Having no hot water can be frustrating and inconvenient, disrupting daily routines. Whether it’s for showers, washing dishes or laundry, a cold water supply is a hassle no one wants. This guide will help you identify common issues and provide practical fixes. Plus, you’ll know when it’s time to call a professional heating engineer to ensure your system is back in working order quickly and safely.

Top 5 common causes and how to fix them

1. Thermostat Issues

Cause:
The thermostat plays a crucial role in regulating the temperature of your water heater. If it’s faulty, incorrectly set or has stopped functioning altogether, your water may not heat up as expected – or at all. This is one of the most common causes of losing hot water in your home.

Fix:

Step 1: Check the temperature setting

  • Locate the thermostat on your water heater. You can normally find this near the control panel or temperature adjustment dial.
  • Ensure it’s set to a safe and effective temperature, typically 60°C. A setting too low might lead to lukewarm water, while a higher setting can be unsafe. The Health & Safety Executive (HSE) UK advises that this must be set to 60 and not below to prevent legionella

Step 2: Reset the thermostat

  • Follow the manufacturer’s instructions to reset the thermostat. Often, this involves turning off the power to the water heater, adjusting the thermostat and restoring power to allow it to recalibrate.

Step 3: Replace the thermostat if necessary

  • If resetting doesn’t resolve the issue, the thermostat may need replacing. Consult your water heater’s manual for guidance or call a professional heating engineer to ensure the replacement is done safely and correctly.

2. Pilot Light Problems (Gas Water Heaters)

Cause:
In gas water heaters, the pilot light is essential for igniting the gas burner, which heats the water. If the pilot light goes out, the burner cannot function, leaving you with no hot water. This is a common issue in older gas water heaters.

Fix:

Step 1: Check if the pilot light is out

  • Open the access panel on your water heater and look for a small flame. If you don’t see one, the pilot light has likely gone out.

Step 2: Relight the pilot light

  • Turn off the gas supply to the heater and wait a few minutes to allow residual gas to disperse.
  • Locate the pilot button and press it while using a long lighter to ignite the pilot. 
  • Continue holding the button for 30-60 seconds to ensure the flame stays lit.

Step 3: If the pilot light won’t stay lit, call a heating professional 

  • If the flame keeps going out, the thermocouple or gas valve might be faulty and needs replacing. 

3. Electrical Faults (Electric Water Heaters)

Cause:
Electric water heaters rely on electrical components such as circuit breakers and heating elements to function. A tripped breaker, a blown fuse or a damaged heating element can interrupt the heating process, leaving you without hot water.

Fix:

Step 1. Check the circuit breaker

  • Inspect your home’s electrical panel for a tripped breaker. If one has flipped, reset it by switching it off and then back on.

Step 2: Inspect the heating element

  • Turn off the power to the water heater and remove the access panel.
  • Look for visible signs of damage to the heating element, such as burns or corrosion.

Step 3: Replace the heating element if needed

  • If the element is faulty, it will need replacing. Consult your heater’s manual for compatible parts and hire a professional to safely replace it.

4. Sediment Build-Up in the Tank

Cause:
Over time, minerals and debris from hard water settle at the bottom of your water heater’s tank. This sediment build-up reduces heating efficiency, causes unusual noises and can eventually block the heating element, leading to little or no hot water.

Fix:

Step 1: Turn off the water heater

  • Turn off the power supply for electric heaters or the gas valve for gas heaters. Allow the water to cool before proceeding.
  • Drain the tank by connecting a garden hose to the drain valve at the base of the tank.
  • Open the valve and drain the water into a safe location.

Step 2: Flush out the sediment

  • Once the tank is empty, open the cold water supply to flush out the remaining sediment. Continue until the water runs clear.

Step 3: Refill and restart the heater

  • Close the drain valve, disconnect the hose and refill the tank. Turn the power or gas supply back on to resume normal operation. It’s worth noting that regular flushing (once or twice a year) can prevent future build-up.

5. Leaks in the System

Cause:
Leaks in your water heater or the connected plumbing can reduce water pressure and disrupt heating. Common causes include loose fittings, corroded pipes or damage to the tank itself. Significant leaks can also waste water and increase your utility bills.

Fix:

Step 1: Locate the leak

  • Inspect the tank, valves and pipes for visible signs of dripping or pooling water. Pay attention to areas around fittings and connections.

