Choosing source of Water
Pure H2O is 0 parts per million (PPM), but your tap water has other chemicals in it. You have 3 main types of water.
You’ll see a lot of debate over this, but I think tap water is completely fine to use as long as the ppm isn’t outrageous. In my opinion, if your tap water ppm is over 300 you might run into some issues, especially when you’re in the seedling stage. My tap water has always been under 250 ppm and it’s usually easily under 200 ppm and I never had an issue. When watering with tap just make sure to let the water sit out for a couple days, so the chlorine can evaporate off. Don’t boil your water to evaporate the chlorine, because while it works, you also lose water while retaining all the salt.
I would personally just avoid buying this as the ppm vary from brand and it will get stupid expensive fast.
RO (reverse osmosis) water is what most professionals use and it’s created by running water through a reverse osmosis device (Not to be confused with the filters that fit your drinking facet). This water is completely pure and will have a ppm of 0 or damn close to it. Distilled water is just another term for it and you see it sold in grocery stores. RO filtration systems are quite expensive, with basic ones starting around $100 and good ones around $200. Though that is a whole lot cheaper in the long one compared to buying distilled water. This is the best water hands down to use, but most beginners that want to save money should try/test their tap water first.