I went to the hardware shop, and it was the most "pure" thing they had.
Is it ok to go?

What is it for? I use tap water for plant extractions with no issues.

Cyb's salt tek.
Tap water has pollutants that may affect the yield.

Wich ones and how do they affect yield?

I've used tap water and saw no difference in that TEK (even for the freeze step for which I used to use distilled water because I thought it would help with osmotic pressure and cell bursting, but there was no difference in practice).

No idea.
But I wouldn't trust my city's water to to drink, let alone working with it .

The water in my area is treated with Chlormonium. It clouds up glass, leaves sediment in boiling pots and destroys plumbing. I haven't tried to use it to extract and don't think I will either. It causes mold issues in mush cult so I use distilled water to hydrate and rinse grains. The only thing I use it for is washing jars and I dry them thouroughly before extraction to remove any residual chlorine or ammonia.