Hard vs. Soft Water: 

While we may prefer soft water, our lawns don't. Lawns prefer hard water because it contains high levels of calcium and magnesium, which are two micronutrients required for plant growth. 

Soft water tends to contain more sodium than calcium and magnesium. Too much sodium can cause lawns to turn yellow and, in severe cases, harm soil structure or kill plants.You can occasionally water your lawn with collected rainwater to help dilute the soft water and avoid a sodium build up. Adding plenty of compost can also help avoid this by improving the soil's drainage capacity.

Wells vs. Municipal Water:

Well water is whatever Mother Nature decided to rain down. You can test the water to monitor mineral levels to alert you to any potential sodium or fluoride problems. 

Municipal water tends to contain chlorine and fluoride. While chlorine is needed to grow plants, there could be an overload. To combat that, fill a bucket with water and let it sit uncovered overnight. This will allow the chlorine to evaporate. The fluoride in municipal water poses a bigger threat. A build up of fluoride will build up in the tips of grass causing a phenomenon called necrosis. Necrosis causes the grass to turn yellow and burn. The best way to combat this is to add lime or wood ash to the soil to balance the pH.