Gusaroneanswered grow question 3 years ago Well you could test your water for dissolved solids, the ppm level. It's its low enough, then I'd say it's fine to use. Some people buy a reverse osmosis system to filter their water and that will take all the solids out. You could also look online for the breakdown of dissolved solids in your town water supply. Where I live it is about 120 ppm, which is on the lower end. I heard California water is 400, which would be considered high and probably better off if you filter it.