In a feeding pump it is not quite as crucial – in contrast to the metering pump – to deliver a precisely dimensioned quantity of fluid. Additional sensors are used to monitor the delivery rate. This information is then used to regulate the delivery period of the pump.

In general Thomas pumps are metering pumps, as a defined stroke volume is delivered with each solenoid stroke.

The reciprocating pump is a metering pump, which handles the functions of all otherwise necessary system components such as a pump, metering valve, shut-off valve and possibly a pressure sensor – all at once.

Certain diaphragm pumps can also be described as feeding pumps. These can be used to cope with specific medium requirements. Generally, however, this pump can also be replaced by a reciprocating pump.

In a diaphragm pump the diaphragm is directly or indirectly moved by the solenoid plunger, enlarging the pump chamber. The supply of liquid is controlled by check valves at the inlet and outlet. The pump draws in the medium during one plunger motion and delivers it against system pressure during the return motion.
By selecting an appropriate diaphragm material and hydraulic connections, the pump can be adapted to suit the particular medium.

In addition to diesel and petrol/gasoline, Thomas pumps can handle fuel oil, ethanol, sea water, acids and alkalis.