Why touchless soap dispensers leak or do not respond to motion

We are still preparing products.

But you can look at other categories.

Why a touchless faucet leaks or doesn't respond to motion – a complete diagnostic and repair guide

A touchless faucet is a reliable helper in every bathroom or toilet – until it stops behaving as expected. Either water leaks when it shouldn't, or on the contrary, it doesn't respond to hand movement, even though you're holding your hands directly in front of the sensor. Both situations are frustrating, but they usually have a very specific technical cause that can be diagnosed and eliminated without you having to immediately call a plumber or buy a new faucet.

In this article, we systematically cover both problems – unwanted leakage and a non-responsive sensor – from the basics up. We'll explain the physical principles on which the infrared sensor operates, explain where errors most commonly occur in practice, and give you a step-by-step guide on how to locate and fix the problem yourself. Most causes don't require any tools or specialized knowledge – it's enough to know where to look.

How a touchless faucet actually works – the basis for understanding faults

Before we start solving specific faults, it's important to understand the operating principle. A touchless faucet works on the basis of an active infrared sensor. The transmitter (emitter) emits a narrow beam of infrared light with a wavelength typically around 850–940 nm – that is, outside the visible spectrum. The receiver (detector) monitors whether this beam is reflected from any object within range.

When you bring your hands into the detection zone, the beam reflects back to the receiver. The electronic control unit evaluates this signal, opens the solenoid valve, and water starts flowing. When you pull your hands away, the reflected signal disappears, and the control unit closes the valve after a set time (typically 0.5–3 seconds).

This is a key point: the sensor does not react to touch or heat, but to light reflection. Therefore, it can be affected by things you wouldn't expect from a regular light sensor – reflective surfaces, direct sunlight, condensation on the lens, or dirt that changes reflectivity. When you understand this, most faults immediately make logical sense.

Faucet leaks constantly – causes and diagnosis

Unintended water leakage is a more serious problem from an energy and economic perspective. A faucet that leaks continuously can release dozens of liters of water in an hour. The causes can be divided into several groups.

1. The sensor "sees" something in the detection zone – false detection

This is by far the most common cause of unintended leakage. The sensor detects a reflected IR beam from an object that shouldn't be there. In practice, I've encountered this in the following situations:

Shiny surface directly opposite the sensor: A faucet mounted in front of a mirror or on a shiny tile without sufficient distance. The beam reflects directly off the mirror back to the receiver – the sensor thinks a hand is there, and the valve remains open.
Object in the sink or under the spout: Soap, a sponge, a bottle, a plastic cup – anything placed within the sensor's range will cause continuous detection. Particularly tricky is when it's a small object near the bottom of the sink that isn't immediately visible.
Condensation of water vapor: In the bathroom after a shower, the air is full of water vapor. In some older sensor types with lower selectivity, dense vapor can scatter the beam, which the sensor interprets as movement detection. More modern sensors have this issue addressed with digital signal filtering.
Direct sunlight or strong artificial light: The infrared component of sunlight can saturate the receiver. This is especially problematic in the early hours when the sun shines directly into the bathroom. A solution is to change the faucet's orientation or shade the window.
Another IR source in the room: Dimmable LED lights, some infrared heaters, or even televisions in the hallway can send an IR signal to the faucet at the same wavelength. This is rare, but it does happen.

The diagnostic procedure for unintended leakage is simple: cover the sensor with an opaque tape or your hand. If the leakage stops, the problem is definitely with the sensor (false detection or electronic failure). If the water continues to flow even with the sensor covered, the problem is mechanical – the solenoid valve is not closing properly, or it is jammed with dirt.

2. Solenoid valve failure – mechanical problem

The solenoid valve is the heart of the entire touchless faucet. It consists of a coil, a plunger, and a sealing ring. When the electronics sends a signal to close, the coil disengages and the spring pushes the plunger against the seat. If the sealing ring of the valve seat has degraded, hardened due to limescale, or has been damaged by mechanical impurities (sand, rust from pipes), the valve will not close completely and water will continue to flow.

This is a common issue in bathrooms with hard water (over 15 °dH) after 3–5 years of operation. Limescale accumulates on the valve seat and the plunger, gradually worsening the sealing contact. The solution is to disassemble and thoroughly clean the valve in vinegar or a special descaling agent. In more severe cases, it is necessary to replace the sealing ring or the entire valve assembly.

3. Incorrect sensor sensitivity setting

Many touchless faucets from Donner allow you to adjust the sensor sensitivity – that is, the maximum detection range. If the sensitivity is set too high, the sensor detects movement even when you just pass by the sink, or reacts to a distant wall in a small toilet. In most models, sensitivity is adjusted using a small trimmer (potentiometer) on the control board under the faucet, or in the control unit program. The adjustment procedure is always found in the manual for the specific faucet. If you have lost the manual, try turning the sensitivity to the minimum and observe whether the faucet's behavior improves.

