these things are HEAVY. fill and empty while they are in the boat and the boat is in the water.
this is why you need a pump. to fill, pump end goes in the water, other end of hose goes to sac. to drain pump end goes to sac, other end goes to lake.
the atwood 750 that most of the sac manufacturers use is at walmart for 23.00. you just need to go to the hardware store and get a little bit of hose and hose fittings. the hardware store guy will get you hooked up and a cigarette light plug at radioshack and they will tell you how to do it also. use heat shrink butt connectors. do not be antimidated. it is very very easy and about 35.00 or less total. drop me an email if you need any help.