I already have two Amerex 240 water extinguishers along with a few dry Chem types. I prefer the water ones due to sheer size, simplicity and minimal mess cleanup. For most fires in a residential setting I think they are far superior to any other type.

I am building a detached shop for my new home and want to keep another 240 out in the shop for whatever may arise. Primary concern would be a grass fire. Problem is, my shop won't be heated so I need to put something other than straight water in the extinguisher.

Anyone been down this road before? I don't need any fancy expensive mix I was thinking washer fluid (flammable?) Or add in antifreeze or straight propylene glycol. The indoor Temps are unlikely to ever get below 0 degrees F.

The less toxic the better.

As an aside, anyone got a lead on best prices for an Amerex 240? Last ones I bought were 110 dollars each now best I can find is closer $170.

I’ve got the same tanks and I run the pink RV antifreeze in mine, haven’t had an issue.  Costs about $8 to fill one up.

Edit - looks like RV antifreeze shouldn't be used.

From:  https://gegcalculators.com/freezing-point-of-water-under-pressure-calculator/


Isn't higher pressure one of the reasons water remains liquid under a frozen lake's surface?

I was under the impression that water remained under the ice since the ice floats and creates an insulation barrier. You should see the gap between the water and the ice when a reservoir lowers its water level. I haven't seen it freeze there. By the way, thanks for the link. very informative.

How much lower does the freezing point of water become if you add a couple of drops of dish soap?

I found this:



On this site: amerex fire extinguishers

I did see amerex makes a special charge but it's very pricey. In an official capacity you don't want the liability of putting in some random cocktail. In an unofficial capacity the empty extinguisher alone is already a pricey item.

I didn't think of rv antifreeze that's used for winterizing that's probably my best option.

I did also consider that distilled water can be super chilled without turinng solid and the pressure may have an effect but I don't want a phase change from liquid to solid right at the moment I go to start spraying water!

Will you have power in the shop?

If so, wrap with heat tape and plug it in.

We added dish soap to our water fire extinguishers that were mounted on the exterior of our apparatus.  Winter usually kept the fire truck out on the roads for hours on end due to all the calls for service.  The soap would help to prevent them from freezing.

I use RV antifreeze in my fertilizer pumps for winter, available for -50° for about $5 a gallon.

I thought that pretty much all anti-freeze types were flammable.   Digging in to that I found this:  "RV antifreeze is made from propylene glycol which is flammable if it reaches 210 degree Fahrenheit and when burning, the gasses emitted can be poisonous."   Do you have information that contradicts this?  Thanks in advance.

It looks like @2Hut8 is correct on this, and RV antifreeze shouldn't be used.

Well so much for the glycol...

Looks like potable water rv antifreeze uses ethyl alcohol instead and appears even more flammable. That could actually be fun, like a flame thrower on the cheap... Further testing may be required.

We used to run washer fluid in sprayers, it cost quite a bit less when buying 55 gal drum. Probably not a good idea for fire extinguishers though.

That wouldn't be pleasant to learn during an actual fire.

Salt, Sugar, anything that will dissolve in water will lower the freezing point to some degree.  Pressure also lowers the freezing point.

Will you have power?
If so maybe a small insulated compartment for the extinguisher with a small lamp to keep it from freezing.

This may be the best option, acquire or make a fire extinguisher cabinet similar to those found on the walls of schools and other commercial buildings that want the fire extinguisher protected from tampering, insulate it and put a small heat source in it.

Or find out what the amerex antifreeze charge is (MSDS may clue you in) and experiment with your own cocktail.

You might also check into how fire fighting foams will alter freeze point. It won't actually make foam out of a non-foaming extinguisher but it's safe to put on fires (doesn't make it worse or produce hazardous/toxic fumes).


As for affordable water extinguishers, watch marketplace, ebay, Craigslist, and university surplus auctions. I slowly acquired used equipment via the first 3 until I encountered an auction at the local university. IIRC, I got 14 water cans, 11 large (20-30 lb) dry powder ABC, and 16 large CO2 extinguishers for ~$400. They were selling them because the manufacturer went out of business and the parts dried up so their service company quit servicing all extinguishers of that brand even if they didn't need parts. The water cans are so simple they aren't likely to need parts and if they do many Amerex parts will fit (one even came with an Amerex valve assembly on it).


I'm "currently" working R&D on a way to make foam from a water can. I know Amerex has a foaming water can but it uses a proprietary charge that is quite expensive. I had an idea on how to not require an expensive charge chemical, just a special charging process. Life got busy and I haven't done as much R&D as I wanted. I still have ~30 water cans in my shop waiting to be converted if I figure it out.


Oh, and don't overlook the blue & white water mist extinguishers. They're way more conservative on water and last a lot longer. You don't have the long range of a normal water can but they're very effective for smaller, more widespread fires like the grass fire you mentioned. I have battled grass fires with water cans (controlled grassland burns that got out of hand) and I would 100% take water mist over normal water cans to fight grass fires. Water cans, even with a finger over the end to fan the water, tend to blow the water on too heavy, placing a more narrow band of water that penetrates through the grass down to the soil where it doesn't do any good. The mist doesn't penetrate too deep, it's thousands of small droplets that place a wide band that wets more grass. All of my water mist units (7 or 8 total) came from ebay for under $50 ea by being patient. ETA, mist extinguishers are supposed to be charged with a charge of deionized water but that is solely to earn the electrical rating. If you aren't using on electrical fires, and only at a home setting you can charge with normal water. I also forgot to mention that they don't have a Schrader valve on the side (so the user isn't tempted to refill with plain water), they require a special charge adapter that attaches in place of the hose/wand to charge with air. I made my own in my shop with a little brass but they are available for about $30 from a supply house that carries Amerex products.

Thanks I actually ordered my 240 today with a 20% off coupon from Zoro.

Still undecided on what to put in it. There will be power in my shop so I can keep it heated i just dont like relying on outside input for something like that. I've been keeping water bottles in the shop in a cooler and they have yet to freeze so perhaps something as simple as a box with a small light bulb is all I'd need.