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Not hot water from your boiler? Common reasons why (with fixes)

No hot water from you boiler? What next, no butter on your toast? The world isn’t fair. Plus, sometimes you won’t get hot water from your boiler. Even if you have heating.

The point at which people no longer have access to hot water is the point at which they’re most likely to ironically boast about their mindfulness on Facebook, wear Crocs or start a ‘fresh Instagram’ account.

Avoid this.

No hot water from a combi boiler: Top reasons why (with costs to fix)

#1 - Pilot light not lit (no flame = no hot water)

No Hot Water - Pilot Light

Boilers burn gas (or oil) – and to do so require a pilot light.

Pilot lights are tiny Olympic flames which carry the whole weight of a family’s comfort and well-being.

In some ungodly circumstances, this flame could go out or more commonly, just fail to catch. This will lead to total failure, meaning you'll get no hot water from your boiler.

In older boilers, you might actually be able to see the pilot light through the framework of your boiler, but in more modern boilers, you’ll be alerted of its failings through an error code on a depressing black & white monitor.

Through referencing your boilers manual, attempt to relight the pilot light.

If that doesn’t work – you will require a heating engineer to tend to your broken boiler – hopefully, you won't need a new one (if you do, learn more about the best combi boilers).

Luckily, in most cases, this'll be a DIY fix, and a quick (free) way to get your boiler's hot water back.

Cost to fix (and get your hot water back):
DIY: £0.00
Engineer: £75-£160

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#2 - Frozen pipes

No Hot Water - Frozen Pipes

Barring a global nuclear disaster, this will only apply to winter conditions.

A condensate pipe leads from our boiler to an outside wall (or sometimes an internal drain) and allows for the expulsion of condensation water.

Due to the slow drip of water and the predictable nature of physics, this will occasionally freeze over. Upon detecting this, your boiler will shut down for safety reasons, giving you no hot water (or heating) at all.

Fortunately, this is easily fixed at home by slowly melting the frozen area by wrapping the pipe in cloth or pouring some warm water over the condensate. You’ll need to reboot your boiler after addressing this.

Once done, your boiler should have it's hot water back.

Cost to fix (and get your hot water back):
DIY: £0.00
Engineer: £50-£150

#3 - Diverter valve

No Hot Water - Diverter Valve

Inside every boiler lies a diverter valve.

It's a miniature traffic director dictating the flow of water like an outcasted member of the X-Men.

A failure of this device, potentially caused by natural system corrosion or metallic built up over time might only allow for hot water to be delivered to your radiators and starve the hot water supply – hence, no hot water from your boiler.

Outside of a potential error code alter, it isn’t something you’ll be able to diagnose at home and a heating engineer is most definitely required.

Best case scenario here is a diverter valve replacement that might set you back around £200 with labour costs but take into account the age and condition of your boiler before throwing repair money at it.

If your boiler is broken beyond repair, we fit new Viessmann boilers with 10-years parts and labour warranties from £1,695 (all over the UK).

Cost to fix (and get your hot water back):
DIY: Impossible
Engineer: £180-£250

#4 - Pressure issues: Over or under pressurisation

No Hot Water - Boiler Pressure

With the likely culprit being the aforementioned leakage, under or over pressurisation could result in no hot water from your combi boiler.

If your boiler is low on pressure, it can usually be solved simply through a DIY top up. 

An over pressurised boiler can also be combatted at home through some simple radiator bleeding but if that wasn’t to solve the issue, it’s a broken boiler part requiring a heating engineer or a new boiler that’s the source of your lack of hot water.

Cost to fix (and get your hot water back):
DIY: £0.00
Engineer: £50-300

No hot water from a regular/system boiler: Top reasons why (with costs to fix)

Receiving heating but no hot water from your boiler is more likely with a conventional or system boiler that has a hot water cylinder.

#1 - Thermostat/timer fault

No Hot Water - Timer Fault

If you’re savvy with your tech or keep a watchful eye on your energy usage, you’ll likely be using your boilers timer to control when it’s in operation. A thermostat issue would only cause an issue with heating, rather than hot water.

But if your thermostat is also acting as a timer, a fault with it might cause your boiler to shut off entirely, also starving you of hot water and plunging you back into an age so dark you feel blindfolded.

Cost to fix (and get your hot water back):
DIY: £0.00

#2 - Boiler or pipe leak

No Hot Water - Boiler Leak

A leaking boiler or pipe will most likely lead to a pressure drop, which you can read about in almost perverted detail in this boiler pressure article.

This leak will result in an inadequate water pressure level affecting the delivery of hot water to your taps.

General losses of boiler pressure can be resolved by topping up your pressure manually but if this is caused by a leak, then this will need to be addressed by a professional.

