Boiler Not Working? (10 causes and fixes) Re January 17, 2020

Boiler Not Working? (10 causes and fixes)

engineer servicing a boiler

What are the solutions for common boiler problems? we discuss low pressure, no heat/hot water, boiler leaking, strange noises, etc.

WarmZilla exists to make buying a boiler easier and cheaper for you as a customer, we do want to sell you a new boiler but we also want to save you money. With that in mind, we decided to put together a list of the 10 most common boiler issues and ways of fixing them (where possible).

If the issue is too serious to fix then you’re in the right place to get yourself an online boiler quote in a couple of minutes. You can either take our 90-second survey which asks you about your current heating system and what you’re looking for, or your can use our Boiler Comparison tool, which allows you to compare your current boiler against other boiler models or brands, or even compare three new boiler models to see which one is the most suitable for your home.

Prevention is better than cure

We’d like to start off by saying that the best way of avoiding issues with your boiler is to ensure it’s well-maintained. Make sure you get your boiler serviced every year, this will keep your boiler ticking over and pick up minor issues before they become majorly expensive issues.

Don’t take the cover off your boiler

Unless you are a Gas Safe registered engineer, do not attempt to take the cover off your boiler, there are secrets behind the cover that no mortal should ever know – plus it’s the law. No matter how handy you may be, leave it to a trained professional. Some things just aren’t worth taking chances with and your boiler is one of them.

1. Boiler losing pressure

A boiler losing pressure is usually a sign that there is a leak somewhere in your system. Check underneath your boiler for any drips, if you find any, then it could be that a seal has gone inside the boiler. 

If there are no leaks around the boiler, take a look at the radiators in your home, specifically the pipes leading into the radiator and the radiator valves that control the temperature. Take a dry cloth or toilet paper and rub it on the joins to see if there is any excess water.

If the water is coming out of the join to a radiator valve then you may be able to fix the problem yourself with relative ease. If the radiator thermostat (temperature control) is leaking then you may need to drain down the system and replace the faulty thermostat.

Another common cause of a boiler losing pressure occurs after the radiators have been bled. When you bleed your radiators, air is released from the system, this lowers the pressure within your boiler. To fix this you will need to repressurise your boiler by following the steps below.

If your boiler still won’t repressurise, then you either have a leak or your pressure relief valve needs attention. Don’t keep trying to repressurise the system if it isn’t working, call out a Gas Safe engineer to take a look.

How to fix: 

  • Boiler leak: If your boiler is leaking, then you will need to call a Gas Safe engineer as it could be a seal needs replacing. 
  • Radiator leak: If you locate a leak around your radiators then you may be able to fix it yourself by tightening the gland nut. If it still leaks, loosen the gland nut and wind some PTFE tape around the spindle and then tighten it back up.
  • Thermostat leak: If the radiator thermostat is leaking then you, or a Gas Safe engineer, will need to drain down your system so that the faulty valve can be replaced.
  • Repressurise boiler: Each boiler is different and we recommend checking your boilers manual or with your boiler manufacturer if you don’t have the manual. But generally, you can follow the steps below:
    • Switch off your boiler and let it cool completely
    • Find the filling loop (flexible silver cable) and make sure both ends are tight or you may have an internal filling key but it’s the same principle.
    • Open bath valves or turn your internal filling key to allow cold water into the system, this will repressurise the system.
    • When the gauge reaches 1.5 bar close both valves.
    • Remove the filling loop if it isn’t a permanent attachment.
    • Turn the boiler back on.
    • Check-in a few days to see if it has lost pressure again.

2. No heating or hot water

This is quite a broad fault and could be related to a few different issues – faulty thermostat, valve failure, pressure loss, tripped fuse, no credit on a pre-paid meter or a broken pump.

How to fix:

  • Low pressure: If the pressure is low then refer to the steps above for repressurising your boiler. 
  • Faulty thermostat: Smart thermostats can lose connection to the boiler as they are dependent on an internet connection. On standard thermostats, make sure the timer is set at the right time and that it’s set to on.
  • Tripped fuse: Check to see if any of the fuses have tripped over, if they have flip them back. If they trip again you will need to get a professional to take a look and diagnose the issue.
  • No credit: This one is pretty simple, if you have no credit on a pre-paid meter then you will need to add some.
  • Broken pump: If you have a problem with your pump then it’s not something you can fix yourself, you will need to find a Gas Safe engineer from the Gas Safe Register.