Faucet does not react to movement – where to look for the problem

The second scenario is the opposite: you bring your hands close, wait for water, but nothing happens. Or the faucet reacts only sometimes, irregularly, with a delay. This problem has even more possible causes.

1. Weak or depleted power supply

This is the number one cause in 60–70 % of sensor malfunction cases, as confirmed by everyday customer experience. Touchless faucets powered by batteries (typically 4× or 6× AA/C alkaline batteries) have a power limit: most solenoids require at least 4.5–5.5 V for reliable valve opening. When the voltage drops below this level, the sensor still lights up and reacts, but the valve does not have enough energy to open. The result looks exactly like a sensor failure, although the sensor is working properly – the valve just has nothing to open.

Practical test: measure the voltage of the batteries under load (i.e., when you try to activate the faucet). Alkaline AA batteries have a nominal voltage of 1.5 V each, so a 4-cell pack is 6 V. If you measure less than 5.5 V at rest and the voltage drops below 5 V when trying to activate the faucet, the batteries are too weak and need to be replaced.

We discuss this topic in more detail in the article Power supply for touchless faucets – batteries, mains or solar panel, where you will also find a comparison of the lifespan of different battery types.

2. Dirty sensor lens

The sensor lens is a small plastic window with a diameter of 5–10 mm, through which the IR beam passes. In the bathroom, this window is exposed to water droplets, soap scum, hand oils, dust, and limescale. If a non-transparent layer of deposits forms on the lens, the intensity of the emitted and received beam may drop by as much as 80–90 %. The sensor either stops working completely or the range shortens so much that the faucet only reacts when the lens is touched.

Diagnosis: look at the sensor lens. If you see white deposits (limescale), oily film, or cloudiness, this is the cause. The solution is simple: gently wipe the lens with a soft damp cloth. In the case of limescale, soak it in a mild citric acid solution (1 teaspoon per 200 ml of water). Never use abrasive agents or rough sponges – you may scratch the lens and make the problem worse. Cleaning the sensor is discussed in detail in the article Cleaning and maintenance of touchless faucets – how to extend the life of the sensor.

3. Improper installation or sensor position

The sensor has an optimal angle of detection. Most manufacturers design the sensor to detect hands directly under the outlet, typically at a distance of 10–20 cm. If the faucet is mounted too high (for example, on basins over 10 cm or with high outlets), or if the sensor axis is tilted more than 15–20 degrees from the vertical, the detection zone may be misaligned. You insert your hands under the water, but the sensor does not see them because it is looking elsewhere.

This often happens with DIY installations, where the mounting angle was adjusted for aesthetics rather than technical specifications. More about proper installation can be found in the article Step-by-step installation of Donner touchless faucet. In general: the sensor axis should point slightly downward (5–15° from the horizontal) and illuminate the area where your hands will be placed during normal handwashing.

4. Control electronics failure

The electronic control board is relatively robust, but not indestructible. The most common causes of its failure are:

Water condensation: In a bathroom with high humidity, moisture can penetrate into the electronic housing. Corrosion micropores on the printed circuit board gradually undermine the reliability of the circuits.
Overvoltage: In mains-powered faucets, a short voltage spike (from a storm, or from switching appliances) can damage the input protection or the processor.
Physical damage: A fall during installation, an impact during repair, or over-tightening of the screws on the electronics cover.
Capacitor aging: Electrolytic capacitors on the board have a typical lifespan of 5–10 years. After this period, intermittent faults may appear – the faucet works sometimes, sometimes not.

Repairing electronic faults is quite difficult without electronic knowledge. In practice, it is more economical to replace the control board (if available as a spare part) or the entire faucet.

5. Insufficient sensor range – incorrect distance

Each sensor has a designed maximum range. Most touchless faucets for home use have a range of 15–25 cm. If you try to activate the faucet from a greater distance, or if you have a deep sink and your hands are far from the sensor, the faucet may not react. This is not a fault – it is a design feature. We discuss this topic in more detail in the article What sensor range do I need for a sink or countertop.

Hand dryer is dripping intermittently – the most basic pitfall

A special chapter is intermittent dripping: the dryer is working, then it spontaneously turns on or off without any visible reason. This is the most difficult category to diagnose, because the cause can appear and disappear alternately.

Vibrations and air movement

Strong wind in the bathroom, ceiling fan lights or airflow from ventilation can move curtains, towels or other objects around the dryer. If these objects move cyclically into and out of the detection zone, the dryer reacts to their movement and water drips intermittently. A simple test: close all windows and turn off the ventilation, observe whether the problem disappears.

