Mechanical pumps and rain water isn't considered as water in ore washer.

Supplying ore-washer with rain from rain water barrels or by using copper create fluid pipes give the water without "H2O" tag.

Other option is flowing river water, the boiler do accept it and works fine

Ore washer will not work with regular not gregtech water

We are not Gregtech!!! I am not Greg.

In case anyone else finds this issue, this is the correct place to go:
TerraFirmaGreg-Team/Modpack-Modern#1797

Thank you for even answering, i was given this link on a server and didn't check from which mod it was.
I'm really sorry

can i delete it to not clutter the issues?