Protecting your investment is crucial. First, glycol is not just for freeze protection. Chillers in the south can benefit from glycols, too. A 20% solution will keep the system clean and new and the heat exchangers at top efficiency.

The tendency is to buy the cheapest antifreeze that will do the job. Unfortunately, the cheap antifreezes will not do the job properly in a chiller system.  

RV Antifreeze is already 65% water when you buy it. It is also formulated to work in piping that is not circulating. It is made for winterizing plastic RV piping.  At full strength it will only protect you to about 10F. 

Automotive antifreeze is the next cheapest. It is made with silicones which are harmful to pump seals. It is also made for hot water systems, not cold water systems. Over time, the additives will turn to a jelly like substance and stick to the walls of the heat exchangers in the machinery and chiller. It is especially bad if you have hard water over 8 grains. 

The proper antifreeze to use is an inhibited HVAC glycol that is made for refrigeration systems.  

Inhibited glycol comes in two forms 

1. Ethylene glycol based, which is a hazardous waste according to the EPA. Most automotive antifreezes are ethylene glycol based. That is another reason not to use them. Otherwise, ethylene glycol based HVAC solutions are very good.  

2. Propylene glycol based antifreeze. This is next to food grade and will not harm the environment or animals or people if
    ingested.  We strongly recommend these glycols over all others.

Caution:  These two should never be mixed.

Inhibited glycols for HVAC systems is available from any good industrial chemical distributor like Ashland Chemical or Dow Chemical. We sell Dow Frost in 55 and 5 gallon containers.

Most refrigeration supply distributors also sell some form of HVAC glycol. United Refrigeration sells Freeze Kontrol by Nu Calgon. Virginia KMP also has a brand.  

Use of glycol in warm climates is strongly recommended. You may not be in danger of freezing but the additives in glycol will keep the heat exchangers clean and the piping lubricated. Scale and lime deposits are much less in a protected system. A minimum 20% solution should be used for this purpose. 

Protecting your Cooling Tower System

Glycols are only to be used in refrigeration systems.  You should not use glycols in Cooling tower systems as it will turn into a jelly like substance that will prevent the sprinkler arms from turning.

Most Cooling Tower Systems will have a storage tank located inside the building that the water will drain down into when the system is shut down. This should be enough to protect your system from freezing.