19 year old antifreeze in CI hot water system-problem?

naivehomeowner

There is what looks like green corrosion on outside of shutoff valves on several CI radiators, which I understand can be caused by antifreeze(?) System is cast iron boiler feeding a dozen CI radiators and a hydrocoil. In basement is a tag indicating antifreeze was added in 2002 shortly after whole system was installed, pretty sure water not changed since then. I understand this was done to prevent freeze ups here in NE with brutal winters and home was 2d home with owner often away. Since then, there is a backup generator and family lives here all the time so seems like freeze up risk is remote? Anyway, wondering if that antifreeze is past bestby date and could damage system and whether it needs purge and just use new water or what is best course? thanks for any suggestions

Docfletcher

19 years is far too long to keep in a system. My understanding is antifreeze becomes acidic after 5 years or so. Acidic antifreeze will attack all the copper in the system creating pin holes etc. Get some test strips and test for and test the PH level. Should be around 7 (neutral) I think.

mattmia2

there are test strips for hydronic antifreeze, use those. Probably too old. Make sure there aren't hydroair coils in an attic or piping in the wrong place in an outside wall where it can freeze even during the period between heat calls

rick in Alaska

If there aren't any potential issues with anything freezing up anymore, it would be best to just flush all the antifreeze out and just use plain water.That way you would not have to deal with it, and water is a better heat transfer medium anyway. I would use some kind of boiler cleaner before you add the water though in order to flush out any debris.
Rick

EBEBRATT-Ed

In addition to the above comments you may need some type of cleaner neutralizer.

PC7060

I used Sentinel X400 to clean and flush my old system.  

https://www.supplyhouse.com/Sentinel-X400-1GL-Sentinel-X400-System-Restorer-Gallon

Followed up with X-100 when refilling. That was about a year ago and notice the water was still clear (ish) when I recently flushed out the DIRTMAG.  In the past, new water would turn dark pretty quickly as the O2 reacted with the iron pipes. 

hot_rod

I suppose it depends on how dependable the generator is. In an attic you have hours not days before a freeze up. Some installers put freeze stats or freeze alarms on coils when they are in locations like that.

I agree, flush that old glycol, run a cleaner, then decide if glycol is in your future

Derheatmeister

Yes your system fluid probably needs to be addressed..
When we are involved with such a system we perform the following test
1. Turbility/ Visual test
2. Ferrous material test via a magnet and strips
3. Copper test.
4. PH,Sal,EC.TDS and hardness via frequently calibrated test equipment.

We would probably address it as the following

A. For enviromental reason we would recover and recycle the Acidic Soup vs. putting it down the drain.. Just dumping Glycol down the drain can also have bad effects on a septic tank/Leach fields..

B. Flush the system with regular water to be followed by installing a system cleaner such as Fernox F5,Rhomar,Sentinel or Boilermag.

C. Flush the System cleaner.

At this point you can either run with at least 20% glycol which will eventually deteriorate and will be in need of the above mentioned Services...Again.

Or you could run with Deionized water as per VDI 2035/ANSI Stardards
When you install Deionized water i would highly recommend a Sacrificial Anode install for proper PH balance support.
I would also recommend a mixed bed inline filter for the makeup water.

Ideally with deionized water we like a PH of 8.2 to 8.4 and a EC below 100 Micro Siemens for a system such as yours.

naivehomeowner

Thanks very much for all the advice especially derheatmeister for the answers to what I was wondering for the how and what of the water add following flush and clean. The coil is in a crawlspace under living area that’s pretty well insulated so I think I’m ok w just water and leave glycol behind. Wondering too if the green corrosion on outside of radiator valves means those valves are suspect or could leak going forward? With the green visible on outside does that mean they leaking already ( don’t feel wet) ? thanks all!

Derheatmeister

Can you post some pictures showing the Corrosion..
Sometimes Corrosion is due to Galvanic reactions between two different materials..
Low PH and Oxygen ingest also can assist with the corrosion.
In order for us to lower the reaction between the different Materials we use deionized water which lowers the Electrical conductivity (EC) of the system fluid which in turn does not allow the materials to react to each other.
It is that simple..

mattmia2

It could just be a minuscule leak at the packing too. Water will evaporate, glycol will not so even a tiny amount leaking will form a stain and a wet/greasy spot.

naivehomeowner

Thanks again for the helpful info. Attached are pics of three of the valves with green corrosion, there are others but not all the radiators have them. Not sure if these are related to the old antifreeze or not, a layperson suggested that to me, which started my concerns about the whole issue. Also a pic of the tag on a pipe leading from boiler indicating antifreeze 'cryotek' added in 2002. Any advice appreciated as to if this is an issue and/or i can just leave the valves alone or any other measures. thanks

mattmia2

that looks more like it is from dampness from the outside rather than from the system. you aren't by the ocean with salt water air by any chance?

naivehomeowner

Not near ocean but typically very humid here. So I guess valves are ok whether green stains are from antifreeze or not, need to do antifreeze flush as related above in any event. Any idea on best way to clean off the unsightly green corrosion and keep it off? thanks all!

PC7060

That green buildup on bronze fitting is pretty common due to humidity. Use steel wool or the stainless kitchen scrubber pads to remove green oxidization. If there is significant oily buildup, kitchen cleaner on rag works well.

Mosherd1

you can also try Brasso cleaner/polish.  If it was me and I wanted keep them looking new, after I get them all cleaned up I’d spray them with clear satin spray paint or spray lacquer.