Every boiler accumulates dissolved solids. The feedwater entering the boiler contains dissolved minerals — calcium, magnesium, silica, sodium, chloride, and others — that do not follow the steam into the distribution system. They stay in the boiler water and concentrate as more water evaporates. Left unmanaged, this concentration increase causes two distinct problems: scale on heat transfer surfaces and steam contamination through carryover. Blowdown — the controlled discharge of concentrated boiler water — is the primary tool for managing dissolved solids concentration. Getting the blowdown rate right is not a minor operational detail. Getting it wrong in either direction carries real costs that compound over time.
What Happens When Blowdown Is Too Infrequent
When dissolved solids are allowed to concentrate beyond the recommended limits for the boiler operating pressure and design, two consequences develop in parallel.
The first is scale formation. Calcium carbonate, calcium sulphate, and silica deposits form on boiler tube surfaces when their concentration in the boiler water exceeds saturation levels. Scale has very low thermal conductivity — significantly lower than the steel tube it coats — and even a thin scale layer creates a significant insulating barrier between the combustion gases and the water. The boiler must fire harder and longer to achieve the same steam output, increasing fuel consumption. In the worst cases, scale buildup causes tube overheating, tube failure, and unplanned shutdowns.
The second is carryover. At high dissolved solids concentrations, the boiler water becomes more viscous and has a higher tendency to foam at the water surface. Steam generated at the surface carries water droplets — and the dissolved solids they contain — into the steam distribution system. This wet, contaminated steam deposits solids on steam trap internals, control valves, and heat exchanger surfaces downstream. In process applications where steam contacts the product — food processing, pharmaceutical manufacturing, laboratory sterilisation — carryover is a product quality and regulatory compliance issue, not just an equipment maintenance problem.
What Happens When Blowdown Is Too Frequent
Over-blowdown is the more common problem in facilities where blowdown is managed on a conservative fixed schedule rather than in response to actual measured dissolved solids. When the boiler discharges more concentrated water than the chemistry actually requires, three costs accumulate simultaneously.
Energy is wasted. Blowdown water leaves at boiler temperature and pressure. The thermal energy contained in that water is discharged to drain — heat that was transferred to the water from combustion and that is now lost rather than recovered as useful steam or condensate. In large boilers or high-pressure systems, this energy loss is substantial.
Make-up water consumption increases. Every litre of blowdown must be replaced with cold feedwater that must then be heated to boiler temperature. In facilities with water treatment costs, water purchase costs, or water discharge costs, unnecessary blowdown inflates all three.
Chemical consumption increases. Treatment chemicals — oxygen scavengers, scale inhibitors, pH conditioners — are dosed into the feedwater and are present in the boiler water. When water is discharged through blowdown, the chemicals go with it. Over-blowdown means over-consumption of treatment chemicals, reducing the cost effectiveness of the treatment programme and requiring more frequent chemical top-up.
What Dissolved Solids Measurement Provides
The correct blowdown rate for any given boiler at any given time is not a fixed number. It is the rate needed to maintain dissolved solids within the acceptable range for the boiler design and operating pressure — no more, no less. This range changes with feedwater quality variations, steam demand changes, and condensate return rate fluctuations. A fixed-schedule blowdown programme cannot track these variations. Only continuous dissolved solids monitoring can.
Conductivity measurement is the standard proxy for total dissolved solids in boiler water. As dissolved solids concentrate, conductivity rises proportionally. A continuous conductivity sensor in the boiler water provides a real-time TDS signal that allows blowdown to be triggered when conductivity exceeds a setpoint and stopped when it returns within range.
Lecol boiler water monitoring equipment provides the sampling and measurement infrastructure for continuous conductivity monitoring in steam generating systems, with appropriate pressure reduction and cooling to allow accurate measurement of high-temperature, high-pressure boiler water. The Aquarius controller integrates this conductivity signal with blowdown valve control, automating the blowdown cycle to maintain TDS within the defined range without operator intervention.
For boiler water dissolved oxygen and sulphite monitoring — which together complete the corrosion control picture alongside TDS management — the Pyxis inline sensor range provides continuous measurement of both parameters, flagging deaerator performance problems and oxygen scavenger residual depletion in real time.
For industrial and commercial boiler operators in Malaysia looking to reduce fuel, water, and chemical costs while maintaining steam quality and boiler integrity, automated TDS-based blowdown control is the most direct operational improvement available. To discuss system configuration for your boiler, contact us at info@autoflotechnology.com.