe is being filled by the adjacent water pipe even though there is no connection, which is hurting my people. The pipe in question is connected to a balancer and I checked in case there was water coming into there, but the only other pipes connected are two intake pipes, both with waste water in them.

Expected behavior
Pipes not connected shouldn't mingle

To Reproduce
Steps to reproduce the behavior:

1. Load attached save
2. Remove products from the outlet pipe connected to the pipe balancer, going to the waste water treatment plant.
3. Observe how it fills with water again.

Additional context
Version 0.4.1e

Attachments
Save:
bugged pipe.save

Where it is

Pipe in question

Balancer

In Pipe 1

In Pipe 2

Pipe Spaghetti

Files not imported: bugged pipe.save

This is caused by the selected pipe (which is your water output from your Wastewater Treatment) being fed into your wastewater line.