We were exchanging a propane tank that wasn't quite empty and I hated to waste it. This is how I transferred the extra into our barbeque propane tank. Quick and easy tutorial on how I filled one propane tank from another:
- make up a ~6' length of hose with a propane tank connector at both ends. You might have to search a bit to get one with a hose barb. One of mine did (bought in a Mexican hardware store), one did not and I had to add a pipe thread to hose adapter. Crank down on the hose clamps quite hard. This is more pressure than a boat water system for example which may top out at 60 psi.
- use hose with a moderate pressure rating. Around 250 PSI / 1.6 MPa. I used clear vinyl reinforced hose, 10mm. Larger diameters will have LOWER pressure ratings. Clear hose is great because you can see the propane flowing and also when it stops flowing
- Connect the 2 tanks with your hose
- Hang the full tank upside down in the sun (to help raise it's internal pressure).
- Have the empty tank 6' lower, and in the shade (gravity helps - propane is a liquid under pressure)
- open both tank valves
- open bleed screw on empty tank (not wide open, just a bit). You'll smell a bit of propane but it's normal
- close both valves and bleed screw when propane stops flowing.
- make sure the gas bleeding from the lower tank does not fill a cockpit with cockpit drains that are underwater. Do it on an open deck.
- no open flames. Make sure the stove is off, and nothing with a pilot light is on.
- do it downwind so propane won't flow back into the boat's interior
- if you want to be extra cautious you won't turn on or off any electrical switches or breakers because of the potential for a spark, but now you're getting paranoid.
- disclaimer: do this at your own risk. These are how I did it, and you're results may vary.
Clear hose - you might be able to see the propane here. It's clear
The bleed screw is visible right at the bottom of the valve, right in the center of the image.
Use a skinny flat head screwdriver to open.