If the problem isn’t connected to the issues above then it’s more than likely a faulty part within the boiler so you will need to call out an engineer.

3. Boiler leaking

A boiler can leak for a wide variety of reasons but whatever the reason may be, we recommend you call an engineer immediately and get them to take a look. As a further precaution you may wish to turn off your water supply and heating.

Continuing to use a leaking boiler, or worse, ignoring the issue will only lead to further damage to your boiler and possibly to your home if the leak worsens.

Causes of a leaking boiler can include any of the following issues –

  • Pressure: If your boiler’s pressure is too high it may cause a leak to vent some of the excess pressure.
  • Pump seals: Your boiler houses a water pump that pumps water around your system, sometimes the seals can wear over time and water can escape.
  • Temperature Control Valve (TCV): Defective TCV’s can mean the water temperature isn’t regulated and the temperature can cause a leak if it gets too high.
  • Loose joints: Whilst good on a human, loose joints on a boiler are bad news. Over time joints can loosen due to repeated heating and cooling expanding and contracting the pipe joints. They may need tightening or resoldering if this is the issue.
  • Corroded pipes: If your pipes have started to corrode then the system will need to be checked and all signs of corroded pipes replaced.
  • Ageing boiler: After a certain amount of wear-and-tear a boiler can start leaking because it needs to be replaced. If your boiler is over 10-years old and leaking, you may be better off thinking about replacing it rather than repairing it.

How to fix: Do not attempt to fix this issue yourself, you will need to call in the cavalry on this one.


4. Banging, gurgling or whistling noises

If your boiler is making any of these noises, don’t try and communicate with it yourself, get a Gas Safe engineer who has been trained in the ancient art of boiler whispering to diagnose the issue.

It could be that some air has got into your system, the water pressure is too low, your pump is on the way out or your boiler is ‘kettling’. Kettling isn’t a process of retraining your boiler is undergoing because it fancies a career change, kettling is caused by a build-up of limescale or sludge in your boiler’s heat exchangers. This is a result of the limescale within the cold water which enters the primary central heating system or secondary heat exchanger.

This build-up restricts the flow of water in the heat exchanger, overheating the water, causing a noise like that of a boiling kettle to occur. If you would like to learn more about what a heat exchanger is and how they work, we have a separate blog that covers this. 

Are there ways of avoiding excess build-up and sludge? The answer is yes. Before you go ahead and pay the expenses of your local Gas Safe Engineer, it may be worth looking into water softeners. 

A water softener is designed to remove minerals that create water hardness, which is one of the most common water quality problems a homeowner encounters. A water softener is a filtration system that removes the calcium and magnesium ions that can be found in hard waters that enter your home. As the hard water is passed through good-grade resin beads within the filter, sodium ions are released into the water, making it soft.

How do you know if you need a water softener? Well, if you’re living with decreased pressure from scale-ridden pipes, dry hair, stiff laundry, and endless appliance repair bills, you need a water softener. Hard water will not go away on its own and the costs incurred by hard water will only continue to escalate. If scale continues to accumulate in your pipes, your flow rate will continue to restrict and you risk losing water pressure throughout the house. 

If you require a new boiler and you have a water softener, it is imperative that you either consult the manufacturer to see if the boiler once installed will be covered under the guarantee, or search for the new boiler installation and servicing instructions to see if the particular boiler of your choice can be installed with one. Not all manufacturers allow water softeners with their boilers.  

How to fix: Do not attempt to fix this issue yourself, you will need to call a Gas Safe engineer to perform a power flush or chemical flush on your heating system. 

If you’re planning on moving home, it’s worth testing your boiler before you move, and replacing it if it’s making any strange noises, other top tips on home improvements here – ‘Improving Before Moving: A Room by Room Guide‘.

5. Pilot light going out

If your pilot light is repeatedly going out then it could be to do with a draft, the pilot light needing a clean, an issue with the gas supply or you have a broken thermocouple.

Before trying to reignite the pilot light, ensure there are no issues with your gas supply. Check that your home appliances are receiving gas and work as normal. Make sure that when you try and relight the pilot light you follow the manufacturer’s instructions.

If you’re still having issues relighting your pilot light then call a Gas Safe engineer.

How to fix: Check the gas supply is working in your property by checking other gas appliances to ensure they have a gas supply. If you have gas but you can’t light the pilot light try cleaning the area of the pilot light, it could be some dust or debris has gotten into the area and is stopping the flame from igniting. If you have a broken thermocouple then you will need a Gas Safe engineer to help you.

