Warranty Service Charge

Hello all. My name is Alan and I purchased a R-179 in late Dec 2016 from Atlantic Marine & RV, Ft. Pierce, FL. I have enjoyed the little trailer for about 22 nights already this year, using it at several campgrounds and boon docking for up to 3 days at a time. Very nice trailer and perfect for my needs. I did discover a very minor leak in the black water tank where the flush fitting enters the side of the tank. FR has already approved a warranty repair. I took the trailer back to Atlantic, and to my surprise, they demanded a $110 upfront payment before they would take the trailer and do the warranty repair. I said no and brought it back home. So I turn now to this great group of r-Pod experts - is this a normal requirement to have warranty work performed? What is the purpose of such a payment? Does anyone have any suggestions? The ultimate goal is to stop the leak.