Boiler Blowdown

Calculator and reference guide for boiler blowdown water quality requirements based on ASME guidelines. Calculates electrical conductivity from TDS and compares against maximum allowable impurities for different boiler pressure ranges. Includes water quality references and guidelines for maintaining proper dissolved solids levels to prevent scale formation, carryover, corrosion, and embrittlement.

Calculator

Inputs

Total Dissolved Solids (TDS) (ppm)

Conductivity Factor (μS/cm per ppm)

Results

Electrical Conductivity-- μS/cm

Boiler Pressure (psig)	Iron (ppm)	Copper (ppm)	Hardness CaCO₃ (ppm)	Silica (ppm)	Alkalinity CaCO₃ (ppm)	TDS (ppm)	Conductivity (μS/cm)
0 - 300	0.1	0.05	0.3	150	700	3500	7000
300 - 450	0.05	0.025	0.3	90	600	3000	6000
450 - 600	0.03	0.02	0.2	40	500	2500	5000
600 - 750	0.025	0.02	0.2	30	400	1000	4000
750 - 900	0.02	0.015	0.1	20	300	750	3000
900 - 1000	0.02	0.015	0.05	8	200	625	2000

Water Quality Reference Standards

Electrical Conductivity Ranges

Water Type	Conductivity (μS/cm)
Ultrapure water (20°C)	0.042
Deionized water	0.5 - 5
Soft ground water	100 - 300
Sea water	45,000 - 55,000
Concentrated acids/lyes	> 100,000

Key Blowdown Principles

Short, frequent blowdowns are more effective at removing boiler water sludge than infrequent long blowdowns
Manual blowdown required at boiler bottom to remove settled solids
Automatic continuous blowdown uses calibrated valve near water surface for predetermined rates
Blowdown tanks required by UPC/UMC codes for installations exceeding 15 psig
Recommended maximum TDS levels typically 2,000 - 10,000 ppm depending on boiler type

Problems from Inadequate Blowdown

Scale formation
Carryover
Corrosion
Embrittlement

Safety Warning: High pressure and temperature generate large amounts of flash steam during blowdown. Hot water and steam are dangerous—proper design, construction, and operational care required.