Water is considered hard when it exceeds 3 grains per gallon gpg. A gpg is equivalent to 17.1 ppm. If you want to convert hardness in gpg to parts per million ppm you would multiply the hardness number by 17. So what will you notice at different hardness levels? 0–.5 gpg: Your water has been softened already 1-3.5 gpg: Your water doesn’t require softening because it is coming from a soft water source like surface water from a lake or river. You will get minimal or no scale buildup or staining. 3.5–7 gpg: Water between 3–7 gpg is moderately hard, causing spotty dishes and dry skin. At this level having a water softener is optional but if you have had one in the past and are particular about the cleanliness if you home you will want one again. 7–10.5 gpg: Hard water is packed with minerals at this level, and you likely deal with crusty stained faucets & pipes and possibly reddish rings on your porcelain from excess iron. You will not be able to use an on demand hot water heater or Ultraviolet Disinfection system without first softening the water. You will notice that you are getting scale buildup around faucets and fixtures, toilets will become stained. 10.5–14: Considered very hard, this water exhibits all the signs of hard water all the time. Glass shower doors and dishes will become very spotty. Whenever water sits anywhere in your home you will get a build up of lime scale and it will be difficult to scrub off. Your hot water heater will become less efficient due to the scale buildup and you will shorten the life of your dishwasher and washing machine. 14+: Extremely hard water is anything over 14 gpg. Glasses are extra spotty, skin feels super squeaky, dry and scaly. Soap scum will become an issue and there will be scale buildup everywhere. You will need to use far more soap to get clothes, dishes and people clean. If you’re on well water, you may also be seeing other problem water signs such as iron stains. If you try to wash floors with dark stain you will never be able to remove the streaks. It will cost you considerable amounts of money due to the damage caused by this extremely hard water if you do not get a water softener. Shop our Water Softeners here https://thewaterestore.com/collections/water-softeners-and-tannin-filters-the-water-filter-estore