We never have a problem with mice in ours we use one of those ultrasonic rodent repellers that you plug in to an electrical outlet. We have used them for a lot of years so either we have no mice or they work. I don't remember the brand we bought but we got it at Sam's Club. We keep our rig plugged into electric when we are not using it. Oh I should add that we keep it in the rig all the time so it does it's job no matter where we are located.
Rosie, we never let the RV special antifreeze get into our water heater (it has something to do with the heater element) as it will make your hot water smell like rotten eggs. I do know that when my DH winterizes he always says how easy this one is to do it takes him very little time. I know he drains the water and our water heater has a bypass lever so it won't get RV antifreeze and when he puts in the RV antifreeze he uses the built in water pump to circulate it throughout the complete water system until the RV antifreeze runs out of each faucet which he turns on the off. When you want to use your rig again you drain the RV antifreeze which in not dangerous then flush the water lines with fresh water. The dealership will show you how to do this plus you should also receive a manual that explains how every thing on your rig works. We keep ours in our motor home because it can come in handy when you are on the road. Don't be surprised when you see the instruction manual, ours is large and thick it explains everything you can imagine.
