Facebook pixel
new boiler

Get a new boiler

Fixed price boilers, next day

See boiler prices
new air conditioning

Air Conditioning

Get a quote
new heat pump

Heat Pumps

Coming soon

new ev charger

EV Chargers

Get a quote
boiler servicing

Boiler Servicing

Get a quote

Last updated: 13th June, 2024


No Water Coming Out Of Hot Tap (Combi Boiler)

No Water Coming Out Of Hot Tap (Combi Boiler)

Key takeaways

  • A malfunctioning combi boiler can lead to the absence of hot water from taps.
  • Systematic troubleshooting can identify issues like faulty components or blocked pipes.
  • Persistent problems may necessitate professional repair or consideration of boiler replacement.

Addressing the lack of hot water from a tap usually starts with understanding how a combi boiler operates.

Experiencing no water coming out of the hot tap can be an inconvenient and baffling issue for homeowners. The combi boiler, which provides both heating and hot water without the need for a separate water tank, is at the heart of many modern domestic heating systems.

When a hot tap is turned on but yields no water, it necessitates immediate attention, as the problem can stem from numerous causes, ranging from the simple to the complex.

Addressing the lack of hot water from a tap usually starts with understanding how a combi boiler operates. The system heats water on-demand, meaning it does not require a storage cylinder.

However, intricate mechanisms within the boiler may lead to unexpected interruptions in service. Diagnosing the issue requires a systematic approach, checking potential causes such as malfunctioning diverter valves, blocked pipes, or even settings inadvertently adjusted.

Understanding Your Combi Boiler

Combi boilers, compact in size, serve as efficient dual-purpose units. They cater to both hot water and central heating needs without the requirement of a separate water tank, proving their worth in space-saving within homes.

Components and Operation

Combi boilers are composed of different key elements, each integral to the unit’s smooth functioning. At the heart of the system lies the gas burner which heats water on demand.

This occurs through an exchanger, transferring heat to water that circulates through the taps and radiators. Crucial to this process is the thermostat which monitors and controls the temperature, ensuring comfort and efficiency.

  • Main Components:

    • Burner

    • Heat Exchanger

    • Thermostat

The operation of these boilers is straightforward: a signal is sent from the tap or heating request to the boiler, igniting the burner which starts the heating cycle. Once heated, water is ushered to its destination—either towards radiators for heating or out of taps for hot water.

Common Boiler Issues

Several problems can plague a combi boiler, causing inconvenience to households. A typical issue is a faulty thermostat, which could misread temperatures and disrupt boiler function.

Additionally, boiler pressure stands as a frequent concern; too low or too high can signal underlying issues. Users should also be aware of error codes displayed on the boiler, as these codes direct to specific malfunctions, guidance for which is usually found in the boiler manual.

  • Frequent Problems:

    • Faulty thermostat

    • Incorrect boiler pressure

    • Boiler error codes

Boiler Pressure and Its Effects

Maintaining correct boiler pressure is essential for the combi boiler to operate effectively. A visible pressure gauge on the boiler should indicate a range normally between 1 to 2 bar. If the needle dips below this range, it is an indication of low water pressure, symptomatic of leaks or a need to repressurise the system.

Conversely, high pressure could suggest an excess of water within the system or that the pressure relief valve needs attention. In both scenarios, adjustments can be usually performed by referring to the boiler manual, or professional assistance may be required.

  • Boiler Pressure Guide:

    • Optimal Range: 1-2 bar

    • Low Pressure: Below 1 bar

    • High Pressure: Above 2 bar

Diagnosing No Hot Water Issues

When a combi boiler fails to deliver hot water, the underlying issues often include problems with water pressure, diverter valves, airlocks, or leaks and blockages. A methodical approach is necessary to identify and remedy the cause.

Investigating Water Pressure

Low water pressure can lead to a combi boiler ceasing to function properly. Check the pressure gauge; it should typically read between 1 to 1.5 bar. If the gauge shows a reading below 1 bar, that's an indication that water pressure is too low. To remedy this, one might need to repressurise the boiler's system according to the manufacturer's instructions.

Examining the Diverter Valve

The diverter valve, which directs water to either the heating system or the hot taps, can malfunction. Lukewarm water or no water at all from hot taps might signify a faulty valve. This requires the heating to be switched on for several minutes to test if the problem persists — a clear path should yield hot water subsequently. If not, the diverter valve may need repair or replacement.

