There are three common sources, and they can be told apart without tools. The trap and its connections only leak when you run water. The supplies to the tap leak continuously, including overnight, because they are under pressure. The dishwasher hose or connection leaks during and just after a cycle.
Dry it, put a sheet of paper underneath, and watch for when it gets wet again. That answer tells you more than any photo.
In detail
The water appears when you run water and stops shortly after. Often it is a loosened plastic nut or a dried-out washer. It typically drips from a joint rather than from the pipe itself, and the water frequently smells of drains.
It gets wet even when nobody is using the kitchen. The supply pipes or the flexible hoses to the tap are under pressure around the clock, so a leak there never stops. This is the variant to take seriously fastest.
The water shows up during or just after a cycle and comes from behind the machine rather than from the pipe corner in the cupboard. Check the fill hose, the drain hose, and the point where the drain connects to the trap.
Put a bowl underneath, empty the cupboard and mop up so you can see whether more arrives. If it is really running: close the isolating valves under the sink, or the main stopcock if you cannot find them. Do not leave a damp chipboard cupboard shut — that is the damage that ends up costing more than the leak.
The open cupboard with the whole pipe arrangement visible, a close-up of the wet spot, and the paper or cloth after running water so it is clear whether it got wet. Say whether it gets wet when you run water, continuously, or only with the dishwasher.
What this page is not
This page describes what the symptom usually comes down to. It is not an assessment of your particular installation and it does not replace a professional who can see it. If water is running, you can smell gas, or anything involving electricity is in play: shut it off and call a professional now.
Other symptoms
Partly, and the part that is settled is the application key. An ECL Comfort 210 or 310 is an empty shell without one: the key carries the software layout, such as A266 for heating plus domestic hot water. Keys are not locked to a serial number and move freely between controllers of the same type.
Read the answer →Almost always air in the radiator. Hot water comes in and heats the lower part, but air has collected at the top where it cannot escape on its own, so the top stays cold. Bleeding the radiator is the first step and usually fixes it.
Read the answer →Condensation spreads evenly along a cold pipe, often as many small droplets on the underside, and gets worse when it is warm and humid indoors. A leak has a point: the damp is heaviest at a joint, a valve or a weld, and runs from there.
Read the answer →Not without knowing what it sits on. A valve can be the isolation for a single tap, for a whole flat, for a heating circuit, or for a system that cannot be left standing — and from the outside they look much alike. A closed heating or circulation circuit can cause frost damage or stagnant hot water long after you have forgotten you touched it.
Read the answer →The heating working while the hot water does not already says a good deal: the fault is usually in the part that only concerns hot water, not in the heat source. The most common are the cylinder or the heat exchanger, a broken or misadjusted mixing valve, or a stopped hot water circulation pump.
Read the answer →One thing to do next
Write a few lines and send a photo or a short video. You get a written first assessment of your own case — what it most likely is and what the next step is — for €9.99. A professional reads it, not just a machine.