Usually short overnight cold spells will be no problem. Most tt have their pipes inside so they are not subject to the additional wind chill factor. Do you know if your trailer is a four season trailer? This means the pipes and all the holding tanks are in areas where if you are running your furnace they will get heat. This also should mean they are inside insulated areas and not exposed to the outside. If you are worried but don't want to use the pink stuff yet, use compressed air to blow out all of your water lines. Drain the water heater and then with the by pass closed ( if you have one ) open the furthest faucet and blow air into your city water hookup using no more then 40psi. You can get an adapter at Wally World or Camping World to use an air hose. Just work your way around to the different faucets until you are getting just air. Also, if you do have a hot water heater by pass valve, be sure to work that a couple of times to be sure there is no water in it ( I learned that one the hard way ). Don't forget the commode and the sprayer. Additionally, some newer tt have outside showers, so don't forget that one if you do.