Ive talked to many people about this same thing also. My tapwater was coming out about 8.3ish. It took a lot of ph down to get it around 6.5ish. I was having a lot of ph issues while doing this. I then got on ebay and ordered a small RO system for around 160. To make a long story short, i tested the same water out of the RO system and the ph read around 7. Rusty told me that the RO doesnt affect ph (i have yet to look this up because I trust the source). So either something in my tap water was either affecting my 2 ph pens(incorrect readings) or the ph down i was using. Either way, whatever the RO was filtering out has made all the difference in my grows. Now i just prefill my gallon jugs and when its time to water i just add a little molasses and water. Happy little plants now. Just something you might wanna check out.