If your tap water has a pH of 10, it’s not safe to drink! Rainwater will never have a ph of 10, nor should distilled water. I would suspect that whatever device you’re measuring with is not calibrated correctly. Most household products vinegar, citric acid, etc. are not very stable. I would suggest a product that is made to reduce PH.
Edit: But first verify those PH numbers, even cheap paper test strip can be used. A PH of 10 is the same as soda ash, and milk of Magnesia!