No Hot Water But Heating Works in Accrington - What to Check First

Published September 2026 | No Hot Water But Heating Works What to Check

Your radiators are warm, the boiler sounds like it's firing normally, but every tap in the house runs cold. Before you call anyone or start worrying about the cost of a repair, there's a real decision to make: do you run through a few checks yourself first, or do you pick up the phone straight away and book a Gas Safe engineer?

It's not a trivial choice. Some "no hot water" faults take ten minutes and cost nothing to fix. Others are caused by a failed internal component that's firmly in engineer territory - and poking around without the right knowledge can make things worse. Getting that boundary right is what this guide is for.

Option A - Running the Safe DIY Checks Yourself

DIY diagnostic checks are exactly that: diagnostic. You're looking for obvious causes that don't involve touching gas pipework, removing boiler covers, or adjusting components that need specialist tools. The good news is that a meaningful number of "heating works, no hot water" faults do have a simple settings or pressure cause that any homeowner can deal with themselves.

What This Involves

Work through these checks in order before assuming anything mechanical has failed. Our engineers find that a significant proportion of no-hot-water calls - particularly during the autumn when people are firing the heating up again after summer - turn out to have a control or settings cause.

1. Check your programmer or timer settings. If you've had a power cut recently, your boiler's programmer may have reset itself. Check that the hot water schedule is active and that the clock is showing the right time. This catches more faults than you'd expect.
2. Check the hot water thermostat on your cylinder. On systems with a separate hot water cylinder, there's usually a dial-type thermostat fitted directly to the cylinder. If it's been knocked or turned down accidentally during other work, the cylinder won't heat. Set it to between 60 and 65 degrees Celsius.
3. Check the boiler pressure gauge. Most modern combi boilers - Baxi, Worcester Bosch, Vaillant, Ideal - have a pressure gauge on the front panel. If it reads below 1 bar, low pressure may be preventing the hot water circuit from operating correctly. You can re-pressurise using the filling loop; your boiler manual will have the specific steps for your model.
4. Look for a fault code on the boiler display. Most boilers made in the last fifteen years display an error code when a fault is detected. Note the code and look it up in your manual or on the manufacturer's website. This tells you whether the fault is a settings issue or something mechanical.
5. Check if an immersion heater is fitted. If your hot water cylinder has an electric immersion heater as a backup, switching it on can restore hot water temporarily while you sort out the boiler fault - useful if you've got people in the house who need a shower.
6. Use the Voltrade GoFIX diagnostic tool. If you're unsure what a fault code means or want help cross-referencing what you've found, the GoFIX tool walks you through the most common boiler faults and their likely causes. It helps you arrive at an appointment with a much clearer picture of what's needed, which can speed up the repair.

Pros of Checking Yourself First

Cost is the obvious one. These checks are free and take fifteen to twenty minutes at most. If the fault is a reset programmer or low boiler pressure, you've avoided a call-out fee entirely. Getting a boiler engineer out to Accrington on short notice during colder months typically costs between 60 and 120 pounds for the call-out alone - before any repair work begins.

Running through these checks also arms you with useful information before you speak to an engineer. You can tell them exactly what you've already ruled out, which speeds up their diagnosis and reduces the time they spend on site.

Cons and Limitations

DIY checks have a hard ceiling. Once you've ruled out settings, pressure, and timer causes, you're into component territory - diverter valves, thermistors, motorised valves, plate heat exchangers - and touching these yourself is not only technically difficult but legally problematic if it involves gas components. You also risk making the fault worse, or voiding your boiler warranty if it's still active. If the basic checks don't turn anything up, stop there.

