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How to increase PH in closed circuit heating systems ?

Roohollah Member Posts: 135
Dear Professionals ,

To begin with , I would like to sincerely appreciate for sharing your knowledge and experiences with us . This place comprises with academic and practical atmospheres and great source of learning .

We have reinstalled a closed circuit boiler room which composes of two floor standing cast Iron boilers and SCh40 steel pipes and fittings .AS usual , we test the system's water to make sure that it is not acidic or corrosive . Yesterday, we did and we found that it was 6.4 . In this case, we took the partial system's water to add Sodium Carbonate to increase The PH and after dilution ,we pumped to the system again . We ran the system for two hours and again tested it . Fortunately , the system PH raised to 10 . Now, We are so interested to know whether Sodium carbonate is good choice for this application and what is the acceptable PH in closed circuit heating system ?

Thank you in advance for your support and time ,

I look forward to hearing from you ,

Yours Sincerely,



  • lchmb
    lchmb Member Posts: 2,997
    on the PH scale your looking for 7. I like to treat my new installs to a bottle or two of 8 way and then add PH plus or minus depending on the need..
  • hot_rod
    hot_rod Member Posts: 22,120
    It's good to know and check the ph. Do you also check conductivity? A basis TDS check is a good idea. The minerals in your water can coat out all the surfaces and put a hit on energy transfer both in the boilers and heat emitters.

    Chlorides are also a number to watch.

    Here is a good primer on fluid quality.


    I am a proponent of hydronic conditioners also. Good conditioners will buffer ph, scavenge remaining O2, add a micron layer of a film provider to protect new metals, and keep small solids in suspension. They should be added to good quality water if possible. You might find Fernox or Sentinal brand in you area, they are is a global providers of boiler cleaner and treatments.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • SWEI
    SWEI Member Posts: 7,356
    pH of 7.0 might be a bit on the low side for steel & iron.
  • Roohollah
    Roohollah Member Posts: 135
    Dear Friends,

    Thank you for the instructive inputs and taking the time to help us .

    As regards adding proper Hydronic conditioner , we have added specific hydronic conditioner which protects the metals and Alloys in the system without corrosion .The conditioner's company sent us a sample of this inhibitor in past in which there were two pieces of copper and metal in it . We checked it the sample after a year without any sign of corrosion over those metals . The color of this solution is black ,but when it mixes with water it turns to light purple .

    The project has been installed since last January . We usually check the circulators' housings and there has been a thin layer of the solution inside of circulator's housing ,and we have not seen any sign of scales or reddish water or oxidation over inside of system's fittings or circulators .

    We will measure TDS of the system . However, we do not know what is the properest scale of TDS of closed circuit heating system. We would like to request you professionals to inform us of it .

    Once more , we appreciate you all devoting your valuable time to support us to do the job rightly .

    I look forward to hearing more from you at your convenience time .

    Yours Sincerely,