Im thinking of buying a Liberty SJ10 water powered sump pump.

There are few things stopping me.

The water inlet to the pump takes a 3/4" sharkbite. I don't have a 3/4 pipe conviently located around the sump pit. The inlet would have to be 1/2" then I would have to have increase the size off the 1/2. Is that not acceptable? The installation instructions does not mention this.

Also the configuration of the pump doesn't seem to work with a cover on the sump pit. I need to keep the pit covered because of odor.

read the instructions and/or call a plumber

sometimes things are difficult and/or cost money

Water powered sump pumps work from the venturi effect and require a high dynamic line pressure.
edit-deleted all the really boring stuff

Ok, So the pump requires 30 psi of dynamic pressure. The easiest way to check this would be to use 2 outside hose faucets to get a good idea. Put a pressure gauge on one, then open the second all the way and see what your pressure at the gauge is. If it is still at least 50 psi, then you should be fine; At 30 psi, the specs indicate that it should remove 12.8 gallons per minute of water and it will be drawing 1 gallon for every 2 pumped. This means that you have to be able to supply 6.4 gpm at a minimum of 30 psi, and the area that water will be pumping out to needs to be able to handle 19.2 gallons per minute and carry it away from the foundation.

Recognize that you also need a reliable source of water. Meaning if on a well and the electricity goes out unless you have a backup generator you'll be SOL and (as I believe you already recognize) you need plenty of volume and water pressure.

If you have a choice for sure go with a minimum of 3/4" pipe all the way.

Going with 1/2" part of the way might be an issue as in all cases pressures and volumes fluctuate no matter what size pipe and 1/2" is stretching it.

specs and a lot of info:

[www.plumbingsupply.com]

FYI: From my experience this water powered sump pump is pretty reliable.