From our experience, we've observed that many RVs are not winterized properly. Often we see that RV owners miss a section of water line, or didn't complete the entire process properly. Other times, someone might've helped do it for the owner. With that in mind, it's important to anticipate leaks and know how to look for them during the process of de-winterizing.
During the de-winterizing process, be sure to stay with your RV at all times just incase there is a leak somewhere. You want to be able to find it as soon as possible to avoid a potential flood. Close low point drains, water tank drain, and dump valves.
To check for leaks, look underneath all sink taps, toilet, and shower taps (if accessible). Check connections on the water pump and water heater. Look inside any cabinets where water lines may be running through, and also under the trailer. Watch for flowing water where there should be none, as you follow the steps below.