Can you put a inflatable pool on top of a leach field ?

Leach fields work by percolation and evaporation. Compressing or covering that area is not a good idea.  NOBODY should ever run "heavy equipment" over a leach field or even drive or park ordinary vehicles there.  Technologies change over time, so we can't guess what sort you might have, but the simplest ones are just perforated drain pipes under the frost level.  If your frost depth is 4 feet or more, you can't break the pipes by driving over them, but you can still damage the evaporation by compressing the topsoil unnecessarily.

Modern leach fields work by evaporation as well as ground absorption. Not the best idea to cover it up. There is no stench as one idiot suggested.

https://howtosquirrel.com/10-reasons-why-do-leach-...

The stench will be a problem and covering the leach field will also prevent it from working properly

over the leech field will be ok.  it is perfectly capable of supporting multiple people walking on it at the same time, so 1700 pounds plus people spread out over the footprint of the pool [what counts is ground pressure per square foot] is fine.  -- grampa

If a 200 lb. man walking in your yard doesn't make it sink, the relative weight of the pool distributed over a large area shouldn't be a problem. The perforated arms on a septic system are wrapped in mesh and embedded in sand. Heavy equipment installed and rolled over it. 

My blood is eaten by a leech