Waykar - 80 Pint Dehumidifier with Bucket and Auto Defrost 5,000 Sq. Ft. Energy Star for Bedroom and Basement - White

It won't directly connect to the unit itself, not. The drain hose is quite a bit smaller O.D. than a garden hose. You may be able to rig it where the hose that comes with the unit drains into the garden hose and is then gravity fed where you need it to drain.

Gravity

It has what looks like a very basic filter for incoming air. In my opinion it is not HEPA

Yes, it holds a lot of water. It ran for 10 hours before I had to empty it.

This one doesn't have a pump. it's gravity drain or empty the bucket. But there is a bigger 150 pint version that has a built-in pump, might wanna check that one out