Always keep your septic tank full of water. Never allow a tank to sit in the ground empty. This unit was pumped one week before Christmas. The property owner and tenant were on site during the pump out and was advised to immediately refill the unit to avoid floatation. This was what we saw when we got the call two days later. This was a very unnecessary and expensive repair that should not have had to happen, and created an unnecessary emergency. Empty septic tanks; concrete and fiberglas can float if left empty in the ground. There is no such thing as a septic tank that is not “full.”