Option B - Booking a Gas Safe Registered Engineer

What a Gas Safe Engineer Will Actually Do

A competent engineer will arrive with diagnostic equipment and hands-on knowledge of the most common fault patterns for your boiler make and model. For a "heating works, no hot water" complaint, the investigation typically follows this sequence:

1. Confirm the symptom and eliminate the obvious. They'll check programmer and thermostat settings first - not because they don't trust your checks, but because it's the quickest thing to eliminate and occasionally something gets missed.
2. Check temperatures at key points in the system. Using temperature probes, they'll measure how hot the flow and return pipes are and whether heat is actually reaching the hot water circuit.
3. Test the diverter valve. On a combi boiler, this is the most common cause of the exact fault you're describing. The diverter valve switches the boiler's output between the central heating circuit and the hot water circuit. When it sticks or fails, it commonly stays locked in heating mode. The engineer will test whether it's moving correctly and sealing properly.
4. Test the thermistor and sensors. The thermistor is a temperature sensor that tells the control board what temperature the water has reached. If it's giving false readings, the boiler may believe the hot water is up to temperature when it isn't. Electrical tests confirm whether the sensor is accurate.
5. Check the plate heat exchanger on combi boilers. In areas with harder water - and parts of Lancashire do have relatively hard water - scale can build up inside the plate heat exchanger over time, restricting heat transfer. This is a less obvious cause but a real one, particularly in boilers that haven't been serviced regularly.
6. Check the motorised valve on conventional systems. If the valve that directs heated water to the hot water cylinder has a failed motor or is mechanically stuck, the cylinder won't heat even though the central heating runs perfectly.

What Repairs Typically Cost in 2026

Costs vary depending on the fault and the parts needed. Based on current UK pricing:

• Diverter valve replacement: typically 150 to 300 pounds including parts and labour
• Thermistor replacement: typically 80 to 150 pounds
• Motorised valve replacement: typically 100 to 200 pounds
• Plate heat exchanger replacement: typically 200 to 400 pounds - one of the more involved combi boiler repairs
• Call-out and diagnostic visit (no repair completed that day): typically 60 to 120 pounds in Accrington and the surrounding area

Pros of Calling an Engineer

The main advantage is that they can actually fix the problem. Most engineers carry common parts - diverter valves and thermistors for popular brands like Worcester Bosch, Vaillant, and Baxi are standard van stock - which means same-day repair is often possible when the fault is one of the usual suspects. You'll also receive a Gas Safe certificate for any work carried out on gas components, which matters for insurance purposes and when you eventually sell the property.

Cons to Bear in Mind

Cost is the obvious factor, particularly if the repair turns out to involve a major component. There can also be a wait for an appointment, though many engineers covering Accrington offer same-day or next-day slots for heating and hot water faults. If your boiler is twelve to fifteen years old and the repair estimate is significant, it's worth having an honest conversation about whether repair still makes sense against replacement.

Side-by-Side Comparison

Which Is Right for Your Situation

The answer typically comes down to how suddenly the fault appeared and whether you've already spotted any obvious causes.

Start with DIY checks if the no-hot-water fault appeared after a power cut, after someone has been adjusting the programmer or thermostat, or if the boiler's pressure gauge is sitting below 1 bar. These are quick to address and cost nothing to rule out. If the fault appeared gradually - intermittent hot water that eventually stopped altogether - that pattern commonly points to a failing component rather than a settings issue, and booking an engineer from the start is the sensible call.

If you have a Worcester Bosch Greenstar, a Vaillant ecoTEC, or a Baxi Platinum - all very common in Accrington - and you can see a fault code on the display, look it up before calling. Codes that translate to diverter valve or NTC thermistor faults tell you straight away that you need a Gas Safe engineer, and you can pass that information on when you book.

If your boiler is still under the manufacturer's warranty, check the terms before attempting anything beyond the most basic controls checks. Some warranties are voided by any adjustment outside what's outlined in the user manual.

What Accrington Homeowners Typically Choose and Why

In our engineers' experience across Accrington and the wider Lancashire area, most homeowners take a sensible middle path: they run through the basic controls checks themselves, find nothing obvious, and then call an engineer. That's generally the right approach - it's quick to attempt, costs nothing, and gives you useful information before you make the call.

