The answers you have gotten are all good but it doesn't sound like you understand how your LP system works and that could be dangerous. The large LP tank on your trailer provides high pressure unregulated gas ranging from 10 psi to 120 psi. In order to use it inside for heating cooking, etc it must be brought down in pressure. You probably have a two stage regulator which is fed by the main tank. It is two regulators attached together The first regulates the tank pressure down to about 10 psi, the second down to about 1/2 psi (11-14 inches WC) which is what enters your trailer and includes the grille quick connect on the side of the trailer. Attaching a grille that already has a regulator on it, namely the ones that use the small bottles, will not provide sufficient gas to the grille. They will work, but at a reduced heat. So to use those grilles you must remove their regulator. The Weber series seem to be the most popular and easiest to modify.
Now if you don't wish to or cannot remove the regulator then a device like the Extend a Flow comes into play. It fits between the trailer LP tank and regulator. So it provides high pressure unregulated gas to the grill, like the small bottles, and uses the grilles regulator to control gas flow.
The real danger is you just never connect high pressure gas to a non regulated device, you will then have a blow torch.Internet advice is helpful but I would suggest you check with a certified propane location to verify that what you want to do is safe.
Is that something I would plug into the gas output on the camper or to the actual tank?
I have the extend a flow kit but that is NOT what you want since you already have the quick disconnect on your trailer. The Extend A Flow kit is for coming directly off your trailer tank with the supplied Tee adapter. You don't need that.
One way to make this simple is to remember you only want one regulator in the line to the bbq. Your propane port on the side of your trailer comes off the regulator in your trailer. Most all bbq's come with a regulator. That would give you "2" regulators in the line which might provide too low of propane pressure.
Here's what I would do; If you don't have a bbq already, get something like the Weber Q series and remove the Weber's regulator. Next, get a quick disconnect propane hose to fit the port on your trailer along with the necessary fittings to adapt the hose to the propane inlet to the Weber, which will now just be a threaded hole because you removed the regulator. That's what most folks on this forum have done and if you do a search you fine a lot of posts with pics, description of fittings, etc.
The other option like posted above is to just carry a small portable propane tank and hook up to that.
If you want a great RV BBQ. Go out and grab a Weber Q100. Unscrew the regulator, go to your local hardware store, and grab the correct fittings (1/8 npt X 3/8 npt and a 1/8" npt pipe nipple, I think). Thread it all toegther and get a Campgrill quick connect by 3/8 extension hose.
Voila - A better grill (albeit small) than most folks have on their deck at home.
Ignore the know it alls who say it won't work and have never tried it. It works, and the Q will hit 600 degrees. You can sear a steak, cook potates, and BBQ a burger as well as any grill. The Weber rocks, and mostly because the cast iron grates.
If you are going to try and use your grill "stock", and it has a built in regulator, you cannot use the quick connect on the side of your trailer. Can't be done (effectively) no matter what connector assembly you use. If you are going to use the grill with its own regulator, you have to "T" into the high pressure line between the tank and trailer's own regulator assembly so that you get unregulated LP to the grill. Can be done and many people use said adapters, the most popular being Stay a While or similar, either the whole kit or just the "T" and you supply your own hoses.
If you want to use the low pressure "quick connect" fitting on the underside of your trailer with your grill, you can't use a grill with a regulator still attached. You either have to buy or have a grill designed for RV low pressure use (a lot of trailers come with one) that already has the regulator removed or you have to have a grill that is built such that the regulator is separate from the gas control valve and can easily be removed...the Weber Q series of grills are one such and are very popular. Easy to convert, well made, compact and they cook quite well.
Here's a post the I had put up on the 5ver page concerning the conversion:
Here is a site that sells any of the above pieces of "conversion" equipment you might need, from the Stay a While type "T" connectors and hoses, to the conversion pieces you might need if you are going to remove the regulator from your current grill (you don't mention the brand of new grill you have; it may or may not be a candidate for conversion):
Again...if you are going to use your grill with its regulator attached, you have to tap into the line between one of your supply tanks and the trailer's regulator or you have to remove the grill's regulator in order to convert it to use the low pressure quick connect on the trailer.
My 2 cents, your mileage may vary...
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