Here's another view of the switch hole positioned 1" below the level of the inlet.

Comment for the documentation ... you may wish to tell people why you have this requirement. I figured out that when you turn the water off a fair amount of water still flows down the tubes until everything settles down. I guess that's why the 1" requirements, to accomodate that additional water flow.

One thought for the system would be an "empty out" switch or button that one could manually turn on the pumps to empty out mufflers. Just a thought.