Chicago tap water comes from Lake Michigan and runs roughly 130 to 150 ppm hardness, about 7.6 to 8.8 grains per gallon, which sits in the “hard” band on the Water Quality Association scale. The cloudy film on shower glass is calcium and magnesium scale, not soap residue, which is why an all-purpose spray does nothing to it.
Is Chicago tap water hard?
Yes. Chicago draws essentially all of its drinking water from Lake Michigan, which picks up dissolved calcium and magnesium from the limestone and dolomite bedrock of the Great Lakes basin. Reported hardness sits around 130 to 150 parts per million, roughly 7.6 to 8.8 grains per gallon. On the Water Quality Association scale, hard begins at 7.0 grains per gallon and very hard at 10.5, so Chicago is solidly in the hard band without being extreme.
This is not a health issue. Hardness is a fixtures and appliances issue, and for our purposes, a cleaning one.
Why does shower glass go cloudy?
Every time water evaporates off glass, the dissolved minerals stay behind. One shower leaves a film too thin to notice. A year of showers leaves a bonded mineral layer, and because it forms in thin repeated deposits it is much harder to remove than a single thick spill would be.
Soap scum is a separate problem that often sits on top, formed when soap reacts with the same calcium. The two together are why a shower door can look permanently hazy despite being wiped weekly.
Why does regular cleaner not remove it?
Most all-purpose sprays are neutral or mildly alkaline, and they are formulated to lift grease and grime. Mineral scale is alkaline itself, so an alkaline cleaner has essentially no effect on it. Scale needs an acid to dissolve, and it needs time in contact with that acid.
This is the single most common reason people conclude their shower is "just old." It usually is not.
How do you remove hard water film?
- Use an acidic descaler. Products based on citric, lactic, or phosphoric acid are made for this. White vinegar works on light buildup.
- Let it sit. Five to ten minutes minimum. Spraying and immediately wiping accomplishes almost nothing, and this is where most attempts fail.
- Agitate with a non-scratch pad, then rinse fully and dry the glass rather than letting it air dry.
- Repeat on heavy buildup. Layers came on one at a time and often come off the same way.
One safety point that matters. Never mix an acidic descaler with bleach or any chlorine-based product. The combination releases chlorine gas. If you have used a bleach-based cleaner in the shower, rinse thoroughly before switching.
Also check what your glass actually is. Untreated glass that has been left for years can become physically etched, where minerals have pitted the surface. Etching is not a film and it cannot be cleaned off. If a proper acid treatment with adequate dwell time does not improve it, that is usually what you are looking at.
How do you keep it from coming back?
A squeegee after each shower is genuinely the most effective habit, because scale cannot form from water that is not there. Beyond that, a periodic acid treatment prevents the layers from bonding into something that needs a serious intervention. Households in Chicago with glass shower doors are also the ones most likely to eventually find a water softener worth the cost.
Does hard water affect anything else in the home?
Yes, and the same scale shows up in places people do not connect. Spotting on glassware out of the dishwasher, white crust around taps and shower heads, reduced flow from a shower head as the holes narrow, dulled tile, and scale inside kettles and water heaters. If your glasses come out of the dishwasher cloudy, that is the same mineral, not a dishwasher fault.
Hard-water removal on glass, fixtures and tile is part of our deep clean rather than a general clean, because it is dwell-time work rather than wiping.
Common questions
How hard is Chicago tap water?
About 130 to 150 ppm, or 7.6 to 8.8 grains per gallon, sourced from Lake Michigan. That is classed as hard, since the hard band begins at 7.0 grains per gallon.
Is hard water in Chicago dangerous?
No. Water hardness is not a health concern. It affects plumbing, appliances, soap performance and cleaning, not safety.
Can cloudy shower glass be fixed permanently?
Mineral film can be removed with an acidic descaler and enough dwell time. Glass that has been physically etched by years of untreated buildup cannot be restored by cleaning.