6. Frozen condensate pipe

We’ve already covered how to fix a frozen condensate pipe in another article, and we recommend reading that if your condensate is frozen.

A condensate pipe is a waste pipe that carries acidic water safely away from your boiler into a drain. It will be either 21.5mm white, plastic pipe or 32mm white, plastic pipe.

Water in the condensate pipe can freeze when exposed to very cold temperatures. When this occurs, the boiler will continue to dispose of this waste water, but as it now has nowhere to go due to the water freezing and essentially blocking the route to the drain, it backs up into the boiler.

Your boiler will then lock itself out to prevent any damage and will let you know via a fault code or a sequence of fault lights, depending on what boiler you have. Another giveaway of a blocked condensate pipe is you might be able to hear a gurgling noise inside the boiler.

How to fix: Once you’ve located the frozen part of your condensate pipe then pour warm water over it until the blockage disperses in a civilised manner. Avoid pouring boiling water as this could damage the pipe. You can lag the pipe to prevent the issue from happening again in the future…

7. Radiators not fully heating up

This issue is usually down to sludge building up in your system and settling in your radiator. Sludge is formed from rust that has corroded from the metalwork inside your heating system. When WarmZilla install a new boiler, we always add inhibitor to your heating system, this coats the metal and helps to prevent corrosion.

Another cause for radiators not heating up can be down to air in your system, if there are air pockets in your radiator then the water won’t be able to heat up that part of the radiator.

How to fix:

  • Sludge build-up: You can try adding inhibitor to your system but if the sludge has already settled it’s unlikely to have any impact. You will need to get a powerflush, this is a machine that is connected to your system and targets that stubborn sludge build-up by attacking it with very high-pressure water flow together with a powerful system cleaning agent.
  • Air pockets: This is quite an easy fix, you just need to bleed your radiators. Take your radiator key (if you don’t have one you can pick them up in hardware stores) and insert it into the slot usually found on the top right of your radiator. Turn the key and you should hear a hissing noise as air escapes. Once all the air has escaped a trickle of water will come out so be sure to have a cloth ready. You may need to repressurise your boiler after bleeding the radiators. Follow the instructions in step one of this post to do just that.

8. Heating not coming on at the right time

This issue is often linked to a faulty thermostat. Just check that your thermostat is set to the right time and it’s switched on, sometimes when the clocks change the thermostat will get out of sync with your heating demands.

If you have a smart thermostat, it might have lost connection to the internet or just need the classic fix ‘turn it off and back on again’, this works for 95% of all electrical issues.

How to fix: If there is an issue with a standard thermostat then you will need to call a heating engineer to replace it. If you have an issue with a smart thermostat, check that it’s connected to the internet, if not try resetting your internet and turning the thermostat off and back on again.

9. Water is too hot

If the water in your central heating system is coming out of taps too hot then there are a few things it could be related to. Firstly, try turning the water temperature setting down on your boiler, there may not be a mechanical fault just a setting that’s too high.

Another issue could be that your thermostat within the boiler is faulty and can no longer regulate the water temperature.

How to fix: Turn the temperature dial down on your boiler, if that doesn’t work then it’s time to call in a heating engineer to fix that faulty thermostat. If your boiler is getting on in years you may want to get a quote on a new boiler rather than sinking money into a boiler that is likely to fail again.

10. Boiler turns itself off

This can be related to a lot of different issues. Most modern boilers will lock out if they encounter a fault that can be harmful to the boiler.

It could be due to a loss of pressure in the system, a problem with the thermostat, a closed valve, a pump issue, or any number of other, hard-to-diagnose issues. If you can’t diagnose the issue then we recommend calling out a local Gas Safe engineer to take a look at your system.

How to fix: Check your boiler to see if there is a fault code like ‘E74’ on the digital display, search on the boiler manufacturer’s website for what that error code refers to. Some issues you may be able to fix yourself but others you will need to call out a Gas Safe engineer.

WarmZilla have quite a few videos on our YouTube channel that diagnose fault codes and offer fixes.

We hope this guide has helped you diagnose and hopefully, fix your issue. If you need a gas safe engineer then please check the Gas Safe register for your local expert. If your boiler is reaching the end of its life then why not get a WarmZilla quote on a new boiler? We offer finance packages starting from as little as £10.68 per month. Remember to use our Boiler Comparison tool to help you find your perfect boiler. 

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