I second WrkerBee's comment. EVERYTHING needs to be checked. Things that were wrong with my new Sonic:
1. Almost every "twist-on" plumbing fitting was loose. That is where the PEX piping has a fitting that screws onto something else, like faucets, the back of the toilet, water heater. They should be finger tight + 1/4 turn with pliers. I had leaks under my kitchen and bathroom faucets, behind the shower faucet (which requires cutting the seal and removing 2-3 screws to pull the faucet away from the wall), and at the back of the toilet.
2. Window screens were not snapped in all the way onto the window frames. I bent one of the clips when trying to get one screen clipped on all the way, and cannot find a replacement - have the dealer do it if you find loose window screens.
3. The trim around the roof vent fan was buckled and had a screw missing.
4. One of the buckles holding an emergency exit window closed was raised on one side. One of the mounting screws for the buckle had stripped out and the hinge arm on the inside of the buckle was bent. When I found it, I straightened out the arm on the inside of the buckle and used a slightly oversized screw to replace the original.
5. Might be a good idea to have the dealer show you the tire pressures on a gauge. Your trailer will likely come with green valve caps and nitrogen filled tires. Just completely ignore that - it's nothing but a gimmick. Just use regular compressed air to top off your tires as needed.
6. Make sure everything works in all modes, for example refrigerator works on electric and propane.
7. If you don't know how to operate the water heater, have them show you. Just don't turn on the electric side if there is no water in it! Also have them show you where the bypass valves are for the water heater for winterization. There may also be a tube for sucking in antifreeze using the water pump. Have them show you where that is, if you are interested. As well as locations of low point drains and freshwater tank drain. Sewer dump connections/valves.
After delivery:
8. If you have the Lippert In-Wall Slide System (formerly known as Schwintek), there will be aluminum gear rails on the sides of the slides. Those need to be lubricated with dry spray-on lube containing PTFE. WD-40 makes a dry lube with PTFE that I use, there is a Blaster brand, and more expensive lubes that are the exact same stuff but more expensive because they have "for RV slide use" on the label. You can get it at auto parts and hardware stores.
9. You need a good tire pressure gauge. I recommend the Slime Elite pressure gauge as it has the least amount of air loss when checking tire pressures. I also recommend that you get a collapsible lug wrench with 4 or 6 reversible lug sockets and make sure one of the sockets fits your trailer lug nuts and your tow vehicle lug nuts. It is a good idea to also have a 150 ft-lb torque wrench to verify lug nut torque, but you can usually just pull into a tire shop parking lot and they will check lug nut torque for you. If you have your own compressor, I recommend an inflator with a built-in digital pressure gauge. I have a cheap one from Amazon and it is super convenient, and the pressure reading on the inflator gauge matches exactly the readings I get from my TPMS.
7. Speaking of TPMS - if your trailer does not have Tire Pressure Monitoring, I highly recommend that you add a TPMS system.
Make sure to take a set of wheel chocks with you. It sucks to get home or first parking place and discover you don't have wheel chocks. And also your choice of leveling device. I like the curved ramps. And a level.
