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No hot water? What to Check?

Apps Plumbing

22 feb 2021

What is a boiler service?

Finding out you have no hot water from the taps or shower is inconvenient. There are several possible causes for it. Some you can fix yourself, while others need an expert.

What to do if you have no hot water

Don’t panic! Whilst it can be frustrating, there may be a simple fix. Take a look through the checklist below to diagnose the problem before calling a Home Expert. There could be a quick and simple fix to get hot water running from your shower and taps again.

Check the boiler is working

The first thing to check when you have no hot water from your shower or taps is whether your boiler appears to be working or not. Here are two simple things to look at before considering more in-depth problems.

If you need more help, check out our guide on how to diagnose common boiler problems.

Check the display panel

The display panel of your boiler should be lit up with no error codes if working correctly. If the lights on the panel are off, your boiler could be switched off or have no power. If this is the case, jump to the water, gas and electricity supply section for further checks on your power supply.

If your boiler is on, has the display panel changed colour or does it show an error code? If it does, check your boiler’s instruction manual to find out what it means.

A reset will fix some faults. There may be a button on your boiler for this. If not, switch it off, wait a few minutes, then switch it on again.

Some error codes will show a more significant problem that requires a Gas Safe engineer. Your boiler manual should tell you if this is the case.

Is the pilot light on?

There’s a little window on the front of your boiler through which you can see the pilot light. It should be lit and burning bright blue.

If it’s orange or yellow, there could be carbon monoxide present, which is extremely dangerous. If this is the case, turn the boiler off and call a Gas Safe engineer immediately.

If it’s not lit, refer to your boiler’s instruction manual to relight it. If it doesn’t relight, there could be a problem with your gas supply. If it ignites, but keeps going out again, call a Gas Safe engineer.

Check the water, gas and electricity supply

If the checks above highlighted there’s no power or gas to your boiler, there could be a problem with your supply. It’s also worth exploring your water supply to resolve any water flow problems that could be causing the issue.

Water supply

Without removing the boiler cover, check if you can hear water flowing through the pump. Also, check there’s water coming out of the hot taps. If you have a conventional system, check the header tank that stores the water in your loft. If it’s low or empty, there could be a problem with the float valve.

If the header tank is full and water flows from the taps but doesn’t flow through the pump in your boiler, call a Gas Safe engineer.

Gas or oil supply

If the pilot light on your boiler is out and won’t relight, check your gas supply. If you’ve got other gas appliances, the easiest way to check your supply is to see if they’re working. If you don’t have other gas appliances, look at your gas meter to see if it’s on. If there’s no gas, contact your gas supplier.

If you use oil, check there’s enough in the tank by reading the gauge and get it refilled if necessary.

Electricity supply

If the boiler’s display panel is off or the pressure gauge is at zero, there may be no power to it.

  • Check the power to the boiler hasn’t been switched off.

  • Check if you have electricity to your lights and sockets. There may be a power cut.

  • Check your fuse box. Something could have tripped a switch to turn your electricity off.

  • If your home has power, check the fuse for your boiler and replace it if it’s blown. If it blows again, it indicates a problem with your boiler which requires a Gas Safe engineer.

Check the boiler settings

If there’s no hot water from the boiler, despite it being on and appearing to work, there are a few other easy fixes to try.

Is the boiler set correctly?

The settings on boilers can vary. Older models may only have a thermostat, while more modern boilers will have more options. If some of these controls aren’t on the boiler, they will be on your programmer instead.

Run through the list below to check everything is set up correctly for hot water:

  • Check the boiler or programmer is set to the ‘on’ position for hot water.

  • Check the thermostat is turned up high enough to produce hot water.

  • Check the boiler or programmer is set to ‘heating and water’ rather than ‘heating only’.

  • Try resetting your boiler. Press the reset button if there is one, or turn it off, wait a few minutes, then switch it on again.

Is the timer working?

Power cuts, failed batteries and the clocks changing can put your timer out of sync.

Check the time on the display and adjust it if it’s incorrect. The user manual will tell you how if you’re not sure.

Also, check when the hot water is set to go on and off. Ensure it’s on for long enough to heat the water adequately and supply enough for your needs. If there’s no hot water in the shower, you may have used it all before the boiler’s set to come on again.

Check the diverter valve

A diverter valve is found inside combi boilers. It opens and closes to provide hot water in both the radiators and the taps.

The valve should prioritise hot water over the heating. So, when you turn on a hot tap, it switches the flow from the radiators to the tap until you turn the tap off.

If you have heating but no hot water, the diverter valve could be faulty or stuck in the heating position. Or, if the central heating isn’t working but the hot water is, it could be stuck in the hot water position. Checking, repairing or replacing a diverter valve is a job that must only be carried out by a Gas Safe engineer.

Check the boiler pressure

If you notice the water from your hot taps is running at a lower flow rate than usual, you may have low water pressure.

Look at the water pressure gauge on the front of your boiler. It should show a reading of between one and two bars. Anything below one bar is low, while 2.75 bars and above is high.

If your pressure is too low, you can usually repressurise your boiler yourself.

Water leaks can also cause drops in water pressure. So, if your pressure is still low after re-pressurising, jump to the next section for advice on leaks.

Check for leaks

Water leaks can cause the pressure to drop, which in turn stops your hot water working. Some leaks can be so small that the pressure drop is very gradual.

To detect a water leak in your home check for damp patches in the following places:

  • Around radiators

  • Around pipes

  • Around your boiler

  • On ceilings

  • Flaking paint or swollen woodwork.

Don’t look for leaks inside the boiler unit itself. Just look around the outside without taking the cover off. If you need more help check how to diagnose a leaking boiler and call a Gas Safe engineer if you diagnose a leak.

Top tip: Make sure you don’t mistake condensation for a leak.

Check for frozen pipes

If your hot water is not working when temperatures have been very low, you could have a frozen pipe. Signs of frozen pipes are:

  • There’s no water from the hot taps or only a trickle

  • You can visibly see a pipe is frozen over

  • You notice odd smells coming from taps or drains

The most likely places where pipes can freeze are:

  • Anywhere that pipes haven’t been sufficiently insulated

  • At the point where pipes enter your home

  • Pipes inside cupboards where warm air can’t reach them

  • Your boiler’s condensate pipe. This carries condensation from the boiler to the drain outside

  • Try thawing out frozen pipes by pouring hot (but not boiling) water over them or use a hot water bottle.

Check the radiators

If your boiler’s working but there’s no hot water, check your heating. Are the radiators cold when the heating’s on, or are there cold spots?

If there are, there could be a build-up of matter inside the radiators, restricting water flow. A heating engineer can fix this issue by conducting a system Powerflush.

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