Tap water with campden or mineral water with gypsum?

[Weejock]

After reading some posts about hard water producing better beer than soft water, I used my aquarium test kit on my tap water to measure pH and dGH. Test kit shows pH of 8.4 and GH of over 16 degrees. In addition the Three Valleys website shows my postcode to have "very hard" water.

Any advice on whether I should continue using Asda mineral water or use my tap water with the addition of Campden?

[6470zzy]

I think that this would be an ideal situation to do a side by side brewing test. Why not split a batch with half being made with your tap water and half being the mineral water and then do a blind taste test with some of your mates? Believe me those blind taste tests are very informative.

Cheers