Operation & Optimization5 / 10
Boiler Blowdown & Water Treatment
Why blowdown happens, its energy cost, and how to minimise it.
9 min read · Jacob Willis, Net Zero Lead · Last reviewed July 2026
Blowdown is purposely draining hot water from the boiler to remove dissolved minerals before they form scale. If you don't blow down, the boiler gets encrusted with hard scale that insulates the water from heat and reduces efficiency. But blowdown has a real energy cost, and many boilers blow down far more than necessary.
In this lesson
- 01Why minerals accumulate
- 02How blowdown works
- 03The energy cost of blowdown
- 04How much blowdown do you actually need?
- 05Better strategies than continuous blowdown
- 06Practical action
- 07Sources and further reading