Fill the tank when the pump stops

This is how you vent your domestic waterworks - what to do if air enters the domestic waterworks

your Domestic waterworks is wonderfully suitable for regulating water pressure if your pipe system does not reach enough water pressure for the customers on the upper floors. In addition, a waterworks can be used very well for watering the garden from rainwater cisterns or for supplying service water with rainwater. In all usage variants, it is important never to forget to bleed the air.

A domestic waterworks is basically one Water pump with pressure tank. The domestic waterworks supplies the consumers (depending on the use: taps, toilet cisterns, washing machine, garden hose, etc.) with sufficient water pressure via a suction hose, which should be equipped with a non-return valve with filter basket. If water is withdrawn from a consumer, the pressure in the pressure vessel drops and the pump of the domestic waterworks starts again when the switch-on pressure is reached. As soon as the cut-off pressure is reached in the pressure tank, the domestic water system switches off automatically. You must have your Waterworks if necessary vent. In addition, the pressure in the pressure vessel must be checked regularly. In the event of a defect, the membrane in the pressure vessel must be replaced with a new one.

So that the domestic waterworks can do its job properly, it must not draw in any air or run dry. This can happen if the check valve is defective and can therefore no longer close properly. On the one hand, this can happen if the filter on the non-return valve is defective and foreign bodies get into the non-return valve or if rust has formed in the non-return valve itself. If the non-return valve can no longer close properly, the suction hose will run empty and the domestic waterworks will no longer be able to prime properly. Sometimes it is enough to clean the check valve thoroughly. If this does not help, it is essential to replace it with a new check valve. You will then have to vent your domestic waterworks before you can operate it again.

In general, it is advisable to never use a domestic waterworks without it Dry run protection to operate. The dry run protection ensures that the domestic water system never works without water - i.e. dry. Without dry-running protection, the domestic waterworks pump would run until it stopped working due to overheating. It is rarely repairable and reusable afterwards.

In the winter half-year it must be ensured that the domestic waterworks housed frost-free or has been completely emptied so that no residual water can freeze. It must then be vented again for commissioning in spring. In this case - before commissioning - all components and accessories of the domestic waterworks must be checked for fault-free function and replaced if necessary.

Modern domestic waterworks in particular usually have a water pump that actually no longer needs to be vented. However, with self-built and older domestic waterworks, there is definitely a need to vent this. There may also be another problem with modern domestic waterworks. In the following, we will show you how to bleed a domestic water system, but also what could otherwise be the cause of a malfunction.

Used pumps in domestic waterworks

More and more domestic waterworks are being used in private households and gardens. This also increases the number of malfunctions. Air in the system is often the reason for this, but the problem cannot always be solved by venting. To do this, the various pumps that can be used in the domestic waterworks must first be considered:

  • Suction pumps
  • Centrifugal pumps
  • Jet pumps (further development of the centrifugal pump)
  • The suction pump in the domestic waterworks

As already indicated, the suction pump can suck in the water itself. However, only within the range of negative pressure, i.e. between our prevailing atmospheric pressure and a pressure of zero) below that, the vacuum begins). We explain the principle in more detail under “the domestic waterworks draws air”.

It is not always possible to ventilate

However, if the suction pump does not work, the suction path may be disturbed. The foot valve may no longer be tight, so that the water flows back into the well or the cistern while it is not being pumped. The sieve located there could also be clogged. But an upstream filter could also be tight. Then there is the possibility that there is a leak somewhere from the inlet to the pump and air is drawn in.

New pumps usually bleed themselves

With newer suction pumps it should also be taken into account that they mostly vent themselves. Pumps that can still be vented can be identified by a corresponding screw, the vent screw. The pump is switched on, the vent screw then remains open until water comes in. As already mentioned, it is possible that the riser is no longer filled with water.

Venting a domestic waterworks

Then this must first be refilled if the pump cannot suck in water on its own. With these older pumps, it is usually sufficient if water is topped up precisely through this vent opening.

