Bottomless Sump Pit

[mekump]

Hello,
I need to replace the sump pump in my parents house which is about 50 years old. I noticed the sump pit 17" wide and 27" deep is concrete on the sides (probably foundation) and the bottom is just dirt. The sump is used only to pump rain water from the outside basement entrance to a spot safely away from the house.
My questions: Should the bottom of the pit be concrete or should I try to install one of those premade Polyethylene basin's? Or, is the bottom of the pit, dirt for a reason? I have not yet bought a sump pump. Are their any particular brands I should stay away from, reliabilty, quality?
Thank you,
Mike

[prashster]

Water is supposed to flow into the pit from the ground so it can be pumped up and out. That's why it's open underneath.
There are 2 problems with this, though. The dirt doesn't provide a stable, level surface for the pump. Also, it increases the chances of dirt getting into the impeller of the pump.

You can get a pe basin, but make sure water has a way to get in. I'd also sit the pump on 2 bricks or something else that is dirt-free, heavy, and stable/level.