Boiler Blowdown Calculator
Boiler Blowdown Calculator: Control Dissolved Solids Buildup
Boiler blowdown is the deliberate removal of a portion of boiler water to control the concentration of dissolved solids (TDS) that build up as steam is continuously generated and pure water leaves the system. Without blowdown, TDS levels climb until they cause scale formation, foaming, and carryover into the steam lines. This calculator tells you exactly what percentage of your feedwater rate must be blown down to keep TDS below a safe operating limit.
The Formula
Blowdown % = Feedwater TDS / (Max Boiler Water TDS − Feedwater TDS) × 100
Worked Example
A boiler is fed with water containing 5 ppm TDS, and the maximum allowable boiler water TDS is 55 ppm.
Blowdown % = 5 / (55 − 5) × 100 = 10%
This means 10% of the feedwater rate must be continuously blown down to hold the boiler water at or below 55 ppm TDS.
How to Use This Calculator
- Enter the feedwater TDS in ppm, as measured from your water treatment system or lab report.
- Enter the maximum boiler water TDS allowed for your boiler's pressure class (check manufacturer or ABMA guidelines).
- Click Calculate to get the required blowdown percentage.
Related Calculations
Pair this with the Boiler Fuel Requirement Calculator and Steam Boiler Efficiency Calculator to get a full picture of boiler operating costs.