How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Rick Your Own Question
Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 21801
Experience:  40+ yrs. experience as a licensed oil & gas technician.
Type Your HVAC Question Here...
Rick is online now
A new question is answered every 9 seconds

Four years ago we had our plumber winterize our boiler by

Customer Question

Hello ------ Four years ago we had our plumber winterize our boiler by adding 10 gallons (100) of propylene glycol to the loop system. This year when I had my boiler serviced I asked the technician to check the level of freeze-protection which turned out to be +20 degrees. I asked him why the copper/brass pipes, circulator pump and shut-off valves are all covered in a powdery green patina. He said that he suspected the anti-freeze is having a corrosive effect on the system. Would like to add more anti-freeze in order to provide greater freeze-protection but am concerned about doing more damage to my heating system. Or, am I too late?
Would really appreciate any advice you can offer. I'm in a real quandry.
Thank You,
Submitted: 1 year ago.
Category: HVAC
Expert:  Rick replied 1 year ago.

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. If my initial response doesn’t answer your question then let me know and we can continue our conversation.

Glycol is not corrosive unless it's left in the system too long (typically over 6 years) without a corrosion inhibitor being added periodically. But unlike water which evaporates from minuscule leaks before it's noticed, glycol leaves a residue. That's likely what you're seeing and it's nothing to be concerned about. I've had glycol in my heating system for 30 years with no ill effects and yes I do have some of the same deposits you describe. One thing I would mention, unless to live in an area where is gets extremely cold a 60/40 (60% glycol) mix is perfectly adequate. I'm in NH and that what I have in my system.