Sunline offered an optional grille to be hooked to that line. It was a low pressure grille, and came with appropriate quick connects.
If your existing grille already has a regulator built into the line, you can't hook it directly to that low pressure pipe on the trailer. A grille that has a regulator on the propane line needs to be hooked directly to a tank so that you're putting high pressure into the regulator which then steps it down for the grille to use. If you hook the grille's regulator to the low pressure line, it further reduces the pressure to an unuseable level.
If you have a low pressure grille that does not have a regulator on the line, you can get male and female quick disconnects designed for propane. One goes on the hose, the other on the end of the pipe. You may also have to purchase some adapters to go from the NPT of the pipe to whatever the quick connect wants, and an adapter to fit the hose to the other quick connect.
Optionally, you might want to spend the extra money and get a quick connect system on your grille so you can remove the line that hooks to a tank when at home, and have a custom hose made up with quick connects on both ends.
Your local welding supply shop will have variety of connectors and adapters for propane. A full service propane dealer may be able to help as well. A refill place won't have the resources to help.
Or, you can install a fitting on the TT's propane system that is inline between the tanks and the regulator. This gives a high pressure fitting that can then be connected to most anything. I installed one of those for extra flexibility but find that I have only used it once or twice in 7 years.
I have a Coleman camp stove and a Coleman "Road Trip" grille that both need high pressure straight from the tank as do my propane lanterns. I have a variety of hoses and manifolds that I carry that allows me to set up a large outdoor kitchen with adequate lighting. But I will readily admit that it is usually easier me to carry an extra tank or two so I can place the kitchen where I need it and not right next to the TT.
In summary, you need to figure out what you have in the way of grilles and what you want to hook up to what. Or let this determine what you purchase in the way of a grille.
'12 F250 4x4 Super Duty PowerStroke 6.7 diesel
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