No Hot Water from Boiler

Common Reasons Why & How to Fix It

No Hot Water From Boiler

Found yourself with no hot water? Follow our ultimate troubleshooting guide before calling out an engineer, to help you get to the bottom of this!

Found yourself with no hot water? The last thing you want this time of year is a cold shower or a freezing bath.

Follow our ultimate troubleshooting guide before calling out an engineer, to help you get to the bottom of this.

We will kick off our troubleshooting guide with some first steps to take, to ensure there’s not a quick fix to your hot water troubles.

Step 1: First, easy checks

Hit the reset button

Most boiler models come with a manual reset button, while some do it automatically when they encounter an issue.

Try doing a manual reset or by switching your boiler off and on again, before anything else. You can even do this at the mains to be sure. It may rectify the problem.

Check your supplies

Whether your boiler is gas or electric, you should ensure your boiler is getting enough of what it needs in order to work.

Check your water too at this stage. Whether it is a local/area problem, like a power cut, or something you may have accidentally done yourself – it will be an unnecessary cost to call an emergency engineer out.

The same goes, particularly with gas boilers. If your other gas appliances aren’t working either, it’s more likely there is a problem with your gas supplier/supply, not your boiler or hot water.


If there has been a power cut, it is not unusual for boilers to reset to a default mode or factory settings which may stop your boiler from functioning in the way you’d expect.

Other settings can wreak havoc with your boiler and fixing them won’t require the help of an engineer.

That’s why we suggest you check your thermostat to ensure the dial hasn’t been knocked or changed accidentally.

Similarly, have the clocks gone back or forward and you’ve forgotten to change a timer? It may sound like an obvious answer, but you’d be surprised how many people get caught out.

Step 2: Common troubleshoot solutions for no hot water

Weather issues/frozen pipes

In harsh winters or prolonged cold environments, pipes can easily freeze. Typically, it is the condensate pipe which can freeze because it is connected to the outdoors of your house.

Two solutions can be either:

a. wait for the pipe to defrost by itself or

b. pour very warm water over your pipe. Don’t use boiling water in case you cause damage. Now fire up your boiler.

Try this a few times before you call an engineer as it can take multiple efforts to thaw your pipes before it works.

Diverter Valves

If your home’s central heating is still working and it is just the fact there is no hot water being produced, then this is usually indicative of problems with a diverter valve.

This valve’s job is to allow combi boilers to go from heating radiators to heat your hot water once you’ve turned a tap on.

If you have no hot water, your diverter valve may be at fault or stuck on central heating.

No hot water due to air in pipes

Sometimes if you have no hot water, or your hot water is coming out in an inconsistent, spluttering manner this is most commonly associated with airlocks in pipes.

When air is trapped in pipes, it stops the water coming out smoothly, if at all, and behaves like any other blockage.

Removing airlocks can be done by attaching a hosepipe to the tap that isn’t working (in this case, a hot tap). Then fit the hosepipe’s other end to a working (in this case, cold) tap. Turn the hot tap on, followed by the cold tap.

The mains water pressure will push airlocks out. Leave the taps running to ensure it works and then carefully remove the hose from the lower tap (to avoid creating more airlocks/vacuum. Try this again, if it doesn’t work at first.

No hot water due to low pressure

This can be a common problem for owners of combi boilers or sealed systems. You can check your hot water pressure from time to time. The pressure gauge should be around 1 bar or check an indicator needle (if one is present) for an idea on how the pressure should be.

In order to add pressure, you can check that there aren’t any leaks anywhere in your system, as this is a common cause for drops in pressure.

You can also manually re-pressure your boiler but make sure you check your boiler’s manual first. Be aware, if instructions ask you to remove your boiler panel, we recommend you call an engineer.

Recommended reading: What Should Boiler Pressure Be When Heating Is On

Read our guide on how to re-pressurise your boiler below.

Open vented boilers/stuck ball valve float

Unlike combi boilers and sealed systems, an open vented boiler will have a water tank usually located in the loft.

