Foam bottle and machine-fed detergent are different systems
Two separate original diagrams show a lance-mounted foam bottle and a Plug n Clean machine bottle with a MIX lance; no hybrid plumbing is suggested.
Lance foam bottle
Its mixing path belongs to the removable accessory.
Machine bottle dock
The matched K4 Plug n Clean bottle sits opening down.
Required detergent mode
For that K4, use the Vario Power lance at MIX.
Find the actual detergent route first, then check that system’s bottle position, approved mixture and required low-pressure mode. Conceptual schematic, not a product image or scale drawing.
Identify the detergent route
A bottle fitted to the end of the lance is an accessory with its own mixing path. A bottle docked into the machine feeds a different system. Do not apply instructions for a suction tube or internal tank to a lance-mounted foam bottle that has neither.
Two examples show why this matters. Bosch UniversalAquatak 135 uses a foam-bottle accessory in its recommended cleaning method. Kärcher K4 Power Control Flex uses a Plug ‘n’ Clean bottle and the Vario Power lance in MIX mode. The same symptom, plain water, can therefore come from different setup errors.
Check the simple conditions before removing parts
Read the detergent label to confirm that it is approved for the washer and the surface, and mix only as directed. Thick product is not automatically “stronger”: the Bosch troubleshooting table identifies excessive viscosity as a reason for failed dispensing. Do not keep adding water arbitrarily; follow the product’s permitted dilution and the machine’s arrangement.
Check there is enough liquid for the actual pickup opening. Where a visible pickup tube is part of an approved foam bottle, confirm that it remains connected, unobstructed and reaches the liquid. Do not improvise a longer tube or pressurize the bottle to force pickup. Set the correct accessory and detergent mode before expecting suction.
Worked check: K4 Power Control Flex
For the matched Plug ‘n’ Clean system, stop operation before handling the bottle. Remove its lid and seat the appropriate bottle in the detergent connection with its opening down. Fit the Vario Power lance, then turn it until MIX is shown on the high-pressure gun. This machine adds detergent at low pressure; continuing to use a high-pressure cleaning setting is not a meaningful suction test.
Use the solution sparingly on a suitable surface and do not let it dry. If detergent is still absent, recheck the bottle seating and the indicated setting rather than opening the pump. A separate foam-cannon accessory may have different instructions even if it fits the same gun.
Rinse residue without dismantling the machine
Finish with the manufacturer’s clean-water flushing procedure. The K4 instructions specify removing and closing the bottle, storing it upright with the lid on, and flushing with clean water for about 30 seconds. Bosch’s fault table likewise calls for clean-water flushing when deposits obstruct the detergent path, then service if the fault remains.
Before detaching a bottle accessory or cleaning its user-removable parts, stop, unplug and release pressure according to the machine instructions. Rinse accessible parts only as allowed. Do not pour bleach, solvent or an improvised descaler into the pump, and do not mix cleaning chemicals to dissolve an unknown blockage.
Distinguish weak foam from no detergent
Thin foam is not proof that no solution is reaching the surface. Bottle concentration, accessory design and the selected product affect the result. Compare with the product and accessory instructions, not a promotional photograph of thick foam. Do not double concentration simply to make the appearance match.
If the correct liquid, dilution, seating, mode and permitted rinse do not restore dispensing, report the machine and accessory model and the exact product used. Stop if the bottle or connection leaks or is damaged. Internal detergent valves and tubing belong to service, not blind probing from the outside.