I am freaking out! The temperature got down to 25 last night and we have water in our water heater and one gallon of water and a chemical in our black tank. We did blow out the water lines. Should I be concerned about the tank and water heater freezing last night? We were not expecting the temperature to drop so fast. We are camping and I am scared I am going to find a busted tank. —Rhonda F.
I doubt any damage was done with one night below freezing, but if the temps are due to dip that low again, you’ll probably have to fully winterize the RV, including the water heater. If you have no water in the hot lines, the only way to blow out all the fresh plumbing lines with the water heater filled is to bypass it via the bypass valves. Perhaps you only need to drain the heater and all will be fine. You can easily drain the water heater by removing the plug and opening the P&T relief valve on the unit. But do verify all plumbing lines are clear of water — both hot and cold.
The holding tank is likely just fine also. Freeze damage occurs when lines freeze and expand the tubing. One gallon of water in a holding tank, even if it ices over, will not expand enough to cause any damage. It may cause the termination valves to stick a little, but nothing should be hurt. But it might be time to decide to move the RV or fully winterize it if the temperatures stay below-freezing for any length of time. No need to freak, however.