Unstable power supply

Hand dryers that are approaching the end of their life do not have a constant voltage – the voltage fluctuates depending on temperature and load. In the morning after a cold night, the voltage may drop below the minimum and the dryer does not respond, while during the day with temperature stabilization it works normally. This symptom is a classic sign of dryers at the end of their life – a simple replacement with new dryers immediately solves the problem.

Electromagnetic interference

In households with cheap electrical installations or with old distribution boards, short voltage spikes can occur when large appliances are turned on – washing machines, dishwashers, water heaters. These spikes can activate the control electronics of the dryer for a fraction of a second. A solution is to install a circuit breaker with surge protection or to filter the power supply through a small capacitor (for mains-powered models this must be done by a certified electrician).

Contactless hand dryer still not working after battery replacement

A classic trap: you replace the batteries, but the problem persists. Why? Here are the most common reasons:

Incorrect battery orientation in the housing: Sounds trivial, but even experienced people occasionally forget to check the polarity. If even one battery is reversed, the power circuit may work partially or not at all.
Poor quality batteries: Cheap no-name alkaline batteries can have significantly lower capacity and especially higher internal resistance. Under high current load (a solenoid when opening requires a peak current of 200–400 mA), the voltage immediately drops below the minimum. Always use branded batteries (Duracell, Energizer, Varta) or even better lithium-alkaline batteries, which have lower internal resistance and longer life.
Corrosive battery housing: If previous batteries leaked (which often happens with cheap types), the corrosive electrolyte may have damaged the contacts in the housing. Contacts need to be mechanically cleaned with fine sandpaper or contact spray.
Reset procedure: Some models of control units enter a calibration mode after a long period without power or after battery replacement. In this mode, they do not respond to movement until they calibrate – this process typically takes 10–30 seconds. Simply wait until the LED indicator stops blinking.

When water flows for too short or too long

Not always is the problem that the dryer does not work at all. Sometimes it works, but incorrectly – the water stops too soon (for example, after 1 second instead of 3 seconds) or flows for too long after removing your hands. Both of these states are the result of incorrect timer settings in the control unit.

The flow time after removing your hands (also known as delay time or afterflow time) is usually adjustable. In Donner dryers, this parameter is accessible either via a trimmer on the board or via a DIP switch. A typical range is 0.5–10 seconds. For regular hand washing, an optimal value is 2–4 seconds – enough to rinse off soap residue, but not so long that water unnecessarily flows after you have left.

If the dryer stops the water too soon, it may also be due to a late opening of the valve (power at the minimum limit, the solenoid does not fully open and quickly closes) – which again indicates a power supply problem.

Typical scenarios from practice – what actually happens

Case 1 – Restaurant, public restroom: After 4 years of operation, the dryer started dripping continuously. The customer was convinced that the entire dryer had to be replaced. After inspection, it turned out that the sensor lens was covered with a thick layer of limescale, so the sensor could not distinguish when hands were present and when they were not – it was operating only on background noise, which it interpreted as constant detection. After thorough descaling and sensitivity calibration, the dryer has been working without problems ever since.

Case 2 – Family home, bathroom: The dryer stopped working completely after battery replacement. The customer tried three different sets of batteries, but the problem persisted. It turned out that the previous batteries had leaked and the electrolyte had damaged one of the contacts in the housing. The contact looked visually fine, but when measured it had a resistance of 15 Ω instead of zero – enough to cause the voltage to drop below the minimum for the solenoid under load. After cleaning the contact with sandpaper, the dryer immediately came back to life.

Case 3 – Small WC, window facing west: The faucet started dripping on its own around 16:00–17:00 every day and stopped after an hour. The customer suspected the electronics. The cause was prosaic: the setting sun shone directly through the small window onto the sensor of the faucet. A simple solution: a curtain on the window completely eliminated the problem.

Case 4 – Office building, movable paper towel dispenser stand: The faucet activated sporadically, even though no one was standing by the sink. The paper towel dispenser was placed exactly within the sensor's range, about 18 cm from the lens. When the dispenser wobbled due to air flow or when someone took a towel, the faucet's sensor interpreted it as a hand movement. Moving the dispenser 30 cm to the side solved the problem.

Preventive maintenance – how to avoid malfunctions

Most malfunctions of touchless faucets can be prevented with regular, low-effort maintenance:

Clean the sensor lens once every 2–4 weeks – a soft cloth is enough, or once a month a solution of citric acid. In areas with hard water (Bratislava, Nitra, Trnava), cleaning every 2 weeks is recommended.
Change batteries preventively – don't wait until the faucet stops working. Alkaline AA batteries in a typical home WC last about 1–2 years. Set a reminder in your calendar.
Check the sensor's surroundings during every bathroom rearrangement – every new object, mirror, or light can interfere with the detection zone.
Check the solenoid once a year – when draining aerators, also check the valve to ensure it closes properly.
Check the faucet housing for tightness – if the batteries are damp or there is oxidation on the contacts, replace them even if they are not yet depleted.

