It can be frustrating to find yourself without hot water. If that's happened to you, but your central heating system seems to be working, don't worry.
Our troubleshooting guide outlines the most common causes of hot water failure, specific checks based on your boiler type, and when it's time to call in a Gas Safe engineer.
The 10 most common reasons for having no hot water in your home
When your central heating system is working, but you're not getting any hot water, it can be frustrating. Here are some of the most common causes and what you can do to troubleshoot the problem.
1. Gas, electric and water supply
First things first—check your gas, electric, and water supply. It's an obvious step, but sometimes, these essential utilities can be accidentally turned off or disrupted.
Make sure all switches are on, and your water supply is running. This simple check can save you from more complex troubleshooting.
2. Thermostat settings
Your thermostat controls the temperature of both your heating and hot water. If it's set too low, you might not get hot water at all.
Ensure the temperature is set high enough to trigger the hot water function. Adjusting the thermostat might be all it takes to solve your problem.
3. Boiler's clock and timer
Sometimes, the issue could be with your boiler's clock or timer. If these settings are incorrect, your hot water may not come on as scheduled.
Verify that the clock and timer are set correctly to ensure your boiler heats water at the right times.
4. Pilot light
The pilot light is crucial for gas boilers. If it's gone out, you won't have hot water. Follow your boiler's manual to relight the pilot.
If it keeps blowing out or if you suspect a gas leak, call a Gas Safe engineer immediately.
5. Water pressure issue
Low water pressure can prevent your boiler from heating water effectively. Check the pressure gauge on your boiler. It should ideally be between 1 and 1.5 bar.
If it's lower, you might need to re-pressurise the system using the filling loop, following your boiler's manual instructions.
6. Recent power cut
A recent power cut can sometimes reset your boiler to factory settings, affecting its performance. Check your boiler settings and make any necessary adjustments to restore normal operation.
7. Frozen pipes
In cold weather, pipes, particularly the condensate pipe, can freeze. This can block the flow of water and prevent your boiler from working properly.
Pour warm (not boiling) water over the frozen pipe to thaw it. If the problem persists, consult a heating and gas engineer.
8. Possible leaks
There are many reasons why your boiler might be leaking water, but whatever the reason, leaks can reduce your boiler's pressure and affect its ability to heat water. Check for any signs of leaks around your boiler, pipes, and radiators.
If you spot any, they should be fixed promptly to restore normal function. If you're not comfortable trying to patch the leak yourself, call in a Gas Safe registered engineer, and they'll be able to get it sorted in no time.
9. Water tank or cylinder issue
If you have a water tank or cylinder, issues here can also lead to no hot water.
Check the tank thermostat and ensure it's set correctly. Your boiler's manual should reference any error codes or unusual displays.
10. Boiler needs resetting
Sometimes, your boiler needs to be reset to start working correctly again. See our full guide on how to reset your boiler here.
If this doesn’t work, there may be a deeper issue at play.
Boiler specific checks
Different types of boilers come with their own set of potential issues that can lead to a lack of hot water. Knowing what to look for based on your boiler type can help you pinpoint the problem more accurately.
Whether you have a combi boiler, gas boiler, electric boiler, or open-vented system boiler, follow these targeted checks to troubleshoot and resolve common issues related to your hot water supply.
Combi boiler or sealed system boiler
Diverter valve
If your central heating is working but you’re not getting hot water, the diverter valve might be at fault. This valve directs hot water between your radiators and taps. When malfunctioning, it may fail to switch properly, resulting in no hot water.
If you suspect a faulty diverter valve, you’ll need a Gas Safe registered engineer to replace it, as it’s not a repair that can typically be handled without professional help.
Low water pressure
For both combi and sealed system boilers, low water pressure can lead to no hot water. Check the pressure gauge and use the filling loop to adjust if necessary.
If you’re not comfortable doing this yourself, or if the pressure drops frequently, consult a professional to investigate possible leaks or other underlying issues.
Gas boiler
Pilot light
One common cause of no hot water in a gas boiler is a faulty pilot light. The pilot light ignites the gas that heats the boiler's water.
To address this, follow the manufacturer’s instructions to relight the pilot. If the pilot light keeps going out, it could indicate a problem with the thermocouple, which is a safety device that ensures gas doesn’t leak when the pilot light is off. In such cases, it’s best to consult a Gas Safe engineer.
Faulty pressure relief valve
The pressure relief valve helps regulate the pressure in your boiler by releasing excess pressure to prevent damage. If this valve fails, it might cause fluctuations in water pressure or lead to leaks.
If you suspect a faulty pressure relief valve, replacing it is usually the solution. This task can be complex and may require professional assistance to ensure it’s done correctly.
Leaks
Leaks in a gas boiler can result in low pressure and inadequate hot water. Check around your boiler for signs of water leakage, such as wet patches or puddles. Common leak sources include the pressure relief valve and other connections.
If you identify a leak, it’s crucial to address it promptly. Small leaks can sometimes be fixed by tightening fittings, but significant leaks or those from the tank itself will require a professional’s help.
Gas supply
Ensure that your gas supply is functioning correctly. If other gas appliances in your home are also not working, the issue might be with the gas supply rather than the boiler.
Check for any interruptions in your gas service or contact your gas supplier to confirm that your supply is active. If you suspect a gas issue or smell gas, it’s essential to contact a Gas Safe engineer immediately for safety reasons.
Electric boiler
Circuit breaker
If your electric boiler isn’t working, check the fuse box to see if the circuit breaker has tripped. A tripped breaker can interrupt the power supply, preventing your boiler from heating water.
Reset the circuit breaker or replace any blown fuses. If the problem persists, you may be dealing with a more serious electrical fault, which will require an electrician’s expertise.
Heating elements
Electric boilers use heating elements to warm the water. If hot water is insufficient or not hot at all, one or both heating elements might be faulty.
You’ll need to test these elements with a voltage tester. If you’re not familiar with working with electrical components, it’s safest to contact a professional to check and replace faulty elements.
Thermostat
The thermostat in an electric boiler controls the water temperature. If it’s malfunctioning, you may experience inadequate hot water.
Since accessing and adjusting the internal thermostat can be complicated and potentially dangerous, it’s recommended to have a qualified engineer handle this.
Open-vented system boiler
Float ball valve
If you have an open-vented system boiler with a water tank, a stuck float ball valve could prevent proper water flow into the system.
Check the water tank in the loft to ensure that the float ball valve isn’t stuck. Gently move the valve to free it, but be careful not to force it. If you’re unsure or if the issue persists, consult a professional.
When is it time to call in a JustFix professional?
If you’ve gone through these checks and still have no hot water, it may be time to call a JustFix professional. Issues like a malfunctioning diverter valve, persistent leaks, or problems with the pilot light often require expert attention.
Our Gas Safe registered engineers can diagnose and repair your boiler issues quickly and effectively. We also offer an annual boiler service so you can prevent future issues and keep your boiler running smoothly for years to come. Find a local heating and gas engineer in minutes with JustFix.
