Collection: Pumps with a large free passage

What is free passage, and how much do you need?

The free passage is the largest solid particles a pump can handle unhindered. If the passage is too small for what is in the water, the pump clogs — often at exactly the moment you need it.

A rule of thumb

• Up to 10 mm: clean and lightly contaminated water, rainwater, cellar water.
• 20 to 30 mm: sludge, leaves, water containing sand, construction water.
• 40 to 50 mm: coarse waste water and applications where you never want anything to get stuck.

If you are torn between two sizes, take the larger one. A pump that clogs once a year costs you more in removing and cleaning than the price difference.

Do make sure the discharge pipe grows with it: a large passage is of little use if the pipe behind it is narrow. If it concerns waste water containing sewage, see sewage pumps; there a cutter pump is sometimes the better answer with a thin pipe.