Why You Might Still See Watermarks — Even with a Water Softener!
It can be confusing to notice watermarks after you’ve had your water softener installed, especially when softened water is meant to reduce marks and limescale. It would be entirely understandable for you to think your softener is not working. However, the truth is, there are a couple of other more likely possible reasons — and neither means your softener isn’t doing its job.
Hard Water Protective Coatings
Every so often, we come across bathroom fittings that have been factory-treated with what’s known as a hard water coating. These coatings are designed to make taps, showers, and basins more resistant to limescale — but once you introduce softened water, they can sometimes behave in unexpected and unwanted ways.
When softened water meets certain coatings, it can bead or sit on the surface rather than rinsing cleanly away. As the water evaporates, a faint watermark may appear — not from limescale, but from how the softened water interacts with the coating.
It’s fairly rare to see this; in fact, we see only two or three such instances a year. But it does happen.
Usually, it affects just one or two fittings in a home — often higher-end or designer brands. If you’re planning a bathroom refurbishment, it’s well worth checking whether your chosen taps or shower heads, including shower cubicle or bath shower glass, have a hard water coating before you buy.
If you notice watermarks appearing, check the manufacturer’s specifications. Where coatings are present, simply wiping down surfaces after use will prevent any visible marks forming.
As a general guide, the biggest brand we find this problem with is Grohe fittings (sold through Graham's merchants) - these tend to have hard water coatings, whereas Iflo or Bristan (from City Plumbing and others) generally do not. Of course, there are plenty of exceptions — so a quick bit of research before purchasing is always time well spent.
Naturally Occurring Minerals in the Water
It’s also important to remember that a water softener doesn’t remove every mineral — only calcium and magnesium, which are responsible for limescale. Other trace minerals remain present in the supply, including small amounts of copper, chromium, potassium, phosphorus, sulfate, fluoride, radium, nitrate, and others.
These minerals are completely normal and typically harmless, but on rare occasions, they can leave faint deposits or marks when water droplets dry on glass, chrome, or ceramic surfaces.
If you’ve ever noticed how professional window cleaners achieve a flawless, streak-free finish, it’s because they go far beyond softening. They often purify their water in three stages — first through a softener, then a reverse osmosis system, and finally through DI (deionising) resin, which removes virtually all remaining minerals. That combination produces water that’s 99.9% pure — perfect for crystal-clear glass.
Of course, using such a system at home would be completely impractical, and quite aggressive to metals too, but it’s a useful comparison. It helps explain why, in very rare cases, a faint watermark might appear even when fittings aren’t coated and your softener is working perfectly.
In Summary
Softened water makes cleaning easier, protects appliances, and keeps your home sparkling — but on the rare occasion you spot a watermark, it’s nearly always down to a coating or a trace mineral rather than a fault with your system.
A quick wipe after use will usually solve it — and if you’re ever unsure, we’re always happy to guide you on how to check whether your fittings could be contributing to the problem.