What causes the spots
| Sign | Likely cause |
|---|---|
| Chalky white crust that dissolves in vinegar | Calcium hardness |
| Faint spots on glass after rinsing | Dissolved solids, including remaining hardness |
| Cloudy glassware that will not wipe clean | Detergent etching |
| Orange or brown marks | Iron, usually from an irrigation well |
A quick home check: wipe a spot with white vinegar. If it dissolves, it is mineral scale. If it does not, it may be etching, soap film, or something else that a softener will not fix.
What the utility removes, and what it leaves
Lime softening precipitates much of the calcium as sludge at the plant. WASD then adds a phosphorus compound for corrosion control. The water reaching Miami Shores is softer than raw Biscayne Aquifer water but not mineral-free. Whether what remains is enough to bother you depends on your tap reading and your tolerance for spots.
Softener, conditioner or RO
- Ion-exchange softener: removes remaining hardness throughout the house. Living Water's softeners work this way.
- Salt-free conditioner: does not remove hardness minerals; spots can still form where water dries.
- Under-sink RO: for spot-free drinking water, coffee makers and glass rinsing, without treating the whole house.
See salt-free conditioner vs. ion-exchange softener.
Many Miami Shores households find that an RO at the kitchen sink solves the spots they care most about, on glassware and in coffee and tea makers, without treating every tap. A whole-house softener makes more sense when scale shows up throughout the home and in the water heater.
Pools and outdoor surfaces
Pool owners see a white scale line at the waterline tile, especially when topping off often in dry months. Iron from irrigation wells causes a different, orange stain. See orange stains in Miami Shores.
Tankless water heaters deserve attention: their manufacturers often specify maximum hardness and recommend periodic descaling. Compare that specification with your tap reading.
Easy wins
- Squeegee shower glass after use.
- Use a dishwasher rinse aid.
- Soak aerators and shower heads in vinegar.
Does the Preston plant's water differ? WASD says Preston uses enhanced softening because its source water has more natural organic material.
Measure first
Call, text or WhatsApp Jorge at (305) 793-5974. If your hardness is low, Jorge will tell you a softener is not needed.
Updated 2026-10-17 · Living Waters · Jorge Canela, Water Quality Specialist