Pavers for equipment ?

The equipment when full of water will be very heavy. Water weighs about 8lb. per gallon. Settling will be a problem for sure if you don't put down a substantial foundation layer regardless of the mounting surface. Even the concrete mini-slabs my builder used have shifted since they just threw them on the ground. Skip the rubber.
 
I have concrete pavers that are a foot by a foot. They were compacted down with pea gravel and sand first to make the ground very firm. I then have a 500lb sand filter on top of them and they have not moved a bit. The pump sits just fine with 2 unions that allow for some minor movement for the pipes. Look in my signature as I do believe there is a picture of the pad that I reconfigured a few years ago when I bought the house.

Concrete slab always works best in my opinion. Bolting them down is not necessary, but to help eliminate sound, you could use a product called flex seal on top of the slabs. Its a rubber product that sticks to the concrete and helps absorb some of the vibration and noise from the pump. I did it and it works great.
 
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