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FAQ – Installation/Commissioning

On which water pipes is a Kärcher booster pump installed?

Kärcher booster pumps are designed to pump process water. They must not be connected to the drinking water supply.


What points must be borne in mind when installing a booster pump for house water supply?

The location must be dry, frost-proof and safe from flooding. Place the pump on a base or fit it to a wall bracket to protect it from ground moisture.

On the suction side, the maximum suction depth to the water reservoir is 8 metres. Pipe diameters should be ¾" – 1 ½", maximum pipe length 20 m. Fit connecting pieces carefully to prevent
air from being sucked in. If appropriate, fit filter.

Pressure side pipe diameters should be min. ½"–¾". In the case of booster pumps electronic (BPE models) fit a connecting hose for pressure compensation on the pump outlet (Kärcher accessory No. 6.997-417.0). Fit shut-off valves before and after the pump to aid servicing.


How far can the water source or reservoir (cistern, well) be from the pump location (height difference and distance)?

To keep transmission losses as low as possible, we recommend a pipe diameter of at least ¾" and a maximum length of 50 m.

A vacuum-proof suction hose, known as a spiral hose, must be used.

Suction depth (difference in altitude from water surface to pump connection) has a greater impact on pump performance than the hose diameter. The smaller the suction depth the better the pump performance. The maximum suction depth is 8 m.


What diameters and lengths of pipe must be used to install a booster pump?

As a matter of principle, pipes should be as wide as possible and as short as possible. The larger the diameter and the shorter the pipe, the lower the transmission resistance the pump has to overcome. This applies to both suction and pressure sides.

A diameter of ¾" is adequate for the suction side. If pipes are more than 10 m long, a 1” diameter pipe should be used. The maximum length should not exceed 50 m (pay attention to suction depth).

On the pressure side, we recommend that main pipes with a ¾" in diameter and secondary pipes
with a ½" diameter. For a pipe length of 50 metres, a ¾" diameter pipe should be used. If pipe lengths exceed 200 m performance is noticeably reduced due to transmission resistance. We recommend a diameter of at least 1".


What components are needed to connect a pump to a house water supply?

You need a wall bracket or base for the pump, along with fixing material and a sound-insulating mat as an underlay.

A suction pipe with a filter and check valve at the suction point and in front of the pump, along with a pump prefilter.

And on the pressure side, a connecting hose for pressure compensation and an shut-off valve.


Can the Kärcher connectors on Kärcher booster pumps and accessories be connected to other connecting pieces (suction and pressure connection) on the market?

The pump connectors have a standard G 1" thread. The pipes can be fitted to the booster pumps using commercially available adapters or connetor pieces.


Can hoses and pipes with metal screw connections be joined to the plastic screw necks of the pump connectors?

When fitting threaded metal connectors to plastic screw necks, the parts must be fitted and screwed carefully without excessive use of force. There is a risk that the metal connector will warp the plastic thread. If the thread is damaged the joint may not be watertight.


Is there a flexible hose system for Kärcher booster pumps that is an original Kärcher accessory?

Suction side; 0-5 m suction hose with connector (part No. 6.997-360) plus suction hose sold by the metre in various sizes with connecting accessories (see Kärcher catalogue).

NB: a suction-side hose connection must be vacuum-proof, so Kärcher makes spiral suction hoses.

Pressure side: connecting hose for pressure compensation part No. 6.997-417.0


Is it important to use a prefilter?

To ensure problem-free operation when water is drawn off, prefilters are used. Otherwise, given the small diameters of some water taps, washing machine pipes, WC cistern valves, sprinkler and spray nozzles, blockages may occur. Kärcher booster pumps have an integrated prefilter with a 500µm mesh gauge as standard. If the water is especially dirty or sandy, we recommend using an additional pump prefilter (Kärcher accessory number, up to 3,000 l/hour 6.997-343 or up to 6000 l/h 6.997-344.0). This has a 250µm mesh gauge.



Where must a check valve be installed?

A check valve is installed on the suction side. It opens in the direction of flow.


Is it possible to connect quick couplings to the suction and pressure sides of Kärcher pumps?

Quick couplings are critical on the suction side. In some systems, air leaks can arise in suction operation, and water can only be drawn in to a limited extent (e.g. Geka Bayonet couplings).

Quick couplings can be used on the pressure side as long as they are pressure-tight and designed for continuous duty.


How do I start up Kärcher booster pumps?

Ensure that a reservoir of water is available (e.g. a filled cistern) and that water will be replenished as it is used.

The suction and pressure pipe system, along with supplementary accessories, must have been installed.

On initial start-up you must fill the pump with water (c. 2.5 litres).

The pressure tank of a BPP booster pump must be filled with air pressure at 1.8-2.0 bar.

On the pressure side, the system must first be opened on the highest water outlet, so that water can be pumped to prime the system.

The pump starts up promptly when the plug is plugged into the electrical socket. It must pump until water is being pumped evenly, then the pressure-side system must be closed (by turning off the water tap at the highest point).

The pump then builds up pressure and finally shuts down automatically.


Are there ways of reducing the pump operating noise?

Fixed pipes should not be connected rigidly to the pump to ensure that operating noise is not transmitted. For decoupling, use only flexible hosepipes.

For the suction side: 0.5 m suction hose with threaded neck (part No. 6.997-360), and suction hose sold by the metre in various sizes with connecting accessories (see Kärcher catalogue).

The connecting hose for pressure compensation, that is connected on the pressure side reduces pressure surge in the piping system (Kärcher accessory, part No. 6.997-417.0).

A rubber mat can be laid under the pump (similarly to those used with washing machines) to absorb vibration The rubber mat has a sound-insulating effect.


What delayed shutdown period should be set on the booster pumps electronic (BPE)?

As a general rule, the delayed shutdown period should be set so that the pump continues running for as short a time as possible after it has stopped drawing water (water tap or valve turned off).

However, if water is drawn off at frequent intervals (e.g. for watering plants and changing from bed to bed), a longer delayed shutdown period must be set. This prevents the pump from being activated each time the valve is opened or closed. Reducing the number of times the pump switches on and off helps to preserve it. Find the optimal setting by gradually increasing the delayed shutdown time.


The pressure indicator on the Kärcher electronic booster pump (BPE) shows a different pressure from that which I can measure at the water tap? Why?

The length and diameter of pipes leads to resistance that the pump must overcome. Therefore, the pressure at the end of the pipe (water tap) is lower than at the pump.

To reduce loss of performance as a result of transmission resistance, for longer tracts or pipes running to different floors we recommend using main pipes with a minimum diameter of ¾" and a minimum diameter of ½" for secondary pipe runs to take-off points.

For suction pipes min. ¾", recommendation 1" or 11/4" pipe diameter.


What maintenance do booster pumps require (BPE / BPP)?

Kärcher booster pumps electronic and booster pumps with pressure tank are maintenance-free. We recommend checking the pipe connections at least once year to ensure there is no loosening or leakage.

The filter of the pump prefilter should also be checked regularly for soiling and cleaned of any visible dirt.

In the case of the BPP booster pumps we recommend checking the pressure of the air in the storage tank at least once a year (target value 1.8–2.0 bar).


Is it possible to change the pressure accumulator diaphragm in a booster pump with pressure tank?

Yes, it is possible to change the pressure accumulator. Please have this work carried out by a Kärcher-approved craftsman.


I want to swap the integrated storage tank on a booster pump with pressure tank (BPP) for an external expansion tank. Is that possible?

An external expansion tank or pressurised tank can be installed in addition to the integrated storage tank or, if appropriately dimensioned, can replace it entirely.