Commonly called "Extend-a-stay" this 4 port brass tee allows you to tap off your RV's Propane tank for one of two purposes:
First, it can extend your stay at the campground or RV park (hence the name) without having to take the RV to a Propane filling facility. This is especially useful for motorhomes that have built-in tanks. Nothing is more annoying while you are camping then having to take the recreational vehicle to the propane station in the middle of your camping trip. One of the tees allows you to connect a 10 or 20lb portable Propane cylinder (the common gas grill cylinders) so that in the event the motorhome's Propane tank is empty, allws a portable cylinder to feed the coach.
Second, another tee fitting allows connection of your gas grill to the coach's Propane tank so that you don't have to carry any portable propane cylinders.
Of course, these two functions are not necessarily mutually compatible, so it is more likely you will use one function over the other. However, it gives you the flexibility to do both functions.
This device is manufactured/marketed by several companies, and I believe that the "Extend-A-Stay" name is trademarked, but like "Band-Aids" term, it has come to generically describe all of the manufacturer's products. Other popular trademarks are "Stay-Longer", "Sturgi-stay", or simply "4 port brass tee" as in the case of Camco.
In addition to the combo (two function units), versions are available that only offer Propane tank connectivity without provision for a grill connection.
I used the opportunity of the installation for a little corrosion control. There was some rust on the coach's Propane tank, so I did some touch up with Rustoleum. I could not find anything close to the color of the tank, so I made my own by mixing some black paint into white paint until I approxomated the color.
Installation of the tee was easy, although there are only minimal instructions. First and foremost, make sure the Propane valve is off. Basically, you don't need any pipe dope or tape, just tighten with a wrench. Use a "backer" wrench whenever possible (place a wrench on each side of the fitting you are tightening. Remember that the fitting attached (POL or Acme) to the regulator has left-handed threads (lefty-tightie, righty-loosie), so it is backwards.
Finally, since the coach's regulator becomes shifted forward about 6", the steel protection plate under the regulator is not long enough - and since the regulator will be exposed to the outside, I made a deflection sheld out of "King Starboard" that would fill the void in the fowared area, so that there would be some continued protection against rocks or other road hazards that might fly up from the pavement.
The wrenches I needed were a 7/8", 3/4", 9/16". and 5/15". No special wrenches are required, but I keep these four wrenches in their own bag for easy access.
One thing you will want to do is to bleed the Propane system in your coach. This is easily done by starting the range in the kitchen. You may have some difficulty in lighting the range until all of the air is purged out of the system, but let the range run until you get a good flame in all of the burners.