propane outlet

I want to know what it would take to create an outlet to fill portable propane tanks off of an existing propane system. I have propane in my house and I would like to have an outlet to plug into to fill portable tanks rather than paying to swap them out at the store. I'm thinking I would need a compressor. Anyone know gas?

Your problem is getting liquid propane from one tank to the other. The delivery truck taps its tank from the bottom to get the liquid into your house tank. Your house tank taps from the top to deliver vapor for you to use. You either need an expensive compressor, turn your tank upside down (don't even think about it), or a different tank.
If you need to fill a tank for a vehicle, another tank with a vapor powered pump is the way to go. We had this setup on the farm for a tractor years ago.
If you just need to fill tanks for a grill or such, you should consider a direct line. I've got a line to a box on my deck and just connect my grill and burner directly. Haven't filled a tank in 5 years.

Does your pig (big tank) have a couple fittings on the top with nothing connected to them? That is where you can have a fill hose installed. It has a dip tube to pull liquid from the bottom.

Do you own or rent your tank? If you own it, you can buy the parts on ebay and go to town. If the gas company owns it, they may have a say in who and how and if you install it.

It is NOT CHEAP and a direct line is probably cheaper for just a bbq. The fill hose doesn't make a lot of financial sense unless you have an LPG vehicle or lots of small tanks to fill.

thanks guys. this should get me going in the right direction.

What you want is often called a "wet leg" and is a second port on your main tank with a tube that runs to the bottom of the tank. You cannot expect to get anyone to install on onto a tank that you cannot prove that you own, at least not a professional. And do not do this yourself, nor should you pay some redneck to do it for you. The wet leg port works with a special set of hoses, one with liquid propane to your to-be-filled tank from the wet port, the other is vapor coming from your empty tank to your main tank via your regular gas port (where your regulator is connected). A quality set includes an little electric pump to move the liquid propane, a cheap set uses a check valve on the gas side, and a push button vent to let out propane, in order to start a siphon. Any set should have valves on the business end of the wet lines at least. This is dangerous business, and most states require some degree of training in handling propane to legally aquire and install a wet leg. Also, you don't want to install such a thing onto your main tank except when the volume of gas is very low; as removing liquid propane, installing the wet leg, purging the tank of oxygen, and refilling the tank is something that professionals should do and the more liquid that is left the more work that is to be done.

bingo! wet leg got the answers. jargon is key to google searches. before i knew the word permaculture, it was very hard to find info when all i had to look for was a vague idea i had.