Factorio Forums

Although pollution amount is tiny, I still can see it on the map.

STR:
1. Choose a map chunk with no pollution (no red overlay)
2. Place a Small Pump
3. Connect it to electricity; don't connect it to any pipes
4. Map chunk is now slightly red

That's by design, the pump is still on and draining power from the electric network and as such it produces pollution.

If you disconnect the power from the pump you'll notice it stops producing pollution.