I'm looking to purchase a cordless shop vac primarily for cleaning drain lines. Dewalt offers a couple. One is a 1/2 gallon capacity and the other is 2 gallons and can be used either corded or not. Does anyone have either of these? Are they strong enough? Currently I have a "Stinger" corded Vac and would like to switch to a cordless as long as I don't lose power. Any input is appreciated.