Water holding tank/water pump

[arturob]

I have a cougar 322QBS and I'm a complete novice at trailer camping. I bought the unit second hand so I didnt get very much instruction in how to operate the unit. My current problem is trying to get the water storage system to work when boondocking. When I tried to fill the holding tank I very soon saw water flowing out of a plastic tube at the rear of the trailer. I wasnt sure if this was a drain tube with a missing cap or an overflow. I called an RV dealer that sells Keystone and one of their techs suggested this was probably an overflow. The gauge lights inside on the control panel are telling me the storage tank is empty however. When I turned on the water pump I did get some water but it quickly dried up and then I got lots of gurgling then a spurt of water again then more gurgling and air coming out the tap. I am guessing that I have an empty tank and that what I thought was an overflow is actually an uncapped drain tube. Anyone have a similar unit that can tell me whats going on?? The manual that came with the trailer is a joke and hardly has any information. Thanks in advance for any suggestions