I have a hydronic system at my cottage. It has glycol in the pipes to guard against freezing if the house is shut down for winter, or the power goes out for long periods (which it does).

The system was installed in the early 90's and due to infrequent use nothing appears to have changed since. The glycol is green.

Question 1: Is there some place I can send a sample for testing to determine what type of glycol, and it's "health"?

Question 2: Normally the refill valve is closed and I open it briefly once or twice a year to "burp" a little water in to keep the pressure at 15-20psi. Over time this dilutes the glycol. How can I add a bit of pure glycol to bring the concentration back up--or to refill any lost to service?

I've only had the place 5 years and didn't get any advice from the seller. Oh--this is a sealed system that's not connected in any way to my domestic hot water.

 

Are you sure that’s necessary? Maybe you have a leak. I think in a closed system you don’t need makeup water unless you’ve had a leak or opened the system to make repairs. My make-up water valve has been closed for 17 years at least. The knowledgeable guys will probably weigh in.

(I know there’s a debate about whether the make-up water valve should be always opened or always closed.)

 

I would just pull a sample and use a simple automotive Meter for checking how good the mix is as far as what temperature it will be safe for. I think Preston has one for maybe 10 bucks. That many years I would probably remove it and do a flush. You can’t tell from pulling a pint or quart what crud there really is what you can tell is color which is not always a good indicator of what’s going on. I for one am not a fan of glycol up against potable water. If you’re adding fluids you probably have a slight leak.

 

With the glycol being green, I suspect it to be automotive (ethylene glycol) antifreeze & not intended for use in a home heating system. Heating system antifreeze (propylene glycol) is almost always pink.

 

 

I lose a small amount of fluid by keeping my makeup water valve turned off all the time. The pressure reducing valve has an overflow and it spits a little fluid out every now and then in response to system pressure changes, since the high pressure side of the PRV sits at zero.
i don't know how to put this fluid back in.

As for testing--i just want to be sure. Can anyone say positively that in the past 25 years propylene glycol has NEVER been green?
It doesn't matter much to me what type glycol it is other than when I add more I don't want to mix two different types.

 

For a hydronic system the relief valve spitting out fluid/water and the makeup valve admitting water alternately and continually means your expansion tank has too little or too much air.

You need to be able to measure the expansion tank pressure and the rest of the system pressure separately.

If the expansion tank pressure goes up and down matching the rest of the system pressure and you stilll get water out of the relief valve then you add air to the expansion tank.

If the expansion tank pressure does not follow the rest of the system pressure all the way down to the latter's minimum pressure then you need to vent some air out of the expansion tank.

Only add/drain small amounts at a time. This is an iterative (do a little, wait awhile, evaluate, rinse, repeat) process.

I do not know of an easy way to introduce more glycol into the system. You could cover the pitcher of collected glycol fluid with aluminum foil and save it to see if anyone else here gives any good ideas.

 

Doesn’t seem like they would have ever coded it green since conventional antifreeze has been green for a very long time and the pink color for propylene glycol lets you know it’s non-toxic. If it were me I would drain all of the green out and replace it with the non-toxic.

I think the problem is that even though the boiler system cold water supply pipe should have a check valve(s) that isolates the boiler water from the other water pipes in the house, if those valves are missing or don’t work properly, you could wind up sucking the boiler water into the pipes in the house – like when plumbing repairs are being done and some of the house pipes are drained and lose pressure.

I think that’s the reason for using non-toxic antifreeze. (I think some places require it by code)

 

Allenj,
It's my understanding that if the high pressure side of a prv is at zero then sometimes outlet pressure can be ported to the drain.
Can you verify if this is correct?