One of the biggest problems with water-bath stand-by propane vaporizer systems is corrosion of the vaporizer heat exchanger and water box. Corrosion occurs when the water-bath heat transfer media fluids (a mixture of deionized water and ethylene glycol or propylene glycol) are installed without rust inhibitors.

Without the proper inhibitors in the (Glycol/DI Water) heat transfer fluid the carbon steel heat exchanger and water box of the propane water bath vaporizer will corrode and eventually fail. A failure of this nature will make the propane back-up system inoperable, causing expensive repairs and down time when the system is needed due to natural gas curtailment. The inhibitor also stabilizes the pH to maintain an environment for less corrosive conditions.

Heat transfer fluids should be checked every year prior to the winter season when natural gas curtailments most likely occur. It is also recommend that the heat transfer fluids be replace once every five years.

Depending on the glycol used this may require that the heat transfer fluids be disposed of by an authorized remediation vendor.

The mixture/ratio of glycol and DI water will depend on the freezing zone where utilized.

Why choose inhibited glycol?
When glycol is exposed to heat or oxygen, it can break down and cause damage to metals in the system. By using inhibited glycols, the system is buffered to protect against this damage and provide corrosion protection as well.

How do I know which glycol to use?
Ethylene glycol is normally used in most HVAC applications because it offer the most efficient heat exchange media. Propylene glycol is used where possible contact with potable water and food could occur.

Please note, deionized water is recommended to be used in lieu of ordinary city water for the mixture.

Below are visual examples of what the heat transfer media will look like after one year without rust inhibitors. 

The above is also recommended for industrial & commercial closed-loop water based HVAC Boiler systems.