I suspect you are suffering the from the two problems described above, low water in your tank and an empty water heater. I know those little scrappers only hold 6 or 10 gallons, but they seem to hold 50 when you are trying to get them filled in the spring.
My last camper was the worlds slowest to fill the water tank. You would put 5 gallons in and it would "burp" 4 of them back in you face. It would take hours to fill the water tank... what a royal pain!
Just keep trying to add water and open the hot water faucet in the kitchen and let it run until it quits blowing air or spitting. I drape a dish cloth over my faucet to keep from splashing water all over the kitchen.
2011 Ram Truck 2500, Crew Cab, 6.7L CTD, 4X4, 3.73 Rear