Type your town into the full water report on the homepage for the complete readout. The table below is the hardness cut from that same 2026 file - grains per gallon, the number that spots glasses and kills water heaters.
| Town | Grains / gal | How hard |
|---|---|---|
| O'Fallon | 8.0 | Hard |
| St. Charles | 8.9 | Hard |
| St. Peters | 9.0 | Hard |
| Dardenne Prairie | 10.0 | Very hard |
| Foristell | 10.7 | Very hard |
| Lake St. Louis | 10.8 | Very hard |
| Wright City | 10.8 | Very hard |
| Wentzville | 14.0 | Very hard |
| Warrenton | 16.0 | Extremely hard |
| Washington | 16.5 | Extremely hard |
| Troy | 19.2 | Extremely hard |
Anything over 7 grains is hard. Over 10.5 is very hard. City water and a private well on the same street can read different - that is why we still come out and test your tap, free.
See the map of the same data: water quality map.
Book the free in-home test
An owner tests hardness, iron and chlorine at your sink and tells you straight.
Or call (636) 899-1040.