I ran across a pressurized water fire extinguisher in an antique store the other day for cheap. I didn’t know if it worked or not so I gambled that I could fix it. I already have one of these but it wouldn’t hurt to have another. I gave it once over in the store and it looked good. There was no rust that I could see and all of the parts were there.
This type of extinguisher is filled with water and then pressurized through a Schrader valve like you have on a tire up to 100psi. I put water in mine and then put about 10 psi. It started leaking around the collar nut (the big nut in the pic below) which didn’t surprise me that much. It was made in 1980 and rubber O-rings have a limited life.
I took the valve assembly back off and replaced the big O-ring with one from the hardware store.
The surface inside the neck of the water tank, called a cylinder, had some corrosion on it that I cleaned up using a little Brasso. Anything other than a clean smooth surface can result in leaks.
That’s a little better. I smeared some Plumber’s silocon on this surface and reassembled the extinguisher.
I put 10 psi back on it and heard some faint hissing from the nozzle and the Schrader valve. I removed the Schrader valve, blew it out, and put some silicone on the rubber surface. The main valve inside of the extinguisher is held closed with a spring under the brass nut seen in the second picture. I removed all of this, cleaned up the mating surfaces and reassembled it.
I put 10 psi back on it and listened. No leaks this time. I slowly increased the pressure up about 50 psi when I heard a “tink” and saw water leaking out of the bottom. That’s not good.
I took off the bottom plastic foot and was greeted with a small pinhole in the bottom of the cylinder. It looks like a little bit of rust had built up around here and weakened the cylinder. It also looks like there are a couple more bad spots near the hole.
At this point I threw in the towel on the extinguisher. Maybe I’ll run across a good cylinder in the future or find someone who can weld stainless. But for now I’ve just put it aside. You can’t win them all I suppose.