Wasps in the well pump.

We’re on city water, but when they switched the house over the owner at the time attached a manual water pump to the well.  Its decorative, but it DOES work, and we try to keep in in repair as a backup water source. 

We’ve been a bit neglectfull this year, and didn’t use it till a couple weeks ago.  And sure enough the wasps have made a nest inside the thing (yes its wasps, not the hornets with the giant nest, thankfully).  We’ve tried drowning the nest, repeatedly, but they just keep coming back.  Needless to say this is not a spot where wasp spray is a good idea.

Any ideas as to how to get rid of the nest or are we stuck till it gets cold?