What does 'Flooded Suction' mean?

With regards to pond and water feature pumping, the term ‘Flooded Suction’ refers to the inlet of the pump (the suction point) being constantly flooded with water by gravity.  Most pond pumps require a flooded suction scenario as they cannot suck water uphill into the inlet (i.e. the pump cannot pull a vacuum).  So, whilst the pump may be able to be mounted on dry land, the inlet and pipework must be set below the pond water level so water is always entering by gravity.

Swimming Pool Pumps (‘Self-priming’ Pumps) can pull water into their inlet (i.e. positive suction), but self-priming pumps tend to be far more costly on energy consumption than more energy efficient, dedicated pond pumps.  If your pumping system is running 24 hours/day, always try to use a flooded suction pump for this reason (and they tend to run far quieter too).