I just use tap water, as I really have no other option. I grow in pots, and my plants are typically very happy campers, which I attribute more to the fertlizer I use and my hauling them into the garage when the weather's nasty, rather than much of anything else. Frankly, I get the least-expensive potting soil I can find - I considered Scott's last year, but something else was less expensive. My bigger question about your buckets is whether you have sufficient drainage. Peppers like to be moist but not wet. If you don't have to water them at least once a week (and more frequently in the summer), then you don't have enough drainage. I used to live in Houston and still have fam there, so I am familiar with your growing conditions. Note also that with as hot as it gets there, sometimes the plants will drop their flowers because it is actually too hot for them. If you have a way to get them some shade in the heat of the day, I'd recommend that you do so.