Updated- end of thread,something in the black tank.

The Magnet idea might work but test it at a RV store first juse use a fridge magnet on the thing.

I suspect the wire in the hose might be ferromagnetic (Will be attracted) but the spinner is most likely brass (pairomagnetic) and will get excited if a magnet passes by but won't be attracted (Excited is a physics/engineering joke,, A magnet passing a non-magnetic hunk of metal "Excites" and electrical current).