Build a DIY pump
Motor, casing, seal and your printed impeller: put together a small pump that really works.
⏱ 8 min
- Everyday comparisonStep 1 of 6
A kit of parts
A bicycle is just a frame, wheels, pedals and a chain — but only when they are put together correctly does it ride.
A pump is the same: impeller, casing, motor and seal. Each one has a simple job, and you already know them all.
- ExplainedStep 2 of 6
Safety first
Use only a low-voltage (6–12 V) with a battery or a proper plug-in power supply. Never use mains electricity near water.
Keep the motor above the water and dry. Wear safety glasses when anything is spinning, keep fingers away from the impeller, and ask an adult to help if you are young.
- ExplainedStep 3 of 6
What you need
Your printed impeller. A small DC motor, for example a 12 V hobby motor of the “775” size. A casing: print the matching volute casing from the Impeller Designer (body + cover), or use a sturdy plastic food container with a hole in the lid for the inlet and one on the side for the outlet.
A seal where the shaft enters the casing: a small or a snug . Tube for the outlet, silicone or screws to close the casing, and a 12 V supply.
- WatchStep 4 of 6
Where the parts go
Water enters at the centre, over the eye. The outlet leaves the casing tangentially — along the edge, in the direction the impeller spins — just like the volute here.
- ExplainedStep 5 of 6
Putting it together
1. Fix the impeller on the motor shaft (tight press-fit, a drop of glue, or a small set screw). 2. Mount the motor on the back of the casing with the shaft through the seal.
3. Close the casing. For a semi-open impeller, keep the gap between the vane tops and the cover small — about 1 mm — or water just slips over the vanes. 4. Put the outlet tube on.
5. Submerge the inlet in a tub of water (the pump must be full — remember ), switch on, and check it spins in the right direction: the vanes’ tips should trail behind.
- The impeller connectionStep 6 of 6
If it doesn’t pump
Use the pump doctor’s checklist from Module 6: Is it primed? Is air leaking in? Is it spinning the wrong way? Is the gap over the vanes too big? Fix one thing at a time.
Every engineer’s first has problems. Finding them is the fun part.
📌 Remember this
A DIY pump needs your impeller, a low-voltage DC motor, a casing with a central inlet and a tangential outlet, and a shaft seal. Keep the gap over a semi-open impeller small, prime it, and check the rotation.