Cost to fix (and get your hot water back):
DIY: £0.00
Engineer: £100-300

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#3 - Energy source failure – gas or electric 

No Hot Water - Energy

A lack of either electricity or gas to the boiler is the most obvious and common reason for a lack of hot water and will result in you being officially declared a silly sausage for Googling why your boiler is not working.

We won’t go into comprehensive detail about how to check if you have a gas or electric supply but start by checking other nearby appliances aren’t affected, be it lights or a gas cooker. Oh – and not forgetting to check if your boiler is switched on to start with.

Cost to fix (and get your hot water back):
DIY: £0.00 (unless you've failed to pay your energy bills)
Engineer: £50-300

#4 - Inadequate water cylinder size

No Hot Water - Cylinder Size

If you’re not getting hot water from your regular/system boiler then it might be that the cylinder isn’t adequate for your hot water requirements.

Cylinder sizes range greatly with smaller ones being suitable only for houses occupied by up to two Hobbits with a much smaller hot water demand.

If you’re fond of particularly lengthy showers as you wash away the sins of your poor boiler buying decision or you’re a family of standard sized humans then your hot water will run out in no time at all.

The only cure for this is; less hot water or more tank.

Cost to fix (and get your hot water back):
DIY: Impossible
Engineer: £500-700 (+ fitting)

Getting no hot water from your boiler? Here's a skim-readers conclusion

Having no hot water from your boiler comes with a diverse range of suspect reasons, that could cost anywhere between nothing and a small fortune depending on which company you approach to resolve the issue.

The most important things to remember when you've got no hot water

#1 - If you’re not getting hot water from your boiler – explore every possible free/DIY fix (mentioned above). After exhausting these, educate yourself on the most likely reasons why your boiler's not working before consulting professional help so you’re aware what you should be being charged – not what a spanner wielding joker fancies charging you for Friday afternoon.

#2 - If your boiler requires a costly repair, consider the age of your boiler and the likelihood of the boiler having further issues in the near future.

If your boiler is 10 or more years old and has problems associated with age/corrosion, or regularly leaks – seriously consider a new boiler. Can’t afford that? Check out boilers on pay monthly plans, with no deposit or 0% options. 

For a massive article on prices, check out our new boiler costs article.

'Big' boiler brands can stop giving hot water too

On the off chance your boilers manual isn’t your fave book -  here are some common error codes for common boilers.


No hot water from Worcester boiler

No Hot Water From Worcester Bosch Boiler

Error Code No Hot Water Reason
A1 Water leak in pump
EA No flame (pilot light)
FD 231 Mains power fault
F0 238 Valve error
356 Low voltage
EA 229 Condensate pipe frozen
356 Low mains voltage

Applicable Worcester Bosch boiler models:
Worcester Bosch CDi Classic, Worcester Bosch CDi Compact, Worcester Bosch Greenstar i, Worcester Bosch Greenstar Ri.


No hot water from Vaillant boiler

No Hot Water From Vaillant Boiler

Error Code No Hot Water Reason
F.24 Pipe blockage
F.29 Pilot light failure
F.61 Valve failure
F.21 Pilot light not lighting

Applicable to Vaillant models:
Vaillant EcoTec Pro, Vaillant EcoTec Plus, Vaillant EcoPure, Vaillant TurboMax.


No hot water from BAXI boiler

No Hot Water From BAXI Boiler

Error Code No Hot Water Reason
H.01 Connection failure to gas
H.03 Pilot light failure
E.01 Frequent pilot light fault
F0 238 Valve error
356 Low voltage
EA 229 Condensate pipe frozen
356 Low mains voltage


No hot water from Ideal boiler

No Hot Water From Ideal Boiler

Error Code No Hot Water Reason
F1 Water leak in boiler/system

Ideal boilers tell you literally everything else on screen.

If you read the entirety of this article, you’re now endowed with an online PHD, majoring in the theoretical theory of ‘no hot water from boiler’.

It’s approximately as useful as British Gas customer service advisor but does afford you the freedom to confidently wear a tweed jacket with leather elbow patches.

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Heatable is registered in England and Wales No. 08804726 (VAT No. GB205805920 ). Trading address is 1 Station Road, Great Sankey, Warrington, Cheshire, WA5 1RH. Heatable acts as a credit broker (not as a lender) and offers credit products through a panel of lenders. Heatable is authorised and regulated by the Financial Conduct Authority (reference no. 805259).

[1] Price based on a like for like combi swap in a 2 bed, 1 bathroom terraced home with a standard flue

[*] Installation dates are subject to installer availability

[¹] only available on combi boiler installations