Checking for Airlocks

Airlocks in the pipes can prevent water from flowing correctly. It is characterised by no water or just a trickle coming out of the hot water tap, whilst cold taps function normally. To resolve airlocks, it is often effective to attach a hosepipe to the problematic tap and another tap, ideally the cold water tap, to allow the water pressure to force the air out of the pipes.

Identifying Leaks and Blockages

Lastly, inspect for leaks or blockages within the system. Clogged pipes can obstruct the flow of water, as can leaks which reduce water pressure. It's vital to examine all visible pipework for signs of freezing or damage and check that the filters, such as the faucet aerator, are clear and free from debris. Blockages may require professional clearing, while leaks necessitate immediate repair to prevent further damage.

Troubleshooting Step by Step

When a combi boiler fails to deliver hot water, a systematic approach to troubleshooting can quickly pinpoint and resolve common issues, ranging from power supply problems to pressure discrepancies.

Resetting the Boiler

Should a power cut interrupt the energy supply, restoring power and resetting the boiler may resolve the issue. Locate the reset button typically found on the boiler's control panel, and press it as advised in the boiler's manual. Wait for the boiler to initiate the startup sequence, observing for any displayed error codes that could provide further insight.

Repressurising Your System

If the pressure gauge of the boiler indicates low pressure, repressurising your system might be necessary. The pressure should generally sit between 1 and 1.5 bar when the system is 'cold'. To adjust the pressure, locate the filling loop below the boiler, turn it to allow water into the system, and closely monitor the pressure gauge. Once the desired pressure is reached, firmly close the loop to prevent leaks.

Handling Error Codes

Modern boilers are equipped with diagnostic systems; thus, an error code on the display panel can reveal specific malfunctions. Refer to the boiler's handbook to interpret the error code which may point to issues with the boiler's timer, sensors, or internal components. If the boiler's error codes suggest serious problems or persist post resetting, it's prudent to contact a certified technician.

Dealing with Water Supply Issues

It is vital to confirm that the gas supply and water supply to the boiler are uncompromised. Check other taps to verify if the water issue is isolated or affecting the whole property. For a gas heater, if the ignition process fails, attempt to reignite the pilot light by following the manufacturer's instructions. Remember, only attempt as safe for your competence level and never hesitate to seek professional help when in doubt.

When to call a Gas Engineer

When faced with no hot water from a combi boiler, it is essential to understand when the expertise of a Gas Safe registered engineer is necessary for both safety and technical reasons.

Recognising Complex Faults

A homeowner may be able to perform simple checks, such as verifying that the thermostat is set to the correct temperature or confirming that the pilot light is lit. However, if radiators are warm but the showers and taps remain cold, or if there are signs of a leak, it is crucial to contact a qualified engineer. Complex faults such as issues with the diverter valve, pressure problems, or internal component failures require professional assessment and should not be tackled as a DIY task.

Gas Safe Engineers and Their Roles

A Gas Safe registered engineer is one who is legally permitted to work on gas appliances. They have the necessary certifications to ensure safety and competence. When contacting a professional, ensure that they are listed on the Gas Safe Register. These engineers have the skills to diagnose and suggest solutions for faults that might not be evident to the untrained eye. Their role is critical, especially when dealing with potential gas leaks or carbon monoxide issues that could pose a serious threat to health if mishandled.

Estimating Repair Costs

Repair costs can vary significantly based on the nature of the fault. While a minor fix may only involve the replacement of a small part, more serious problems might require the boiler to be replaced. Be prepared for an engineer's visit to include an initial diagnosis fee. After assessing the combi boiler, the engineer will advise on the cost of parts and labour. It is sensible to obtain a few quotations to ensure the price is competitive, but never compromise safety for the sake of cost.

A Gas Safe engineer is trained to provide safe and effective repairs. One should not attempt to fix complex boiler problems without the appropriate qualifications, as this can lead to further damage or, more importantly, endanger lives.

Maintenance and Prevention

Ensuring a combi boiler's reliability involves preventative measures and routine maintenance. Addressing common problems such as limescale, sediment buildup, and wear and tear can help avoid situations where no water is dispensed from the hot tap.

Regular Boiler Servicing

Routine servicing of a combi boiler is essential for its efficient operation and long-term health. During a service, professionals typically:

  • Inspect for signs of wear and tear or rust within the system.

  • Clean components like the heat exchanger, which can be prone to sediment buildup.

  • Check and adjust the system pressure to counteract any issues resulting from frozen pipes or clogged pipes in the winter months.

Servicing should occur annually to prevent the majority of common issues.