The housing stock in Accrington is a real mix. Older terraced properties often have conventional boilers with a separate hot water cylinder, where a failed motorised valve is a common culprit. Newer builds tend to have modern combi boilers - Worcester Bosch, Vaillant, and Baxi dominate - where a stuck diverter valve is by far the most frequently diagnosed cause of this particular fault. Knowing which type of system you have helps narrow things down before you speak to anyone.

One pattern our engineers see regularly: homeowners who've had the fault for a week or more before calling tend to end up with a more complicated repair. A diverter valve that's been partially working - giving you hot water sometimes but not reliably - can cause secondary issues if it's left. The sooner you get it looked at once the basic checks haven't helped, the better.

Lancashire's water hardness also plays a role that some homeowners don't factor in. Scaling inside the plate heat exchanger is more common than you might expect in this region, and it's one of the reasons annual servicing with a system check matters - it catches build-up before it becomes a fault.

Making Your Decision

Has the boiler pressure dropped below 1 bar?

If the pressure gauge is reading low, re-pressurise using the filling loop before doing anything else. Low pressure is one of the most common reasons a combi boiler fails to produce hot water even when the heating appears to work. Most boiler manuals include step-by-step instructions for this and it takes about five minutes. If the pressure drops again within a day or two of topping it up, that suggests a system leak or a faulty pressure relief valve, and you'll need an engineer to locate and fix the source.

Is there a fault code showing on the boiler display?

Look the code up before calling anyone. A fault code pointing to a diverter valve, thermistor, or heat exchanger tells you clearly that you need a Gas Safe engineer, and you can relay that information when you book - which helps the engineer arrive with the right parts. Codes relating to ignition or water pressure give the engineer useful context about whether there's a wider issue alongside the hot water fault.

How old is your boiler?

If your boiler is more than twelve years old and the repair estimate is coming in above 300 pounds, it's worth asking the engineer directly whether repair still makes sense. A replacement A-rated combi boiler typically costs between 1,800 and 3,500 pounds installed in the Accrington area, depending on boiler brand and the complexity of the job. Modern boilers are considerably more efficient than older models, and the running cost savings can meaningfully offset the upfront cost over a few years. An engineer giving you an honest assessment will lay that comparison out clearly rather than just pushing whichever option earns them more.

When was your boiler last serviced?

Annual servicing is the single most effective thing you can do to avoid faults like this one. A service catches developing problems before they become complete failures, checks that all components are operating correctly, and in Lancashire's harder water areas, gives an engineer the chance to flag any scaling that's starting to build up. If you can't remember the last service date, tell the engineer when you call - it's useful context for their diagnosis, and if the system hasn't been touched in a few years, a power flush may also be recommended to clear any build-up in the pipework.

Frequently Asked Questions

Why does my heating work but I have no hot water?

On a combi boiler, this is most commonly caused by a faulty diverter valve - the component that switches heat output between the central heating circuit and the hot water circuit. When it sticks in heating mode, your radiators work but your taps run cold. Other common causes include a failed thermistor, a scaled-up plate heat exchanger, or on systems with a separate hot water cylinder, a faulty motorised valve that's preventing the cylinder from heating.

Can I fix no hot water myself or do I need a Gas Safe engineer?

How much does it typically cost to fix no hot water on a combi boiler?

It depends on the fault. A diverter valve replacement commonly costs between 150 and 300 pounds including parts and labour. A thermistor replacement typically runs to 80 to 150 pounds. A plate heat exchanger replacement - one of the more involved repairs - can reach 200 to 400 pounds. Call-out and diagnostic fees for engineers covering Accrington and the surrounding Lancashire area typically sit between 60 and 120 pounds.

How long does a boiler repair for no hot water usually take?

Most common component replacements - diverter valves, thermistors, motorised valves - can be completed in one to two hours if the engineer has the relevant part on the van. For less common components or older boilers where parts need to be ordered, a return visit is usually arranged within a few days. In most cases, you should have hot water restored either the same day or the day after the engineer's first visit.