Boiler Makeup Water

Softening removes hardness minerals but leaves dissolved solids like sodium, bicarbonates, and silica in the water. At boiler operating temperatures above 200 degrees F, these residuals concentrate rapidly and cause carryover, foaming, and silica scaling on turbine blades. AMPAC USA recommends RO as the primary treatment stage, reducing TDS by 95-99% before water enters the boiler system.

ASME guidelines for boilers operating above 600 psi specify feedwater TDS below 0.1 ppm, which requires RO followed by mixed-bed deionization. For low-pressure boilers under 150 psi, many operators target feedwater TDS under 50 ppm. Our systems are sized to hit these targets based on your specific boiler rating and duty cycle.

Silica forms an extremely dense, glass-like scale on heat transfer surfaces that has roughly 10 times the insulating effect of calcium carbonate scale. Even a 1/8-inch silica deposit can increase fuel consumption by 25% and create hot spots that crack boiler tubes. RO membranes reject silica at 85-95% depending on pH, and a downstream polisher brings it to near-zero.

We size to peak demand plus a 20-25% buffer, then use a product storage tank to handle swing loads without oversizing the membrane array. A 10,000 GPD boiler makeup system with a 5,000-gallon storage tank can satisfy peak draws of 20,000 GPD for short periods. Variable-frequency drives on the high-pressure pump reduce energy consumption during low-demand periods.

At minimum, a 5-micron sediment filter and carbon block to protect membranes from chlorine degradation are required. Hard water above 7 grains per gallon benefits from a softener ahead of the RO to extend membrane service life. If your source water contains iron above 0.1 ppm, an oxidizing filter or iron removal step is necessary before the softener stage.