Johnston Boiler

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Johnston Boiler

Celebrating 150 years of innovation

Home > Resources > General > Water Quality

Water Quality

Recommended Water Quality For Firetube Boilers

Feed Water

pH8.5–9.2 – Should be alkaline at all times.
HardnessZero ppm
SilicaDictated by blowdown and maximum boiler residuals.
Total Dissolved Solids (TDS)Dictated by blowdown and maximum boiler residuals.
Dissolved OxygenShould be reduced to less than 0.005 cc/l by mechanical deaeration and the residual controlled by addition of a suitable oxygen scavenger – normally sodium sulfite.
Suspended MatterZero
Oil and GreaseZero

Boiler Water

pH10.5-11.5
Alkalinity (m)700 ppm (max.)
Total Dissolved Solids (TDS)Boilers sized 20,000 pph or less – 3500 ppm (max.). Boiler sized larger than 20,000 pph – 2500 ppm (max.)
Phosphate Residual50 ppm as PO4 (min.)
Dissolved OxygenZero. If sodium sulfite is used for oxygen scavenging, maintain 25-50 ppm as Na2SO3.
Suspended Matter50 ppm (max.)
Oil and Grease125 ppm (max.)

This information is supplied as general guidance only and does not absolve the boiler owner from the responsibility of determining and maintaining water standards appropriate to the specific local water chemistry and specific boiler use.

  • About
  • History
  • Vision & Mission
  • News & Events
  • Green Technologies
  • Why choose JBC?
  • Education & Training
  • Customer Installations
  • Photo Gallery
  • Factory Tour
  • Products
  • 509 Series Boiler
  • XID Scotch Marine Boiler
  • 358 Series Boiler – Ohio Special
  • 309 Series Boiler
  • WHR Series Boiler
  • Burners
  • Ancillary Equipment
  • Resources
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  • Johnston Boiler
  • 300 Pine Street
    P.O. Box 300
    Ferrysburg, MI 49409-0300
  • P (616) 842-5050
  • F (616) 842-1854
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