Submersible and jet pumps

The centrifugal pump is a pump that must be immersed in the water to be pumped. If this pump no longer delivers, there must be another cause. The further development, the jet pump, on the other hand, is a self-venting centrifugal pump. If this no longer works, there is also a major defect.

Such modern pumps are often equipped with a microswitch that measures the pressure. These microswitches can also break. Then the pump appears like a domestic waterworks that only needs to be vented. If false air is sucked in, it often collects around the conveyor wheel, creating cavitation. This condition must be remedied quickly, as it can lead to greater damage to the domestic water system.

An important prerequisite is that the domestic water system is cool and frost-proof. As a result, the installation options for the domestic waterworks are usually very limited. This then often results in the domestic waterworks drawing in air.

The most common reason for drawn air: exceeded maximum lengths

Because an important point that must be taken into account is the maximum delivery head of the domestic waterworks. A distinction must be made between the delivery from the depth to the pump and the delivery head after the pump. The "sucking in" of the water is linked to the physical laws of the negative pressure.

Suction pumps work with negative pressure

Negative pressure is the range between our ambient pressure (atmospheric overpressure) and zero. Vacuum begins below this. This range of negative pressure can also be transferred to the water pressure. This pressure range corresponds roughly to a 10 m high water column. Now, however, no pump can deliver this full 10 m column of water (with the exception of submersible pumps).

The efficiency of the pump is also crucial

Because every pump also has one Efficiency. Based on the laws of physics, this efficiency must always be less than 100. The efficiency of really good pumps is sufficient to suck in a water column of around 8 m. In addition, cavitation occurs on the pump wheel. So air collects around the pump wheel, the pump draws air.

The construction of the domestic waterworks in order to identify all weak points

But even if all the requirements are met, air is always drawn. But first the typical structure of a domestic waterworks conveyor system:

  • Delivery line with foot valve
  • Filters (e.g. sand filters or cartridge filters)
  • Domestic waterworks
  • Connection of the distribution line
  • Foot filters and filters

The foot valve ensures that the water stays in the riser. Otherwise you may have to vent the domestic waterworks. There can also be a leak in a pipe connection. In addition, there is often a sieve on the foot valve to keep coarse dirt out of the power system.

If this is partially blocked, the delivery rate cannot be fully used. All of these points can also cause the domestic waterworks to draw air. The same applies to an upstream filter. This must also be vented. Here we show you how to vent a sand filter.

Cavitation in the pump of the domestic waterworks

All of these possibilities can lead to cavitation on the pump wheel. In other words: the pump runs dry. However, water pumps from many domestic waterworks are not designed for this. The water is needed to lubricate as well as to cool the pump. However, because such an incident can occur again and again that the domestic waterworks draws air, we generally recommend using a water pump with dry-run protection.

Finally, we will give you a few instructions that I can generally apply to all domestic waterworks. Nevertheless, refer to the manual for your domestic waterworks.

What you need to do this

  • Instructions for use for your domestic waterworks
  • matching open-end wrenches
  • a vessel for filling
  • a vessel to catch water

This is how you vent your domestic waterworks

If the suction hose is still empty (during initial installation or when restarting in spring), fill the suction hose next and reconnect it to the domestic waterworks.

Now open the vent screw (s) so that you can vent your domestic water system. You will find a precise explanation of where these are in the instructions for use for your domestic waterworks. Depending on the manufacturer and device type, you will find the screw (s) for venting in different places.

In the winter months, it must be ensured that the domestic water system is housed frost-free or has been completely emptied so that no residual water can freeze. Now all air has been displaced from the pump by the water. The venting of the domestic waterworks is completed when the vent screw is closed.

If you bleed your domestic waterworks in good time and always keep an eye on possible sources of error, you will be able to enjoy your water for a long time Domestic waterworks to have.

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