If the coffee machine has stopped pouring coffee in the usual stream, and instead of an invigorating drink, rare drops drip from the spout or produces a barely noticeable stream, this is a direct signal of a critical blockage of the brewing unit or a loss of pressure in the system. Most often, the problem lies in limescale deposits that have accumulated inside the boiler and pipes for years, or in worn-out seals that do not allow the required operating pressure of 9 bar to be created. Ignoring the “bad flow” symptom quickly leads to overheating of the heating element, since the water ceases to effectively remove heat, which can lead to costly hydraulic repairs.
The first thing the owner needs to do is check whether water flows at all, and whether access to the spout is blocked by a frozen coffee tablet. It often happens that the automation tries to push water through the compressed mass, but the resistance is too great, and the liquid looks for workarounds or simply stops. In some models, for example DeLonghi or Saeco, the pressure sensor can forcefully stop the cycle if it detects a flow anomaly, leaving you without your morning espresso.
Further diagnostics require consistent exclusion of causes: from a simple lack of water in the tank to complex depressurization of the hydraulic system. It is important to understand that weak pressure is not just an inconvenience, it is an indicator that the extraction is not going well, and you are not drinking coffee, but simply colored hot water without taste or cream. In this guide, we will go through in detail all the stages of restoring normal operation of your device.
The main causes of low pressure and their symptoms
A decrease in coffee machine performance is almost always associated with a breakdown in the hydraulic circuit. The most common reason is scale, which narrows the diameter of the internal channels. Even a microscopic layer of deposits on the walls of tubes with a diameter of several millimeters can reduce the throughput of the system several times. The water meets resistance, the pump works to the limit, but the output remains disastrous.
The second important factor is the condition of the brewing unit. If the mechanism is worn out or contaminated with coffee oils, it cannot form the correct tablet or, on the contrary, creates excess pressure, blocking the flow. It is also worth paying attention to pump (pump). Over time, its membrane loses elasticity, and it stops pumping water with the required force, even if it is electrically intact and hums when turned on.
⚠️ Attention: If, when you turn on the coffee preparation program, you hear a loud noise from the pump, but no water comes out or very little water comes out, stop working immediately. This can lead to pump burnout or gasket failure.
The third aspect is mechanical damage or displacement of internal elements. A crack in the tube, a slipped clamp or a burst siphon valve leads to depressurization. The system does not create the vacuum or pressure necessary to lift and pump fluid. In such cases, water may leak into the inner pan, creating the illusion that the pump is broken, although the problem lies in a simple leak.
Diagnostics and cleaning of the brewing unit
You should start troubleshooting from the most important unit - the brewing unit (brew group). This is where the magic of turning ground grain into drink happens, and where jams most often form. If you notice that coffee tablet after use, it remains too wet, crumbly or, conversely, excessively swollen and does not fold back into the waste compartment, which means the brewing process is disrupted.
To begin, remove the infuser according to the instructions for your model (usually Bosch, Siemens and Krups allow you to do this easily through the service door). Inspect the strainers carefully. If the holes in them are clogged with fine coffee dust or oily residue, water simply will not be able to pass through them at the required speed. Wash the filter under strong pressure of warm water using a soft brush.
If a visual inspection does not reveal obvious blockages, check the movement of the brewing mechanism pistons. They should move smoothly, without jerking. Dry running or jamming indicates the need to lubricate with food-grade silicone or replace worn cuffs. Also check to see if there are any coffee particles stuck in the rubber seals that seal the brew chamber.
☑️ Checklist for checking the brewing unit
Decalcification: combating scale in the hydraulic system
Even if you use filtered water, salt deposits inevitably accumulate in heating elements and narrow channels. Scale - the main enemy of any coffee equipment. It not only worsens the taste of the drink, but also physically blocks the path of liquid movement. When the machine does not pour coffee well, in 80% of cases it is to blame.
The decalcification (descaling) procedure should be carried out regularly, according to the manufacturer's recommendations. However, if the problem has already occurred, an enhanced mode will be required. Modern coffee machines Philips, Delonghi and others have a built-in cleaning program that can be activated through the menu. It is important to use only special liquid products, since citric acid or vinegar can damage the internal rubber seals and aluminum parts of the boiler.
⚠️ Attention: Never use acetic acid or aggressive household chemicals for decalcification. This can cause the pads to corrode and leave an unpleasant aftertaste in the coffee that cannot be removed.
If automatic flushing does not help, the blockage may be localized in the boiler itself or at the junction of the pipes. In such cases, craftsmen use the “decarbonization” method under pressure or disassemble the unit for mechanical cleaning. For prevention, it is recommended to do 2-3 flushing cycles with clean water after each cleaning to completely wash away the remaining dissolved salts.
