ichthyoid;543074 wrote: As for check valves, they are an added potential point of failure-IMO. I have used one (a very good expensive design) and never felt comfortable with it. I prefer simple 'self draining' overflows. That way if the pump stops, the water stops. No overflow onto the floor. Except for the already mentioned plugs from algae balls, snails, etc, vitually foolproof.