The issues of influence of soil moisture, heat insulation type and heat carrier temperature on heat losses of district heat supply networks pipelines are considered. Calculations were carried out to change the efficiency of insulation of polyurethane foam and polymineral foam for four different modes of operation of district heat supply networks pipelines with gradual moistening of soil from 0 to 48% with channel-free lying; insulation is not wetted. The reasons and consequences of different temperature levels in district heating networks in Russia and Western Europe are considered. The calculated distribution temperatures in the central heating system pipeline were 75.85/49.85°C. The results show that the thermal losses of the pre-insulated pipelines increase many times depending on the soil moistening. In addition, calculations showed that in absolutely dry soil heat loss of pipelines of heat networks laid channel-free for all considered modes is less than calculated. But absolutely dry soil is a condition characteristic of deserts rather than the Middle Volga region.