A more detailed maintenance procedure can be found in the article Cleaning and maintenance of touchless faucets – how to extend the sensor's lifespan.

When to call a professional or replace the faucet

Not every malfunction is reasonable to fix yourself. Professional service or faucet replacement is appropriate in these situations:

Control electronics malfunction (the board is physically damaged, corroded, or the sensor displays error LED codes not described in the manual).
The solenoid valve is mechanically damaged or leaks even after replacing the seals.
The faucet is out of warranty and spare parts are not available – in this case, replacement is more economical than repair.
A malfunction occurs on a model powered by the grid and you suspect a problem with the power transformer or input electronics – these tasks belong to an electrician.

If you are considering a new faucet, the article How to choose a touchless faucet for the bathroom – what to pay attention to and the comparison of types in the article Touchless vs. classic faucets – is the transition to touchless worth it will help you with the selection. You can find a range of touchless faucets directly in the category Donner touchless faucets.

Most frequently asked questions (FAQ)

Why does my touchless faucet drip only at night, but not during the day?

The most common cause is the temperature effect on batteries. In the colder night, the internal voltage of alkaline batteries drops, which can cause instability in the control electronics – the sensor shows false detections or the valve does not close properly. Another possibility is that in the night, there is a different infrared source in the bathroom (e.g., a motion detector for lighting) that interferes with the faucet's sensor. Replace the batteries with new branded ones and observe whether the condition improves.

The faucet stopped reacting immediately after installation – what am I doing wrong?

The first thing to check: the calibration time after powering on. Most models perform a 15–30 second initialization after the first battery connection, during which they do not react. Also check the polarity of the batteries and the voltage (min. 5.5 V for new batteries). Another cause may be an incorrectly set sensor sensitivity – if the trimmer is at minimum, the sensor has a range of only 1–2 cm. Try slightly increasing the sensitivity.

Can I use rechargeable NiMH batteries instead of alkaline ones?

Theoretically yes, but in practice it is problematic. Rechargeable NiMH batteries have a nominal voltage of 1.2 V per unit instead of 1.5 V for alkaline. With a 4-piece set, this is 4.8 V instead of 6 V – and many solenoids have a minimum threshold exactly around 5 V. The result is unreliable valve opening, shorter sensor range, and the symptom "batteries are weak" appears sooner. Lithium-alkaline batteries (e.g., Energizer Ultimate Lithium) are the best choice – they have a voltage of 1.5 V, significantly lower internal resistance, and last 3–5 times longer than standard alkaline batteries.

The sensor reacts to my hands, but the water does not flow – what is happening?

This typically indicates a problem in another part of the system than the sensor. The most common cause is weak power – the sensor has enough energy for detection (low current), but not for opening the solenoid valve (high current). Another possibility is a malfunction of the solenoid valve itself: the coil is burned out, or the valve is mechanically stuck (e.g., sand or dirt in the seat). Try a replacement set of batteries, and if the problem persists, the valve will need to be checked.

Do I need to disconnect the water supply before repairing the sensor?

It depends on the type of repair. For cleaning the sensor lens or replacing the power batteries, it is not necessary to close the water supply – these tasks are purely external. However, if you are going to replace the solenoid valve, seals, or control board, always first close the hot and cold water supply under the sink and drain the existing water in the pipes (open the supply briefly after closing the valves). For grid-powered models, always disconnect the power cable before any work on the faucet.

The faucet blinks LED but does not work – what does it mean?

LED indicators on touchless faucets communicate the system status using blinking codes. One slow blink every 2 seconds typically means low battery level (needs to be replaced). Rapid blinking (3–5 times per second) may indicate detection of an object in the sensor zone or sensor error. Some models blink during calibration after battery replacement. The exact meaning of the codes can be found in the attached manual – each manufacturer has its own coding.

Conclusion – most malfunctions can be solved without a technician

Touchless faucets are actually quite robust devices. Most malfunctions that customers encounter in practice – unintended dripping, non-responsive sensor, intermittent operation – have simple causes and solutions that you can handle yourself in a few minutes. The key is a systematic approach: first eliminate the power supply, then check the sensor lens, then examine the faucet's surroundings, and only then consider mechanical or electronic malfunctions.

If you are unsure about choosing the right model or solving a specific malfunction, the category Donner touchless faucets contains models with various types of power supply, sensor range, and functions – you will find a solution for every bathroom and commercial space there. You can also find more useful information in the articles Common malfunctions of touchless faucets and their solutions, Power supply for touchless faucets – batteries, grid or solar panel, and Common questions about Donner touchless faucets.

Do you have a question about this topic?

Not sure or dealing with a specific situation in your home? Write to us – we are happy to help.