What is an impeller?
The spinning wheel inside almost every pump: what it does, in one picture.
⏱ 4 min
- Everyday comparisonStep 1 of 5
The tennis ball machine
A tennis ball machine has a spinning wheel inside. A slow ball rolls in, the wheel grabs it, and — whoosh — it shoots out fast.
The ball came in slow and left fast. Where did the extra speed come from? From the motor, through the spinning wheel. An does exactly this to water, non-stop.
- WatchStep 2 of 5
In the middle, out the edge
Water enters at the centre (the ), the curved grab it, and it leaves at the outer edge much faster.
Watch the colour: blue is slow water, orange is water that has picked up energy from the impeller.
Challenge: Set the speed to 0, then slowly raise it. Does the water come out faster when the impeller spins faster?
- ExplainedStep 3 of 5
An impeller in one sentence
An impeller is a spinning wheel with vanes that gives energy to a fluid. A motor turns a , the shaft turns the impeller, and the impeller pushes the fluid.
It never “sucks” or “squeezes” the water like a syringe. It flings it, using the effect you met in Module 1.
- ExplainedStep 4 of 5
Speed now, pressure later
Water leaving the impeller is fast. But in a pipe we usually need pressure — the push that lifts water to your shower on the third floor.
So every impeller lives inside a that catches the fast water and slows it down. Remember : when water slows down, its pressure rises. Impeller + casing together make a .
- The impeller connectionStep 5 of 5
You own several already
Your washing machine empties with one. Your dishwasher sprays with one. Your car engine is cooled by one, and the air in your vacuum cleaner is moved by one.
Here is a typical pump impeller. Drag it to look at it from every side — in the next lesson you will name every part.
📌 Remember this
An impeller is a spinning wheel with vanes. It takes fluid in at the centre and flings it out at the edge with more energy. Its casing then turns that speed into pressure.