Replies

1. 
   TLRice | Mar 05, 2003 09:25pm | #1

   Glycol is commonly used in hydronic heating (i.e. forced hot water) systems where pipes or coils are potentially subject to freezing temperatures as an antifreeze. This is basically the same stuff that is in your car, but do't put Prestone in your heating system. The use of glycol changes the amount of heat each gallon of fluid can contain at a given temperature, and changes the operation of the system. Coils, radiators, finned-tube convectors and PEX tubes are all sized differently  when used with glycol.

   So what does that mean in English? It will make the heating system less effective (not less efficient) than if it had 100% water.

   Cons: None, really, except maybe cost and hassle, some reduction in system capacity.

   Pros: your heating system will not freeze and burst.

1. 
   WayneL5 | Mar 06, 2003 12:45am | #2

   Another pro is that such solutions often have corrosion inhibitors in them.

   A con would be that ethylene glycol is toxic, especially to pets, and apparently tastes good to them.  So if you ever had a leak and a dog, the dog may drink it and be killed.  Of course, it's used all over and few people have trouble.  Your system should have zero leaks.

   Another con is that you can't dispose of it down the drain.  It would have to be taken to an automotive shop for disposal as antifreeze.

2. 
   VtMike | Mar 06, 2003 02:20am | #3

   I use it, but only if it is really, really necessary.

   DO NOT use car antifreeze. Use only Propolene Glycol, non-toxic antifreeze designed for heating and solar systems and not the RV stuff you see in the DIY store. Before installing it, replace all the gaskets and air vents, add isolation valves and a backflow preventer. Many times I can get away with 25% solution. If all you want to do is protect the pipes in a ceiling over an unheated but insulated garage, that is enough to keep them from freezing.

   Pros: Keeps pipes from freezing.

   Cons: Leaks where water doesn't. Gums up zone valves, air vents and flow checks. Leaves a residue in the pipes. Needs to be checked and replaced periodically. Loss of efficiency. In low mass boilers it can cause surging and popping. Makes servicing and modifications more difficult.

   Before doing anything, check your local codes, boiler manufacture warranty and installation instructions.

   Yesterday I couldn't even spell plumber, today I are one.