Tank and tap PH way off afraid to do a water change.

[mataichi]

I just got home from spending three weeks with family and tested my water before doing water changes. The PH in my 10 gallon tank was 6.6 but my tap water is all the way up to 8.4. Ammonia 0ppm Nitrite 0ppm but my nitrate is 100+ so I need to do some water changes but I'm afraid to use my tap water right now. I topped up the tank with one gallon and the ph went from 6.6 to 7.2. Should I go buy some water? I have a gold fish tank that's not as far off Ammonia 0ppm Nitrite 0ppm and Nitrate 40ppm. I think I will do a 4 gallon water change in there but I'm really worried about my 10 gallon tank. I want to bring the nitrate down but I don't want to raise the ph any more then I already have.