That sucks. I have to buy RO water for my reef tank so i fill 8, 5 gallon water bottles. They have water stores everywhere in my area. I used to get water delivered but it was too expensive now i just fill them myself. You should leave out you tap water for a day anyway, let all the chlorine and metals disipate. pH is very important for marijuana plants, so be careful if using tap water. For me it is so much easier and takes all the guess work out of watering (except how much) imo if you can use RO water it will make a big difference, and your buds will thank you.