Why boilers need to bleed
Every gallon of makeup water carries dissolved solids into a steam boiler. Steam leaves; the solids stay. Left alone, they concentrate until they foam, carry over into steam lines, and bake onto tubes as scale. Blowdown is the controlled removal of that concentrated water — the boiler's kidneys.
Two kinds, two jobs
- — Bottom blowdown: a short, sharp discharge from the mud drum or bottom of the shell that removes settled sludge. Done manually, typically daily on steam boilers.
- — Surface (continuous) blowdown: skims water from the surface where dissolved solids concentrate, controlled by conductivity. This is what holds your TDS at the target number.
The efficiency angle
Blowdown is hot water you paid to heat going down the drain — necessary, but worth minimizing. Too little blowdown scales your tubes (1/16" of scale can add several percent to fuel cost); too much wastes fuel and treatment chemicals. Automatic blowdown controls and heat recovery on the blowdown line usually pay for themselves quickly.
If your gauge glass looks like a snow globe or your steam traps keep failing on carryover, your blowdown program needs attention. Servco services blowdown systems and can pair you with the right water treatment approach for Intermountain West water.
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Quick answers
How often should bottom blowdown be done?+
Typically once per shift or daily on steam boilers, per the boiler manufacturer and your water treatment program. Your treatment vendor's TDS targets set the schedule.
Can blowdown heat be recovered?+
Yes — blowdown heat recovery preheats makeup water and is one of the fastest-payback upgrades on boilers with meaningful blowdown rates.
What happens with no blowdown at all?+
Foaming, priming, carryover into steam lines, scaled tubes, failed traps, and eventually tube failure. It's the cheapest thing you can do to extend boiler life.