A ball valve float’s job is to detect water levels and control flow. Ball valve floats can get stuck and prevent any water circulating through the system.

If you can see into the tank, check that the ball float valve is not stuck, then see if you can gently free the ball and see if water begins flowing again.

No hot water in the shower ONLY

In this more specific example, you may be getting hot water from your taps, but not in your shower. If this is happening, it is most likely down to another valve, known as the “mixing valve.”

If this becomes stuck or is faulty, it will need to be replaced. This is not a costly procedure. If you have just moved in somewhere new and there is a new shower, the built-in anti-scalding device may have been set too high, so the water is not being allowed to heat up enough.

You can usually locate the anti-scalding device behind the tap/knob/switch which changes the heat of the shower.

Step 3: No hot water in gas boilers

Gas boilers can cause a number of problems, many of which we can provide a solution.

However, we highly recommend you call for a Gas Safe registered engineer first, or if you think you can provide a solution yourself, that you first remove any members of your family or people in the business out of the building, to really minimalise the impact of any risks.

When dealing with gas, safety should always be at the forefront of what you do, as the repercussions can be deadly.

Next, you should check if any of these troubleshooting questions can help you…

Can you see the pilot light/flame on?

If your gas boiler’s pilot light has gone out, your boiler will have no way of igniting any gas that is being released by the system.

Without any chemical reactions/ignition of gas, there cannot be any production of heat.

However, a simple solution is you need to check there is no reason for your pilot light to go out repeatedly and relight it safely.

A manual reigniting of a gas boiler’s pilot light could help if you have no hot water. If issues with your pilot light continue, call a PHS Gas Safe engineer as soon as possible.

Can you smell gas?

If you can ever smell gas, exit yourself and others from the building immediately.

Notify your local gas provider and even the emergency services if you are not sure what else to do.

Most importantly, do not re-enter the property.

Have you got a leak?

Any leak will cause a boiler to drop in pressure and that could easily lead to no hot water as well as causing issues with your building’s structure through damp etc.

If a lot of cold water goes into the tank, more condensation will be produced, so firstly, ensure you are not mistaking a leak for condensation. Once the heating comes on, this will dry up and be nothing to worry about.

If however, you continue to have no hot water, and you suspect there is a boiler water leak, be careful before you touch anything.

Scalding hot water could be dripping/leaking out of your system, just as likely as cold water could, so do not presume the water will be cold.

Where to check for a leak?

If you haven’t seen any definite signs of a leak but think there could be one, here are our top places to check.

In these areas check for drips, anything that needs retightening, clearing up of any debris/sediment build up.

  1. The drain valve – head to the bottom of your hot water tank.
  2. Spigot – do valves need replacing?
  3. Tank – whatever the size, this can cause huge amounts of damage and is not something to be ignored.

In almost every case you will need assistance from a plumbing engineer when it comes to leaks. A small error could result in worsening your own situation or causing a lot of mess.

If you think you may have a leak but cannot locate it, speak to our engineers at PHS who are specially trained in water leak detection and repair in commercial and residential environments.

Pressure and valves

We’ve mentioned pressure and valves a lot throughout the troubleshooting guide and that’s because these are two crucial elements.

Pressure relief valves stop your boiler from exploding under too much pressure or failing under too low pressure.

Faulty pressure relief valves will allow the pressure to drop to such an extent you can end up with no hot water and this can be dangerous.

Replacing a valve yourself can be done, just ensure you pay close attention to the manufacturers’ guide.

Due to the fact this process involves part draining the tank as well as the replacement of the valves, you may need assistance from an engineer.

Recommended reading: How to Drain a Central Heating System

Step 4: No hot water in electric boilers

Many of the problems you encounter with gas boilers, you will not encounter with an electric one.

While they are more reliable than gas boilers, they are not always perfect so from time to time electric boiler users can find themselves with no hot water.

