Originally Posted by DavidM
I would assume that your fire pit normally connects to a low pressure hose that connects to a low pressure regulator on the propane tank.
The connection on most RVs is a female quick connect and is low pressure. So you need a hose with a male quick connect and a fitting on the other end that will connect to your firepit. This one might work- https://www.amazon.com/GASPRO-Connec...1123884&sr=8-5
The fitting on the other end of the hose from the male quick connect looks like a female 3/8" flare fitting which may be what is needed to connect to your fire pit. But the firepit may have a 3/8" pipe fitting in which case pick up an appropriate adapter at a hardware store.
You wrote that your fire pit attaches directly to a 20# tank. This makes me think it has its own regulator. This being the case, you'll need to remove the fire pit's regulator and connect a quick disconnect hose directly to the fire pit itself. Unfortunately, this complicates things if you want to use a 20# tank on occasion.
This problem can be solved by modifying your fire pit's regulator so you can easily switch it out for the quick connect hose.
Your fire pit would then have a male quick connect fitting and your regulator will have a female quick connect fitting. Your quick connect hose would then have a male connector on one end and a female on the other.
A local propane dealer can help you sort this out if you're uncomfortable doing it yourself.