Reduction of air pump for aeration septic tank

Septic tank air pump output is constant in general, in order to reduce the amount of aeration is not only lower the voltage inverter and transformers or control equipment installed or to install air relief valve. In any case it is not easy.

The need to change the amount of aeration septic tank air pump

If an abnormal amount of air aeration septic tank expression, or excessive and the amount of scum, and to smell. The proper amount of aeration depends on temperature.

I thought about how to lower power consumption and easy way. Here it is used in septic tanks since 2000. This way I can now ease the management of septic tanks. National Air Pump CL2329 (diaphragm, air volume 40 l / min, 40W), but the idea is the same in other models.

Not only by lowering the voltage of the septic tank air pumps, electrical products to reduce the problem, not the output it is possible to apply this method. Large resistive load power factor will not be any problem. However, please note the size of the capacitor voltage and current.

Material and equipment fabrication method of reducing the amount of aeration septic tank air pump

This photograph is the device. It made it with the capacitor 1 piece for each, 330kΩ1/4W 1 resistance, 1 switch, and connector of the code of 4μF200V, 6μF200V, and 8μF200V.

6μF, 8μF, and 330kΩ are made parallel and the capacitor of 14μF is made. The switch and 4μF are made a series and it connects it with the capacitor of 14μF in parallel.

Next, the code connector is only installed. The capacitor is only made to work by installing it the series in the air pump of the septic tank in short. To switch the capacity of the capacitor, the switch is turned on.

It is switched to 14μF and 18μF by this. Resistance is for the electrical discharge of the capacitor when this device is removed.

Theory of aeration amount decrease (power consumption decrease)

Theory of aeration amount decrease

R, L, and concept of impedance of C series circuit

An electric circuit of the air pump of diaphragm type's septic tank can be considered that resistance that the inductance of the coil is the main and is small is in the series. To connect the capacitor with the series and to decrease power consumption to this, it planned.

Resistance R resistance is assumed to be red vector OA in a left complex impedance chart. The reactance of the coil corresponds to vector AB in blue + jωL. Therefore, the resistance of the exchange of this air pump (impedance) corresponds to the length of vector OB. (Moment of force is cosΦ1. )

The reactance of the connected capacitor is j(1/ωL) in the series in this air pump - of green It corresponds to the length of vector BD and it has a negative value. When you connect this with the series It becomes the vector of O-A-B-D and it becomes impedance that corresponds to the length of vector OD in the synthesis. (The moment of force of the synthesis is cosΦ2. )

It is time when it is necessary to take care is near the absolute value of the reactance of the coil the reactance of the capacitor connected with the series. It is a thing that reactance is counterbalanced at this time, the resonance happens, it becomes only resistance's worth, and an excessive current flows.

(ω=2πf   f is a frequency.)

This device is attached to an air pump

This device is attached to an air pump

The vinyl tape is wrapped around the whole and it insulates it. This device is installed between the air pump and the power supply as shown in the photograph.

The film of rubber of diaphragm is moved with the electromagnet of the exchange and diaphragm type's air pump is moved as a pump by the valve's working. Inductance is late and a lot of current phases are late in the circuit because of the one like the coil compared with the voltage phase.

The entire circuit is made capacitive by putting the capacitor with small capacity in the series as it is not easy to put the coil though it is general to put the coil in the series. The current phase advances compared with the voltage. Moreover, the capacitor doesn't consume the electric power.

Operation measurement before and after change
Power supply
Voltage of
air pump
it changes
102V 1.37A 140W 0.29 40W 102V
Series capacitor
102V 1.02A 104W 0.22 22W 79V
Series capacitor
102V 0.65A 66W 0.15 10W 51V
The measuring instrument It uses it as   METEX M-3860M wattmeter.


The model of the air pump must change the capacity of the capacitor. Please decide capacity after it experiments with a small capacitor of capacity. The resonance is caused with the coil of the capacitor and the air pump (for inductance) when the capacitor is enlarged too much, and there is a possibility that an excessive current flows.

Please stop taking, making the capacitor a series because there is no suitable capacitor, and making it. The capacity of the capacitor might come to grow if one capacitor is short-circuited like the above-mentioned.