Replacing Glycol in a System Chiller

[Broothru]

It recently occurred to me that I've never drained and replaced the distilled water/propylene glycol mix in my chiller in the five (or so) years I've had mine, pre-Covid. I was reading that it's good practice to replace with clean fluid every year, though I'm not sure exactly why. It's a closed loop system circulation using distilled water and a non-toxic/non-reactive fluid with a low freeze point. As long as there's continued cooling performance and no algae growing in the tank, what's the point?

The tank level hasn't changed that I can tell, since I first filled it. I haven't observed increased cycling of the chiller compressor or increased lag times when selecting a lower temperature. I'm almost tempted to not tease the animals at this point.

Two complications going forward caught my attention: 1) there appears to be no low point drain to empty the tank. I guess I could repurpose an old auto-siphon I've got lying around from the days of glass carboys and plastic brew buckets; and, 2) the price of new glycol.

When I first got my chiller, I ordered 2 gallons of glycol from a chemical supplier on line (Houston, maybe?). I doubt I paid more than $20-$25 per gallon delivered to my door. Then yesterday I saw an 'add-on' to a Spike chiller for a 2½ gallon jug of glycol for $160 bucks! I mean, like WTAF? It's not like we don't have chemical plants in the U.S. producing this rather mundane product, so tariffs can't be the excuse. What am I missing here?

Propylene glycol mixed with hot water was the same mixture we used for de-icing airplanes back in my working days, and I guaran-damn-tee the airlines weren't using $80 a gallon fluid to make my B-777 safe to fly in a snow storm, 'cause we'd use at least 80~100 gallons, sometimes twice, per each trip.

 

[shoengine]

Does it smell bad? Anything floating in it? I changed mine after three years but I don't constantly keep mine cold.

https://www.homebrewtalk.com/threads/propylene-glycol-smells.735064/

As for cost, I think gallons are around $35 on Amazon. 5 gallons for $120.

 

[Broothru]

Does it smell bad? Anything floating in it? I changed mine after three years but I don't constantly keep mine cold.

https://www.homebrewtalk.com/threads/propylene-glycol-smells.735064/

As for cost, I think gallons are around $35 on Amazon. 5 gallons for $120.

No off-odors, not cloudy, no floaters. A bit of green copper oxide buildup on the top few chiller coils, so I guess there’s been some evaporation of water.

$35 per gallon seems a bit high for glycol, but sounds much better than $160 for a 2½ gallon jug. I don’t leave the tank turned on all the time, but on average I brew once per month so it’s working ‘frequently’. My brew space is generally low to upper 60s year ‘round.

 

[cfrazier77]

I have always used rv water line glycol. It is propylene glycol, human safe, and costs $5 a gallon. I still need to dilute it so it is even cheaper.

 

[Broothru]

I have always used rv water line glycol. It is propylene glycol, human safe, and costs $5 a gallon. I still need to dilute it so it is even cheaper.

Wow! I never thought of that, even after 15 years of RVing and winterizing every season. I’m quite familiar with RV/marine use water treatment antifreeze, but just never made the connection between it and glycol chiller fluid.

Oh, DUH!

 

[Broothru]

I have always used rv water line glycol. It is propylene glycol, human safe, and costs $5 a gallon. I still need to dilute it so it is even cheaper.

IIRC, undiluted RV waterline antifreeze has a freeze point of ~20F. That’s a lot colder than the coolant in my chiller, so distilled water dilution will save even more $$$. If I’d thought of this chiller hack myself, I could have saved a ton of angst. RV antifreeze. Brilliant! And so obvious, that I’m embarrassed.

I’ve set the hysteresis values on my setup to switch the compressor ON when tank temperature exceeds 34F and kicks OFF at 26F. This allows for very rapid cooling without putting a lot of load on the compressor. It also doesn’t cycle on/off as frequently as ‘tighter’ settings.

 

[SanPancho]

IIRC, undiluted RV waterline antifreeze has a freeze point of ~20F. That’s a lot colder than the coolant in my chiller, so distilled water dilution will save even more $$$. If I’d thought of this chiller hack myself, I could have saved a ton of angst. RV antifreeze. Brilliant! And so obvious, that I’m embarrassed.

I’ve set the hysteresis values on my setup to switch the compressor ON when tank temperature exceeds 34F and kicks OFF at 26F. This allows for very rapid cooling without putting a lot of load on the compressor. It also doesn’t cycle on/off as frequently as ‘tighter’ settings.

there's more than one RV option. some use one of the glycols with alcohol, and some dont use any at all, just alcohol. there is another one out there that is propylene and i think ethyl alcohol, so technically is 100% non toxic. i just buy the cheap $2 gallon at walmart of the pink kind. if there's ever a leak, you'll see the color change in your beer.

otherwise, glycol is a perpetual fluid. it doesnt evaporate. but you should check your % once a year to make sure you havent evaporated the water portion, which would increase your glycol ratio and decrease your chilling ability. no bueno for your refrigeration unit.