Help with ph

So my tap water runs at about 7.5-8 and I was trying to get it about 5.7-5.9 my ph down says add 1-3 ml to 38 liters of water I added almost 10 ml and the ph was still at 7

Yeah, for my DWC reservoir I have to put quite a bit of PH down in my water to get it from 8 to 5.6. I don't think it's that unusual, all depends on where you live and what the town/city does to the water.

What PH down are you using?

Cheers
- SB -