Recommended Feed Water Chemistry Limits
Steam boilers and ABMA recommended feed water chemistry limits
according to ABMA - American Boiler Manufacturers Association - are given in the table below:
| Boiler Operating Pressure (psig) (bar) | Total Dissolved Solids - TDS - (ppm) | Total Alkalinity (ppm) | Total Suspended Solids (ppm) |
| 0 - 50 0 - 3.5 | 2500 | 500 | |
| 50 - 300 3.5 - 20 | 3500 | 700 | 15 |
| 300 - 450 20 - 30 | 3000 | 600 | 10 |
| 450 - 600 30 - 40 | 2500 | 500 | 8 |
| 600 - 750 40 - 50 | 1000 | 200 | 3 |
| 750 - 900 50 - 60 | 750 | 150 | 2 |
| 900 - 1000 60 - 70 | 625 | 125 | 1 |
Maximum Allowable Impurities in Boiler Water
| Chemical | Symbol | Maximum Concentration (ppm) |
| Sodium sulphite | NA2SO3 | 1.0 |
| Sodium chloride | NaCl | 10.0 |
| Sodium phosphate | NA3PO4 | 25.0 |
| Sodium sulphate | NA2SO4 | 25.0 |
| Silica oxide | SiO2 | 0.20 |