Who is "they"? Do not raise your pH, foolishpleasure. If you search this forum, you'll see plenty of info about pH. Also, inexpensive pH meters are notoriously inaccurate, so unless you've purchased an exensive, high-quality pH meter, I would not trust the result. Citrus are pretty tolerant of a relatively wide pH range, with the ideal pH being between 5.5 and 6.5. 7.5 is getting on the outer edge of the pH range, but citrus will still do just fine at that pH, we have thousands of acres of commercial citrus groves here in the state of California that are in that pH range, and do just fine with no pH adjusting. Are you talking about potting soil, in-ground pH? If you make your own potting mix using the 511 mix, the pH should be fine.

As to your tap water, just check your municipal water district and look at your annual water report. Making a broad statement, "tap water is very alkaline" is not necessarily correct. All public water municipalities must by law disclose the pH of your tap water, so no testing needed, it is there for you in the annual report. The FDA requires public water to be within a certain pH range. Some municipalities do choose to keep their public water a little on the alkaline side for various reasons, but I wouldn't go so far as to say all tap water is "very alkaline", it can vary, depending on where you live in the country. In general (and this is a very generalized statement), tap water tends to be more acidic on the east coast, and more alkaline towards the west coast. You can acidify the water if you feel it is necessary, and 1 tbp of vinegar is plenty in a gallon. But, most folks find that is not necessary. I don't adjust my tap water at all for my potted citrus, my tap water is probably about that pH, and even a bit higher, and my potted citrus are all just fine.

Patty S.