The question you pose is a difficult situation for both the home inspector and buyer. To properly winterize a home the following procedure must be done:The water supply to the home must be turned off.The water heater must be shut down (power or gas to unit turned off).The water heater must be emptied through the drain bib at the bottom of the water heater tank to the exterior of the home. A hose is required for this procedure and the water will be very hot if the water heater was in operation.
Starting at the upper level of the home, if a two story home, all bathroom sinks, bath tub and shower faucets must be opened to drain and the toilets flushed.Then the lower level of the home all sink, bath tub and shower faucets must be opened to drain and the toilets flushed.All of the exterior and laundry hose bibs must be opened to drain. Donít forget the ice maker line if one is present. The laundry and icemaker line will require a hose or bucket to catch the water.Any residual water left in the lines will have to be blown out with compressed air to guarantee the removal of any trapped/remaining water.All of the sink, bath tub, shower, kitchen and laundry sink traps must have anti-freeze added to the drains. The anti-freeze must be an RV type of anti-freeze and not an automobile anti-freeze.All of the toilets must also have anti-freeze added to the bowl and tank if any water remains in the tank.It is important that water remain in the drain traps and toilets to prevent sewer gas from entering the home.
De-winterizing a home is very simple: Close the drain bib on the water heater and the exterior hose bibs.Open all of the sink, bath tub and shower faucets.Make sure the laundry and ice maker valves are closed.Gently open the main water entry supply valve.The air in the water heater and the lines will be evacuated during this process and may make a loud rushing sound until the water heater and lines fill.The surge of air and water may dislodge sediment and mineral deposits in the water heater piping and may clog the aerators and low-flow restrictors on the plumbing fixtures. Be prepared to clean them, this is especially true if the house has galvanized steel pipes.Be prepared to run through the house as the lines are filling looking for any leaks under sinks and at plumbing fixtures.Lastly open the exterior hose bibs, laundry and ice maker lines to evacuate any trapped air.As you can see this is an area that is beyond the scope of a home inspector and arrangements should be made by your agent to provide the ability of the home inspector to perform a complete inspection. The seller is typically required by the purchase contract to have all areas of the home accessible and all utilities on.