Air Pump Units

[copps321]

Why do all the higher air pumps have 4 outlets instead of the just 1? I don't really want 4 air stones around the tank and surely just blocking them off means you loose some of the power/air coming out of the 1 outlet you would use?

 

[dgwebster]

typically its because you are running bigger items with multiple input point or multiple items/tanks.
 
If you want to combine them, 1 way valve each output and then join with T-pieces.