Single vs double suction
Why the biggest water pumps take water in from both sides at once.
⏱ 5 min
- Everyday comparisonStep 1 of 5
Two doors are better than one
A crowd leaving a concert hall through one door pushes and shoves. Open a second door on the other side and everyone gets out faster and calmer.
A impeller does this for water: it opens an entrance on both sides.
- Try itStep 2 of 5
One entrance or two
Compare the single-suction impeller (water from the left only) with the double-suction one (water from both sides).
The double-suction impeller is really two impellers glued back to back, sharing one outlet.
- ExplainedStep 3 of 5
Twice the flow, gentler entry
With two eyes, the impeller can take twice the flow at the same speed of water entering each eye.
Slower entry keeps the pressure at the eye from dropping too low. That protects the pump from — damaging bubbles you will study in Module 5.
- ExplainedStep 4 of 5
It balances itself
A single-suction impeller has low pressure on its eye side and high pressure on its back. So it is pushed along the shaft — — and its must hold that push.
A double-suction impeller is symmetric: the two sides push equally in opposite directions and cancel out. Less load on the bearings, longer life.
- The impeller connectionStep 5 of 5
The giants of the water world
Double-suction pumps usually sit in a “split case” that opens like a clam shell, with the shaft supported at both ends. They move water through city water mains, cooling systems and irrigation schemes.
The cost: a bigger, more complex casing. For small pumps, single suction is simpler and cheaper.
📌 Remember this
A double-suction impeller takes water in from both sides: it handles twice the flow, lets water enter more gently (less cavitation risk) and balances its own axial thrust.