Recommended reading: Electric Central Heating Boiler vs Gas Boiler: Pros & Cons

Due to the nature of electric boilers and the fact they are supplied by high voltage electricity the risks can be just as dangerous, if not more so, than gas boilers.

What you need:

To work on these types of boilers you must ensure you are capable of doing so. Ensure there is not a general problem with power in the house or area first.

Reset your fuse box if necessary and see if your boiler returns to normal. If it doesn’t, before starting work, you must turn the power off to your boiler.

Next, ensure you have the right electricity testing tools to help you do the job safely.

Do not attempt to work with electricity if you are not confident using testing tools like this.

Elements to check:


Thermostats can be hard to locate, so consult your manufacturer’s guide to be sure. If you can confidently access the thermostat, we recommend you revert the entire thing to its factory settings.

If you accidentally set the temperature too high you could end up causing dangerously high water temperatures which in turn can cause burns.

Circuit breaker

If your fuse has blown or the circuit has tripped, you can usually just replace the fuse or reset the circuit breaker. If your boiler continues to trip you will need an electrician.

Heating elements

Depending on the model of your electric boiler, you will have one, two or even more heating elements. Check these elements using any tool that detects voltage.

Usually, there will be one place in the upper end and this heating element has a knock on effect to the lower one.

If you have no hot water at all, this will be indicative of the thermostat problems mentioned above, or a problem with the “upper” element.I

f your lower element breaks, you should be able to still get a bit of hot water.

Check both elements with your element tester, in order to be sure and also make sure they are grounded.

Step 5: Final notes

In this next section, we cover a few more things to consider and a quick how-to, if you’re considering manually re-pressurising your boiler (as mentioned in the second step earlier in this guide).

How to re-pressurise your boiler

If your manual is clear that this is something you can do on your own, then we can give you a walkthrough on how to do it. If you do not feel comfortable, an engineer from PHS can be with you soon to help.

  1. Locate the “boiler filling loop” and “pressure gauge.”
  2. Ensure you know what pressure you are aiming for: operating pressure system is between 1-1.5 bar – but your manual should provide clarity on this for your particular model. Otherwise, a green area can sometimes be the indicator for this on the pressure gauge itself.
  3. Turn the system off.
  4. Turn both of the filling loop handles so that they are going in the same direction of the pipe. Do not be concerned if you hear the flow of water at this point. This is perfectly normal.
  5. Watch the gauge as you do this and move slowly so you don’t suddenly over-pressurise the boiler.
  6. Once you have reached the ideal pressure, close the handles.

Is your boiler big enough?

If your boiler has been working fine for months/years and this has never been a problem, then this won’t apply to you.

However, if you’ve just moved in, got a new boiler or increased your water usage lately and be suffering from no hot water regularly, this may be the reason for your troubles.

Your boiler can sometimes just not be keeping up with demand and if your house is big or you’re using a lot of hot water, it may be time to upgrade to a larger boiler.

Call a member of the PHS team today to discuss your options and see if you have the wrong type of boiler for your property.

Is your tank big enough?

Similarly, if your tank isn’t big enough then it won’t be able to hold enough water and it won’t be keeping up with demand.

This is only relevant to properties which have a tank to start with! Many smaller properties do not require a tank, at all.

Is your boiler due to routine works or a service?

Always try to keep on top of routine works when it comes to boilers and then you should hopefully be less likely to run into any unexpected errors.

We recommend once a year and if you have a new boiler this is a must to ensure you don’t void your warranty.

While a service might not fix your issues, they could prevent them from happening in the future.

Step 6: Don’t hesitate to get in touch

At PHS we have Gas Safe engineers who are trained to troubleshoot issues like this as well as provide general central heating services, maintenance and boiler repairs.

If you have followed this guide and you are still not sure on a solution, or if you would like to talk through a solution with us, give us a call.

Our engineers are exceptionally well trained, providing fixes on the first visit and available to you 24 hours a day.