I'm not sure my save file is corrupt or something but I can't find the basic water filter. The advanced (+) version is available at Fiona but not the basic. Any tips where to find it? Thank you!

Edit: the walkthrough does not mentioning this item.

Anyone?

I can't believe nobody knows how to get it...

Haha I know, Just go towards west of West district You will find an alley connected to the police building....Towards left of the alley you will find the the way (stairs)
Make sure to bring a fishing rod , you will need that later.

Oh my god! Thank you!

hit the angle just right on sparkle in the hydro plant to fish it up (must have fishing rod crafted in inventory) north of the blue print