CAFS Pressurized Water Extinguisher Modification

Without a doubt, one of the most common inquiries I have gotten is about how to modify a pressurized water extinguisher to create the "CAF" extinguisher featured in the video on our YouTube channel. Here is a brief article explaining it. 

With any tool modification, you need to remember that the manufacturer may not advocate or sanction the modification.  Do so at your own risk.  

The modification came to us from one of the guys I used to work with. He had worked with these extinguishers in his volunteer company and they found them to work well.  The principle of the modification is to create a class A foam extinguisher that provides a more aerated foam when discharged.  The total liquid volume of the extinguisher is only 1 3/4 gallons as opposed to the standard 2 1/2 gallons. The extra air helps to aerate the stream and expel the solution. The foam is good for increasing the effectiveness of the extinguisher as well as for laying down a barrier to help slow and stop brush fires when hose lines cannot be stretched fast enough. Every engine in our firehouse has one of these extinguishers along with standard water and other special agent extinguishers. Our brush rig has two of them. 

The modification is fairly simple. The steps are as follows.

1. Mark the extinguisher properly.  Since we do not carry AFFF foam extinguishers, we marked them red with "FOAM" on the tape stripe
2. Discharge the entire extinguisher and disassemble it
3. Remove the pickup tube and head assembly
4. Drill a single 1/16" hole at the top of the pickup tube, no more than 2" from the top where it connects to the head.
5. Measure 1 3/4 gallons of water in a pail and fill the extinguisher with it.  A large funnel helps.
6. Add 4-8 Oz Class A foam (depending on how bubbly you want it)
7. Reassemble the extinguisher
8. Shake vigorously
9. Repressurize to the recommended pressure (usually 100 PSI)
10. Deploy your CAF extinguisher!

Take note that you do not need a foam tip for this to work, although the use of an aerating foam tip that is normally supplied with pressurized AFFF extinguishers will create even better foam.

*Follow appropriate refilling precautions as recommended by the manufacturer*

Place a marking band of tape on the body of the extinguisher.  We chose red and lettered it as "Foam". 

Drill a single 1/16" Hole in the pickup tube about 1-2 inches from the top.  This hole must be above the water line.

Mark a pail or bucket at the 1 3/4 gallon mark (7 quarts or 6.62 Liters).

Mark the handles with colored take to indicate the agent.  Here blue is water, red is foam and purple is Purple-K

Thanks for stopping by and be safe out there.  -MG