Majority of planted tank keepers are using Carbon Dioxide(CO2) cylinders/bottles to supply CO2 for the plants. To safe cost many are using Fire Extinguishers(FE). I’ve been using FE for couple years myself but also I’ve been getting problems with them as some of them were leaking through the valve.
Here is a method how to repair the leaking CO2 FE.

The cylinder come with 2 different valves: push and screw valve.
I’ll be showing how to repair the screw valves.

Important: The cylinder does not have to be emptied to fix the leak but for your own safety please do the work on cylinder that is completely empty.

First unscrew the top bolt, there should be a washer under it.

Now you’ll need a spaner to remove the valve. It might be very tight so you might need someone else to help you to hold the cilinder.

Here is the valve no push thesmall end to pop it out.

Now you have two parts the small bit has 2 rubber seals these are the ones that must be replaced as they are worn and cannot hold the preasure. Remove the old seals and replace with new ones.

I’ve bought a set of rubber seal in B&Q.

Once you’ve replaced the seals it is good idea to lubricate it with something. I use silicone lubricant that divers use to lubricate their gear but I think Vaseline should also do the job.
Once that is done put everything back it was(do not forget the washers)

That’s it.