For plants, pH can mean the difference between thriving and languishing. There's a reason that specific plant types grow much better in certain areas of the world than others. Climate has a big impact, of course, but pH levels of soil and water is another large factor.
Most plants thrive at a pH around 6.1, give or take a few decimals depending on the plant. However when you water your plants with a garden hose or sink water, you are typically watering them with a pH over 7.5. This will not hurt the plants but only allow them to tinker along at an acceptable growth rate. While its better to have a slightly higher than lower pH from its optimal level, you still want to get your pH as close to the optimal level as possible. Here is a pH guide to the optimal pH of different plants.
How do you test pH? I use an electronic pH meter that you can buy on Amazon for less than $15 and it has been well worth it. I also purchased one that you can test the soil pH which is useful if you have high salinity soil, ie. Mexico, California, or anywhere near the ocean.
How do you reduce the pH of water? There are liquid based products that help reduce the pH of water but most of those are a quick fix, meaning they reduce the pH for a small amount of time and then the pH goes right back up so in the long run there is no real benefit. You want to use a "buffered" solution like Gorton's Ionized Solution. These types of solutions hold the pH at a selected level for a very long time.
How do you reduce the pH of soil? Most soil contain nutrients, salts, and other elements that attribute to a soil pH around 8.0. To reduce the soil pH you want to use water that has the optimal pH your are striving for. Over time the soil pH will decrease to where your water, soil, and runoff water all have the same pH level.
Commercial farmers and cannabis cultivators are keen to the pH of their water and soil as it has the potential to make them best in class. pH is an easy way that home gardeners can improve their gardens and make it look like you're a Master Gardener.