Canadian Airgun Forum

Disclaimer and Warning: Working with high pressure air is dangerous and can be deadly. Make sure you know what you are doing and that all your hoses and connectors match up and are rated for 4500 psi, even if you don't fill that high. A safety margin is GOOD.

Only posting this as an FYI, because it was a question I had in my mind for some time. Spring is also around the corner and the cabin fever is hitting hard, and so it's time to fill the tank!

Also Newb FYI: 1 bar = 14.5 PSI (approx.), so 250bar = 250*14.5 = 3600psi (approx.)

Question: Can I fill my 66 cubic foot (under pressure) SCBA tank with my consumer compressor?

It's not a silly question because the manufacturer states that this compressor isn't for large bottles. It is basically for filling guns and small buddy tanks.

Fortunately the compressor doesn't have eyes to see what type of tank it is filling, it only has the pressure of the tank to contend with.

Here's my tank. It was purchased from Wes at AirgunArcheryFun.ca Here's what it looks like:



The compressor I'm using is a "TOAUTO A1X", which is just a rebranded cheapy from China. It comes with the clamps for the car battery, but it also has an AC cord and built-in power supply.
Here's what it looks like:



Using a filter to separate the oil and water from air. I keep this one standing up, so that gravity keeps the water on the bottom.

Here's the filter ..




Filling the SCBA tank, for use by PCP guns, not for diving, was a breeze. Once connected and secured, I started the compressor so that the hose would get some pressure.

Then I opened the valve on the tank to let the air in. The compressor simply ran until it reached a temperature of almost 50 degrees. Then a manual shut-off for a 5 minute breather and the process repeated until the tank reached 3600 psi. My guns don't need anything beyond 250 bar.

Finally, the tank valve was shut, and I bled the system from the compressor, not the tank. Doing this pushed the water from the bottom of the oil/water filter and out through the bleed valve. My hand got wet! Soaked.

In summary:

- you can definitely fill SCBA tanks of significant volume with small home compressors
- a water/oil filter is absolutely necessary and don't let anybody tell you otherwise. There's LOTS of water in the air we breathe. Cotton filters barely 2 inches long don't cut it. You need a real filter. Those will run you 50-200$ and you'll need to occasionally refill the material in there.
- get the best compressor you can afford, and if you can, purchase it from a retailer in Canada. This will help with returns and servicing.
- ensure your connectors and hoses can handle 4500 psi, even if you don't fill to that level. If you are going to be cheap about something, make sure it's NOT your hoses.
- inspect all the fittings, connect everything and TRIPLE CHECK that the hoses and connectors are all secure
- quick-connect/disconnect fittings have small bearings in them, make sure your quick-connects haven't lost any bearings.
- use a water/oil separator and keep it vertical so the water moves downward. The hose at the top of the filter sends dry air to the tank.
- take your time and give your compressor breathers so that the internal temperature goes down
- do not keep tanks on your lap or hoses near your person while filling, it can lead to injury if there's a failure
- when you give your compressor a break, you can also shut your tank valve and bleed the system from the compressor's bleed valve to purge water
- once full, shut the tank valve and again bleed the system from the compressor's bleed valve. This will force the accumulated water at the bottom of the filter to rush out.
- if your compressor hose has one of those tiny cotton filters in them, inspect it and change as necessary. Hopefully that filter can catch oils and gunk from the compressor.

I was surprised at how much water came out of the bleed valve. My hand was soaked!

Next time, I'll bleed the system each time the compressor takes a break to minimize the amount of water in the filter at any given time.

That's it!

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Province: Ontario
May all who are afraid of discourse find their rights trampled further.
Cowardice is never rewarded.

I use a small compressor for filling my large tank, however - I run it for 12 minutes only, at a time, with 30 minutes to cool down between 'sessions'.
This 12 minute run is usually good for 200psi, so to re-fill a tank that is down to 3,000psi from 4,500psi, takes a couple to 3 evenings.
I do need a larger compressor, but new fly & casting rods and gear gets in the way of that purchase.

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Best Wishes
Daryl