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When you need a drain pump with a float switch

Drainage pumps with an integrated float are used for installation in tanks, storage tanks, tanks, wells and other structures. Several floats can be installed in one tank with different functions: pump control, liquid overflow sensor, emergency level sensor.
When used, pumping equipment is protected in the "dry running" mode, and protection against overflow when filling the tank. How to use the device with your own hands offers to get acquainted with this article.

Purpose and principle of operation of drainage pumps

Floatless are necessary for use in summer cottages and household plots, where they save their owners from many unpleasant problems. The main task of the devices is to ensure the removal of rainwater, wastewater, pump out melt water from basements, cellars, wells, ditches, pits.
A drainage floatless pump is used when pumping water from a pool, pit, artificial pond. Special modifications of drainage units allow pumping out contaminated water.
In a minute, a drainage pump, with average technical characteristics, can pump out approximately 180 liters of water. The power of the device decreases with immersion and the distance of the location of the pumping point.

Tip: Most drain pumps are not designed to pump hot water.

The unit has two pipes:

  • Entrance through which water is sucked in from a filled sewage pit.
  • Output, through it the liquid is discharged outside the site. Liquid must not enter the engine.
    This may damage the device. In this case, the pump must pump the effluent faster than their level can rise in the pit.

Tip: Pumps are brought to the sewer system through nozzles. Therefore, when installing a drainage pump, it is necessary to know the diameter of the sewer pipe with an accuracy of one millimeter.

The main advantage that a floatless drainage pump has is mobility. Equipment can be freely moved to any place where it is needed. Repairs in the event of a breakdown can be done quickly and easily.

Features of drainage pumps with floats

To protect pumping equipment, special float devices are used. The price of such devices is relatively small compared to the advantages they have.
There are two types of float switches:

  • Lightweight, used primarily in water supply and drainage systems.
  • Heavy, used for drainage, sewer, rainwater.

The float switch is a floating device in a plastic box.
Inside it are:

  • Electric switch. From it comes a cable with three wires of different colors: one wire is common and two are from the normally open and normally closed switch contacts.
  • A steel ball that closes or opens the circuit contacts when the float changes position.

When the float is at the bottom, the circuit is closed with a common wire and normally open. If the float is at the top, the contacts of the wires of the common and normally closed wires are closed.
The wire not currently used in the circuit must be insulated.

Tip: When purchasing a float, you should pay attention that the plastic box must be hermetically sealed, and the cable must be moisture resistant.

The cable outlet is sealed with a mechanical seal during manufacture. If it is necessary to remove mechanical stresses in the cable, a special device is used, which is included with the float.
The cavity where the cable enters is insulated and filled with polymer resin, which prevents moisture from penetrating inside. The material for the manufacture of the body has good heat resistance, and thermoplastic rubber is used for the cable sheath, which makes the float switch resistant to alcohols, harmful by the chemical composition of uric acid, liquid oils, gasoline and other substances.
There are no pores on the surface of the plastic case, which eliminates the possibility of all kinds of contaminants sticking to it. Sand, paper and other solids slide off freely without affecting the buoyancy of the float switch.

How to mount the device

The installation procedure for the float switches is as follows:

  • The amount of current consumed by the pump is checked. It must be less than the maximum allowable, which is indicated by the instruction manual for the float.

The easiest and fastest way is to install in a tank.
In this case, a float with a cable and a special weight that comes with the kit are used:

  • The weight is put on the cable and the size of the free play of the float is determined empirically.
  • The weight is fixed on the cable with a latch.
  • The cable itself is securely fastened outside the container.
  • The float switch is connected to the pump.

Tip: The installation of a float switch on the supply cable can only be carried out if there is no danger that the float switch can catch or hang inside the tank and there should be only one float switch in it.

When mounting several float switches in a tank, they must be fixed on a special rod. Its role is usually played by a piece of plastic pipe placed and securely fixed in a container. After that, floats are attached to the pipe.
For this they are:

  • Expose.
  • Regulate.
  • The rods are spaced along the length so that they cannot interfere with each other to properly perform their intended functions.
  • From the float switches, the cables going are fixed with clamps to the rod, as seen in the photo.

  • The number of float switches is selected depending on the number of pumps or on the number of protective devices, their types and the control panels used.
  • There are cases when it is necessary to use several rods for the reliable operation of these devices.

The quantity and where to mount float switches is determined individually at the place during installation or according to the project.

How does a float switch work

Several options for using float switches. The water supply system when filling and emptying the reservoir tank is in progress.
In this case:

  • The tank filling pump will turn off the float switch on the ascent when the tank being filled is full, and turn it on when sinking to the bottom if the tank is empty.
  • The device will turn on the water supply when it is on the surface, the tank will be full, and turn off the station when it sinks to the bottom, in which case the tank will be empty.
  • The device will give a command to close the valve or valve with a servo, when raised to the surface, the container will be filled and open the valve or latch when lowered to the bottom, the container will be empty.
  • The device will give a command to the dispatcher at the point or the operator, when raised to the surface, the tank is full, and it will give a signal about the lack of water, when lowered to the bottom, the tank will become empty.


Sewer system:

  • The device will turn on the fecal pump if it floats on the surface, the tank is full, and turns off the pump, when it sinks to the bottom, the tank will be empty.

Two pumps can be connected to one float: one pump will fill the tank if the float is in the lower position, at this time the second pump is not working, and in the upper position of the device the second pump is working, pumping out the tank, and the pump filling the tank, at this time work will not.
Such a scheme for using a float switch is not very effective, there may be interruptions in the delivery of liquid, for a while when filling the container. How a drainage pump with a float works is well shown in the video in this article.

Operation, repair and maintenance of float switches

Under all operating conditions, float switches operate for a long time without repair. If the device is used in the plumbing system or when draining water, it does not require periodic maintenance.
If the float switch will work in sewer pits, it is necessary to flush the float and the pump with a jet of water under pressure at least once a month, which will prevent the float from sticking or sticking to the drainage pump or pipe. If the contacts burn, moisture gets inside the float, or the cable insulation is damaged, the float switch cannot be repaired, but it needs to be replaced.