This assembly allows the bearings to be lubricated by oil, as hot water may not provide adequate lubrication. A variable-speed drive set just below the motor on the surface, can be used to regulate flow instead of just turning the pump on and off. If a lineshaft pump is used, special allowances must be made for the thermal expansion of various components and for oil lubrication of the bearings. These pipelines carry fluids from the wellhead to either a site of application, or a steam-water separator. The cost of transmission lines and the distribution networks in direct-use projects is significant.
Conventional steel piping requires expansion provisions, either bellows arrangements or by loops.
In addition, the piping would have to be placed on rollers or slip plates between points. When hot water pipelines are buried, they can be subjected to external corrosion from groundwater and electrolysis. They must be protected by coatings and wrappings. Concrete tunnels or trenches have been used to protect steel pipes in many geothermal district heating systems. This distribution system is generally preferred when the geothermal energy is abundant and the water is pure enough to be circulated through the distribution system.