Addressing Hard Water Problems

In areas with hard water, limescale can accumulate, affecting the water heater's performance. To mitigate this:

  • Install a water softener which reduces mineral content before it enters the system.

  • Use limescale inhibitors that can be introduced into the water, slowing down the buildup of sediment.

These steps help maintain the efficiency of the combi boiler and extend its functional lifespan.

Implementing Timely Replacements

Components such as the faucet aerator and the radiator may suffer from sediment and limescale over time, which diminish the combi boiler’s effectiveness. Homeowners should:

  • Regularly inspect the aerator, and if blocked, remove sediment by immersion in a descaling solution.

  • Replace worn or damaged parts promptly to prevent further issues from emerging, as part of a DIY repair if they are confident in doing so, or by seeking professional help.

Taking these steps ensures optimal water flow and temperature regulation from the combi boiler system.

Do I Need A New Boiler?

When a combi boiler fails to deliver hot water, it can prompt concerns about the need for a new boiler. Before rushing to replace the unit, it is essential to examine the life expectancy and performance of your current combi boiler, as well as the financial implications of an upgrade.

Assessing Boiler Age and Performance

The lifespan of a combi boiler typically ranges between 10 to 15 years. If your boiler approaches the end of this spectrum, performance issues, such as no hot water from taps, may suggest it's nearing the time for a replacement. However, factors such as regular maintenance and the quality of the unit can extend this timeframe. An older boiler may also require more frequent and costly repairs, along with being less fuel-efficient. Checking the condensate pipe is prudent, especially in freezing conditions, as blockages here can mimic more severe failures.

  • Life Expectancy: 10-15 years

  • Checks:

    • Maintenance Frequency

    • Repair History

    • Fuel Efficiency

    • Condensate Pipe Condition

How Much is a New Boiler?

Boilers can be a daunting purchase for many people as they’re an appliance with a lot of responsibility, providing heat for you and your family is something you want to get right. Boilers aren’t exactly a quickly disposable item either, potentially lasting you a decade.

Effectively, new boiler cost can be split into two segments: the first is the actual boiler itself (unit price), and the second is the cost of the boiler being installed (set up) in your property by an expert engineer. 

Here at iHeat, we remove all of this undue stress and make the decision making process of upgrading to a new central heating system, as easy as possible.

New boiler costs can vary depending on a number of factors including their brand, model, fuel, output, warranty, labour and boiler installation type. Typically a new boiler will cost between £1,845 and £3,500, below is a list of average boiler installations offered by iHeat (guide only).

Installation Type

Price (inc VAT)

Combi to combi swap


Get a quote

System to combi conversion


Get a quote

New boiler install


Get a quote

Back boiler to a combi


Get a quote

System to system


Get a quote

Frequently Asked Questions

Why is there no water coming out of my hot tap?

There are several reasons why hot taps can run dry. One possibility is a malfunctioning diverter valve, which can fail to direct hot water to the tap. Another is a closed or incorrectly positioned filling loop, which might shut off the boiler's water supply.

Why is there no water coming out of my hot water pipe?

No water from hot water pipes suggests a serious issue such as a major blockage or a shut-off cold water supply. Checking for frozen pipes, especially during cold weather, is a good starting point as ice can cause blockages that prevent water flow.

Why is my combi boiler not giving hot water?

A combi boiler not providing hot water could be down to a few reasons including a faulty thermostat, a frozen condensate pipe, or a blocked plate heat exchanger. Limescale build-up is a common culprit in areas with hard water, restricting water flow through the boiler.

Why is my hot water not working but my cold water is?

If only the hot water is affected, this is often a boiler-related issue. It could be due to boiler settings like incorrect thermostat temperatures or timers. It's essential to verify the boiler's correct operation first before exploring pipework problems.

How do you remove an airlock from a hot water pipe?

To clear an airlock from a hot water system, you can use a hose to connect the hot tap with water failings to a working cold tap. Turn on the cold water to allow pressure to force the air back from the hot water system, thus clearing the airlock.

Can you get an airlock in a combi boiler?

Yes, an airlock can occur in a combi boiler's system, disrupting the flow of hot water. Typically, this results from trapped air in the pipes or radiators which inhibit the normal circulation of water.

What are the symptoms of airlock in hot water system?

Signs of an airlock include taps suddenly ceasing to emit water, spitting or spluttering when turned on, or a noticeable difference in water flow rate. Radiators failing to heat up entirely or only warming partially are also indicative of airlocked systems.

Stephen Day profile photo
Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.