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Last updated: 18th April, 2024


No Hot Water From Boiler?

No Hot Water From Boiler?

Some of the most common reasons for not getting any hot water from your boiler.

There are many things that can go wrong with a boiler that can result in the unit no longer providing the property with hot water.

Let us take a look at some of the most common reasons you might be experiencing an issue with your boiler.

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Frozen Pipes

If you're not getting hot water from your boiler in winter, it may be because your pipes are clogged up with ice.

There's a section of piping that runs from the back of your boiler to an outside wall of your house, called the condensate pipe, which can sometimes freeze in cold conditions, which the UK is extremely familiar with!

When your condensate piping freezes, your boiler will automatically shut off for safety reasons, leaving you without heating or hot water until you defrost the frozen piping.

Slowly melt the ice on the pipe by either wrapping it in cloth or pouring warm water over it.

Once the ice has gone, simply reboot your boiler to restore your hot water supply.

The Pilot Light

All boilers burn fuel such as gas or oil, and this requires a working pilot light to do so.

Sometimes, your pilot light may go out, or might just fail to light when you get your heating system started up. This leads to a complete system failure, with no hot water from your boiler being provided at all.

If this happens, you can find help and a guide to relighting your pilot light in the back of the manual for your boiler.

In most cases, you'll be able to fix this fault yourself and won't need to call a registered engineer out at a cost to get things working again.

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Pressure Problems

Pressure problems can be a fiddly fault to deal with. In the best case scenario, your boiler might have too low water pressure to move hot water around your home efficiently.

All you need to do in this situation is a one time top up with more water.

Alternatively, if your boiler pressure is too high , this can be more of a serious issue.

You may be able to fix it with some radiator bleeding, but if that doesn't help you'll want to call in engineers to take a proper look around the tank and find out what new parts you need.

The Diverter Valve

An important component of combi boilers is the diverter valve.

This directs the flow of water between your central heating and hot water supply, and if it fails, then one of those systems is going to lose out.

The problem is that you can't do much about this problem on your own, so you're going to need to get a qualified, gas-safe engineer in to fix it as soon as possible.

You may require a new displacer valve, which isn't cheap, but it will still probably cost less than an entirely new boiler.

Thermostats and Timers

If you have got a relatively new boiler with a thermostat and a timer to control when you have hot water during the day, then a fault in this component could cause your boiler to shut down completely, depriving you of hot water and heating.

This sort of system boiler is easy to fix, and often develops problems in the event of a power cut.

Energy Source Problems

A very common explanation for a lack of water heating is a problem with either the power or gas supply to your boiler.

Check your fuse box to make sure it is not just a tripped fuse, and then check other nearby gas appliances and electrical appliances near your boiler tank.

It is also worth checking that your boiler is actually switched on, and that the timer and that your thermostat isn't set to the wrong settings!

If any of your other appliances seem to be lacking power, then the best thing to do is to call in a gas safe engineer to help you deal with things.

Leaks in your Water Supply

A leak in your boiler or pipe will lead to a pressure drop, your pressure gauge crashing down to a low number, and no hot water coming out of the hot tap, as discussed above.

In general, you can fix low pressure by topping up your boiler manually, but if it's caused by a leak, then you'll need to find a gas safe engineer to make sure everything is properly fixed up with no further leaks.

You can't easily fix a leaky pipe on your own, so check to make sure this is the problem and then hire a professional to help fix your heating.


Before you call an engineer, you should always make sure that they are registered in England and authorised and regulated by the financial conduct authority for your safety and security!

If you have a more modern boiler, it might display a specific error code for each different problem that may cause a lack of hot water in your home. It's worth having a check on that for an easier diagnosis!

iHeat New Boiler Costs

Boilers can be a daunting purchase for many people as they’re an appliance with a lot of responsibility, providing heat for you and your family is something you want to get right. Boilers aren’t exactly a quickly disposable item either, potentially lasting you a decade.

Effectively, new boiler cost can be split into two segments: the first is the actual boiler itself (unit price), and the second is the cost of the boiler being installed (set up) in your property by an expert engineer. 

Here at iHeat, we want to remove all of this undue stress and make the decision making process of upgrading to a new central heating system, as easy as possible.

Boiler costs can vary depending on a number of factors including their brand, model, fuel, output, warranty, labour and installation type. Typically a new boiler will cost between £1,845 and £3,500, below is a list of average boiler installations offered by iHeat (guide only).

Installation Type

Price (inc VAT)

Combi to combi swap


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System to combi conversion


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New boiler install


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Back boiler to a combi


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System to system


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Frequently Asked Questions

Why is My Boiler Working But No Hot Water?

If your boiler is operating but not producing hot water, this could be due to a malfunctioning diverter valve, which is responsible for directing hot water to either the heating system or to your taps. It's possible the valve is stuck or has failed. Additionally, the issue could be related to the thermostat not signaling the boiler to heat water, or the system may be experiencing low pressure which affects its ability to function properly.

Why Would I Suddenly Have No Hot Water?

A sudden loss of hot water can be caused by several factors. If you have a gas boiler, an interruption in the gas supply could stop the boiler from heating water. For electric boilers, a tripped electrical circuit could cut power to the unit. Mechanical failures within the boiler itself, such as issues with the heating element or burner, can also prevent hot water production.

Why is My Water Not as Hot from a Combi Boiler?

Combi boilers may not provide sufficiently hot water if the demand is too high, such as when multiple taps or showers are in use simultaneously. Additionally, a build-up of sludge or scale in the system can reduce the boiler's efficiency and its ability to heat water effectively. It's also worth checking the thermostat settings to ensure they are set high enough to heat the water to the desired temperature.

Why is Hot Water Not Coming Out of My Tap?

If hot water isn't coming out of your tap, the problem might be localized to particular plumbing issues like a blocked or frozen pipe, especially if only one tap is affected. Alternatively, if your system includes a mixing valve and it fails, this can prevent hot water from being properly mixed and delivered to your taps. Issues with separate water heaters, if used, can also disrupt hot water supply.

Why is My Hot Water Not Working But My Cold Water Is?

When hot water isn't working, but cold water is, the issue typically lies within the heating system rather than the water supply. Problems could include a malfunctioning water heater, incorrect settings or failures of the hot water thermostat, or issues with the boiler's diverter valve not directing heat to the water.

Why is My Hot Water Cold?

Cold water coming from the hot water tap is often due to failures in the heating system. In electric water heaters, the heating element might have burned out. For gas boilers, the pilot light might have gone out, or a safety mechanism like the thermal switch may have been triggered, cutting off the heat source.

How Long Does It Take for Hot Water to Come Back?

The time required for hot water to return can vary depending on the type of water heater you have. Tankless heaters typically provide hot water almost instantaneously, while traditional tank water heaters need time to heat a new tank of water once the existing supply has been depleted. The boiler's recovery rate also plays a role; combi boilers can heat water quickly but may struggle to meet high simultaneous demands. The size of your water heater's tank will also impact how quickly it can deliver hot water after being depleted.

Stephen Day profile photo
Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.