 Many Nordic Countries utilize vacuum sewers, it is helpful to have some type of marker or monitoring to locate valves when they are buried under the snow for extended periods.With lower population densities, the costs for the collection chambers and vacuum stations are less important than the costs of installing pipe and, for gravity sewers, pumping stations, etc.. Pneumatic pipes are generally smaller than gravity-drained hydraulic ones In frost-free climates, the pipes for a vacuum system can also be buried more shallowly than a gravity system.High specific conduit lengths, where the required pipe length is longer than ~4 metres per inhabitant, will tend to make a vacuum system cheaper.