Step 2: Tighten loose connections

  • Use a spanner to gently tighten any loose fittings or connections. Avoid over-tightening, which could cause further damage.

Step 3: Apply temporary fixes for small leaks

  • For minor pipe leaks, use plumber’s tape or epoxy putty as a temporary seal until a professional can address the issue.

Step 4: Replace faulty components, and seek professional help if required

  • If a pressure relief valve or a pipe is the source of the leak, consider replacing the damaged part. If the leak is coming from the tank itself, it may indicate internal corrosion or damage that requires professional repair or replacement.

Prevention tips to keep the hot water flowing

Preventing hot water issues is easier and cheaper than fixing problems once they arise. Here are some simple ways to maintain your system’s efficiency:

Routine maintenance: Regularly flush your water heater to remove sediment build-up. Inspect connections, valves and pipes for any signs of wear or leaks. Test your thermostat to ensure it’s maintaining the correct temperature.

Water softener: If you live in an area with ‘hard water’ (i.e. water that contains high levels of minerals, mainly calcium and magnesium), consider installing a water softener. Hard water minerals can accumulate in your tank, leading to sediment build-up, reduced efficiency and a shorter lifespan for your system.

Professional check-ups: Schedule an annual servicing with a qualified heating engineer. A professional inspection can catch issues early, clean components and ensure all parts are functioning optimally, helping extend the life of your water heater and keeping your hot water supply reliable.

When it’s time to call the experts

Sometimes, despite your best efforts, your water heater issues may persist. Ongoing problems after troubleshooting, such as no hot water or recurring leaks, often indicate underlying issues that require professional expertise.

Signs of major problems:
Internal damage, such as corrosion or cracks in the tank, can lead to inefficiency or total system failure. If you notice rust-colored water, strange noises coming from the heater, or frequent pilot light issues, these are signs of significant wear or damage.

Safety concerns:
Gas or electrical water heaters pose potential safety risks. Gas leaks, faulty pilot lights or electrical faults could cause fires or other hazards. If you suspect such issues, it’s crucial to prioritise safety and avoid attempting repairs yourself. Professionals have the tools and knowledge to diagnose and resolve complex problems, ensuring your system operates safely and efficiently.

 

Got questions for the experts?

See our FAQs for Plumbers and Heating Engineers here

 

Quick troubleshooting and preventive maintenance

By understanding common causes – like thermostat problems, sediment build-up or leaks – you can often restore your system with simple fixes. However, some problems, such as internal damage or safety hazards in gas or electrical systems, require the expertise of a professional heating engineer. Regular maintenance, preventive measures and professional check-ups will help keep your water heater running efficiently, ensuring a consistent hot water supply and avoiding costly, long-term repairs.

FAQs

Why do I have no hot water?

You may have no hot water due to issues like a faulty thermostat, sediment build-up, pilot light problems or electrical faults. It could also result from leaks or damaged components in your system. Regular maintenance and troubleshooting can often pinpoint and resolve these problems.

Why is my boiler giving me hot water but no heating?

If your boiler provides hot water but no heating, it may be due to issues like a faulty radiator valve, a malfunctioning pump or air in the system. Low water pressure, thermostat problems or a broken diverter valve (i.e. the valve that directs water flow between heating and hot water functions), can also prevent central heating from working properly.

Why is there no water coming out of the hot water side?

No water from the hot side could result from a blocked pipe, a malfunctioning mixer valve or a faulty water heater. Sediment build-up, broken connections or issues with the water supply system can also prevent hot water flow throughout your household plumbing.

Why do I have water pressure but no hot water?

If you have water pressure but no hot water, it may be due to a malfunctioning heating element, a faulty thermostat or sediment build-up in the tank. Issues with the diverter valve or internal component failures in your water heater can also result in hot water not being delivered.

 

Paine Manwaring is an established, professional and highly experienced supplier of plumbing, heating and electrical services to domestic and commercial customers throughout Sussex, Surrey and Hampshire.

For more information about the heating, plumbing and electrical services which we provide for both homes and businesses get in touch with a member of our expert and friendly team today on 01903 237522 or enquiries@painemanwaring.co.uk (Worthing) or 01243 784711 or info@painemanwaring.co.uk (Chichester).