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hard water in dishwasher

How to Test for Hard Water in Dishwashers

A frequent complaint with dishwashers is the appearance a filmy white substance on your dishes after you run a load. Many people mistake this for soap scum, but this is typically a sign of hard water in the dishwasher. The most obvious symptom of hard water is white spots or streaks on glassware, but you may also notice cloudy and dull silverware. To help you address this problem, we’ve created this guide to show you how to test for hard water in dishwashers and what to do about it.

What Is Hard Water?

The word “hard” in hard water refers to the mineral content of the water. All water contains trace minerals, many of which are healthy, but “hard water” is used to describe water that has particularly high levels of calcium and magnesium deposits due to percolating through limestone, chalk, and/or dolomite.

hard water in dishwashers

This calcium and magnesium can build up over time on any surfaces regularly exposed to water including dishes, sinks, faucets, or even the tray under your water dispenser. Hard water also inhibits the effectiveness of detergent. With soft water, soap will become much more active, producing suds quickly and easily.

Do I Have Hard Water?

To identify the issue as a hard water problem, there is a simple vinegar test that you can perform. Choose a glass that is particularly cloudy, spotty, or streaky. Get a paper towel or dry rag and moisten it using vinegar. Any type of vinegar will do, but distilled white vinegar is best. Now run the towel along both the interior and exterior of the glass. If the residue easily wipes away, this indicates that you have hard water.

How to Test for Hardwater in Dishwashers?

hard water test

If you’d like a more precise estimate of the hardness of your water, you can purchase a hard water test at most home repair stores. If you use the public water supply, you can request information about the level of water hardness in your area from the water department at your local town hall.

What Can I Do to Manage Hard Water in Dishwashers?

There are several ways to adjust to hard water levels in your home. To change the quality of all the water in your home, you can purchase a water-softening system. Typically, these systems replace calcium and magnesium with sodium.

Unfortunately, high sodium levels are not recommended for watering plants and may be unsuitable for drinking without filtration. Instead, you can try a magnetic water conditioner designed to alter the calcium ions to prevent limescale from building. Although cleaner and easier to use, the effectiveness of this method is somewhat debatable.

Water Softner


An easier option is simply to change the quality of the water directly in your dishwasher. This can be done using specialty dishwashing detergents or additives, like Finish, that are formulated specifically to work with hard water. These use a softening agent to eliminate limescale buildup. You may want to get a precise measurement of your water’s hardness before determining which hard water detergent/additive is right for you.

If you are having hard water problems in your dishwasher, it is guaranteed that the clothes washer is having the same problem. A tell-tale sign that the washing machine is suffering from hard water problems is slightly faded clothing with a scratchy texture.

We hope that this guide has given you a better understanding of hard water in dishwashers and how it affects your dishes. For all of your dishwasher maintenance and repair concerns, you can count on Cody’s Appliance Repair.

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