Water below 60 mg/L of dissolved calcium and magnesium (about 0 to 3.5 grains per gallon) is classified as soft. Whether that’s “too soft” depends on what’s happening in your home: slippery-feeling skin after washing, a flat or slightly metallic taste, or blue-green stains around copper fixtures are all signs your water may be softer than ideal. Naturally soft water and artificially softened water can both cause issues, but the problems and solutions differ.
How Water Hardness Is Measured
Water hardness is reported in either milligrams per liter (mg/L) of calcium carbonate or grains per gallon (GPG). The standard scale, used by most labs and water utilities, breaks down like this:
- Soft: 0–60 mg/L (0–3.5 GPG)
- Moderately hard: 61–120 mg/L (3.6–7.0 GPG)
- Hard: 121–300 mg/L (7.1–17.5 GPG)
- Very hard: over 300 mg/L (over 17.5 GPG)
If your water falls in the soft range, it contains very little dissolved calcium and magnesium. That’s great for keeping soap scum off your shower doors, but it can create other problems worth knowing about.
Signs Your Water Is Too Soft
The most obvious clue is how soap behaves. Very soft water makes soap extremely hard to rinse off. You’ll feel a slippery, almost slimy film on your skin and hands even after thorough rinsing. Shampoo lathers excessively, and you may notice your hair feels limp or greasy despite washing it well. Dishes and glasses can develop a filmy residue not from mineral deposits (that’s a hard water problem) but from soap that won’t fully rinse away.
Taste is another giveaway. Very soft water often tastes flat or slightly metallic, especially if it’s also acidic. That metallic flavor can come from trace amounts of copper or lead dissolving from your plumbing, which is one of the more serious concerns with excessively soft water.
Soft Water and Your Plumbing
This is where “too soft” becomes more than an annoyance. Soft water, particularly when it’s also low in pH, is more corrosive to metal pipes. Without dissolved minerals to form a protective scale inside pipes, the water slowly eats away at copper, brass, and lead solder joints. The Minnesota Department of Health notes that softened water can corrode pipes, and that corroded metal can end up in your drinking water, contributing to elevated lead and copper levels.
The mechanism is straightforward: harder water deposits a thin layer of minerals on the inside of pipes, which acts like a coating. Soft water never builds that coating, leaving bare metal exposed. In homes with older plumbing that contains lead solder or lead service lines, this is especially risky. Where dissimilar metals connect (lead pipe joined to copper or brass, for example), the softer, more reactive metal corrodes preferentially. Research on these galvanic corrosion cells shows that local pH at the joint can drop dramatically, accelerating lead dissolution into the water.
If you notice blue-green stains in sinks or tubs, that’s copper leaching from your pipes. Pinhole leaks in copper plumbing are another red flag. Both suggest your water is aggressive enough to damage metal over time.
The Sodium Question
If your water is soft because of a home water softener, there’s an additional factor: sodium. Ion-exchange softeners swap calcium and magnesium for sodium. The Water Quality Association estimates that every grain of hardness removed adds about 30 mg of sodium per gallon of water. So if your incoming water is 15 grains hard, a softened 8-ounce glass contains roughly 28 mg of sodium.
For most people, that’s negligible. The Mayo Clinic has noted that an 8-ounce glass of water softened from about 7 grains of hardness contains less than 12.5 mg of sodium, well within the FDA’s “very low sodium” definition. But if you’re on a sodium-restricted diet and drinking several glasses a day from water softened at high hardness levels, it adds up. In those cases, running a separate line of unsoftened water to your kitchen tap is a simple fix.
Missing Minerals and Health
Calcium and magnesium in drinking water contribute a small but potentially meaningful portion of your daily mineral intake. A large population-based study found that women drinking water high in calcium and magnesium had a 13% lower risk of ischemic stroke and a 22% lower risk of hemorrhagic stroke compared to those drinking mineral-poor water. Magnesium appeared to drive most of the benefit: the highest intake of drinking water magnesium was associated with a 31% lower risk of ischemic stroke. Magnesium has vasodilatory and anti-inflammatory properties and has been shown in clinical trials to lower blood pressure.
That said, the World Health Organization has not set minimum or maximum guidelines for mineral content in drinking water. The WHO acknowledges the epidemiological evidence for a protective cardiovascular effect but considers it insufficient to establish firm targets, since total mineral intake depends heavily on diet. If your water is very soft, you’re not in danger from the water itself, but you may be missing a small dietary bonus that harder water provides for free.
Skin and Hair Effects
People with eczema or sensitive skin often assume softer water will help, and there’s some logic to that. A meta-analysis of nearly 386,000 participants found that children living in hard water areas had 28% higher odds of developing eczema compared to those in softer water areas. But here’s the catch: two randomized controlled trials that actually installed water softeners in homes of people with established eczema found no significant improvement in disease severity. Hard water may play a role in triggering eczema, but once you have it, switching to soft water doesn’t reliably fix it.
For people without skin conditions, very soft water’s main effect on skin is that slippery, hard-to-rinse feeling. Some people find their skin feels drier afterward, possibly because the soap residue disrupts the skin’s natural oils. Using less soap is the simplest adjustment.
Impact on Water Heaters
Soft water is generally easier on water heaters than hard water because it doesn’t build up the thick mineral scale that reduces heating efficiency and shortens tank life. However, very soft water can accelerate the breakdown of sacrificial anode rods, the metal rods inside tank water heaters designed to corrode instead of the tank itself. If you have a softener, checking your anode rod every year or two and upgrading to a higher-quality rod (powered anode rods, for example) helps protect the tank without giving up the scale-prevention benefits.
How to Test Your Water
Home test strips are the fastest option. You dip a strip in a water sample and compare the color change to a chart. They’re inexpensive and reasonably accurate for identifying whether you’re in the soft, moderate, or hard range. For more precise numbers, especially at the low end of the scale where the difference between 20 mg/L and 50 mg/L matters, send-away lab kits provide detailed results including pH, total dissolved solids, and specific mineral concentrations. If you’re trying to determine whether your water is corroding your pipes, pH is just as important as hardness, so look for a test that measures both.
What to Do About Excessively Soft Water
If your water is naturally soft and you’re concerned about pipe corrosion, a calcite filter is the most common solution. These filters contain naturally occurring calcium carbonate that slowly dissolves into acidic or mineral-poor water, raising both the pH and the mineral content. They’re installed as whole-house systems or as point-of-use cartridges. The calcite gradually neutralizes aggressive water, reducing the risk of copper and lead leaching from your plumbing. The media needs periodic replacement as it dissolves, but maintenance is minimal.
If your water is soft because of a home softener, the fix might be as simple as adjusting the softener’s settings. Many softeners can be dialed back so they don’t remove every last grain of hardness. Targeting a finished hardness of 3 to 5 GPG rather than zero gives you the anti-scale benefits while keeping the water less corrosive. You can also bypass the softener for cold water lines that feed your kitchen, so your drinking and cooking water retains its natural minerals while your hot water system and bathrooms get the softened supply.
For homes with older plumbing, especially pre-1986 construction that may contain lead solder, testing for lead and copper at the tap is worth doing regardless of your water’s hardness. Even moderately soft water in combination with low pH can create conditions where metals leach into your drinking supply.