Checking the pump and water supply system
When the mechanical part is clean and the pressure remains weak, suspicion falls on pump. This vibration or rotary pump produces a pressure of 9-15 bar. Over time (usually after 2-4 years of active use), the pump’s lifespan is exhausted. It may hum, but not develop the required pressure, or work with strong vibrations, creating the effect of a “pulsation” of the jet.
You can check the pump by disconnecting the water supply hose to the brewing unit (after disconnecting the machine from the network and relieving the pressure). When starting the water supply program, the stream should be powerful and even. If the water barely oozes out or comes out jerkily, the pump needs to be replaced. Also worth checking inlet valve**, which regulates the intake of water into the system. If it is clogged with debris from the tank or is faulty, the pump will run dry.
Another important element is flow meter. It not only counts the volume of water, but can also affect the operation of the system in some models. If its impeller is dirty and rotates with difficulty, this creates additional resistance to flow. Cleaning the flow meter will often restore the machine to its former performance.
Table: Diagnosis by symptoms
To simplify troubleshooting, use the table of symptoms and probable causes.
| Symptom | Probable Cause | Difficulty in eliminating |
|---|---|---|
| Coffee drips very slowly | Strainer or spout clogged | Low (cleaning) |
| Intermittent jet, with air | Air leak, low water level | Medium (leak test) |
| It hums but doesn't pour | Pump malfunction or severe blockage | High (assembly replacement) |
| Water goes into the pan | Depressurization, crack in the tube | High (hydraulic repair) |
| Weak pressure in all modes | Scale in the boiler, pump wear | Medium (decalcification/replacement) |
Settings for grinding degree and tablet density
Sometimes the problem lies not in a breakdown, but in incorrect settings. If you change the grain type or grind level, the hydraulics may no longer cope. Grind too fine (fine grind) creates a dense tablet that is difficult for water to pass through. The pressure increases and the flow decreases. As a result, the coffee may not come out at all or may come out in a black, bitter stream.
The grind control is usually located inside the bean hopper. You can twist it only when the millstones are rotating (during grinding), so as not to damage the mechanism. Try making the grind 1-2 notches coarser. This will reduce resistance and increase the flow rate. Also check the settings for water volume and coffee strength in the machine menu.
Critical: Don't ignore water quality. Using distilled water lacks the minerals needed for proper extraction, but water that is too hard will kill your car within six months. The golden mean is filtered water of medium hardness or bottled water for coffee.Prevention and proper care of the coffee machine
If the problem “coffee flows poorly” has not returned after a month, it is necessary to follow a prevention regimen. Clean the tray and drip tray daily. Remove and wash the brewing unit weekly (if the design allows). Once a month, clean the system of coffee oils with special tablets that dissolve fat that is invisible to the eye, but clogs the pores of the filters.
Do not leave water in the tank for a long time when you are not using the machine. Stagnant water “blooms”, and microorganisms, along with sediment, clog thin channels. Wipe the spout of the cappuccino maker and coffee dispenser immediately after use, until the remaining milk and coffee have dried tightly.
Regular maintenance extends the life of expensive equipment. If you notice that the machine begins to work noisier, heat up more, or change the nature of the jet, this is the first bell. A timely response will save you from buying a new device.
Why does the coffee machine hum but no coffee comes out?
A humming sound indicates pump operation. If there is no water, it means that it either is not sucked in (clogged at the inlet, empty tank), or cannot be pushed through (dead clogged in the boiler/group), or the pump has lost its performance and is simply circulating air. It is also possible that the solenoid valve may fail.
Can citric acid be used for cleaning?
Citric acid can be used only in extreme cases and in low concentrations, unless the manufacturer explicitly prohibits this in the instructions. However, modern descaling products contain corrosion inhibitors and surfactants, which are safer for rubber bands and aluminum. Citric acid can corrode old seals.
How often should the brewing unit be lubricated?
Lubrication is required as the old one dries or after each deep cleaning, but once every 3-6 months is usually sufficient. Use only food grade silicone. Conventional lubricant (litol, grease) is prohibited, as it is toxic and can give a coffee taste.
What should I do if water flows into the pan during cooking?
This is a sign of depressurization. Check whether the brewing unit is firmly inserted. If everything is in order with it, it means that the tube inside the housing has burst or the boiler gasket has broken. Requires disassembly and troubleshooting of hydraulics by a technician.
Does the type of coffee affect the pressure?
Yes, it does have an indirect effect. Oily, dark roasts clog filters more quickly and form deposits. Fresh coffee (less than a month old) produces a lot of CO2, which can create air pockets in the system that interfere with the flow of water. Let the coffee rest or use the pre-wetting mode.