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

Published October 2026 | No hot water but heating works what to check

If you can smell gas at any point while investigating this problem, stop immediately. Open windows, leave the property, and call the National Gas Emergency Service on 0800 111 999.

Your radiators are warm, the thermostat is doing its job, but every hot tap in the house runs cold. It's a frustrating situation, and one our engineers in Basildon deal with regularly. The reason this happens is that heating and hot water are often controlled by separate components within your boiler system - so one can fail while the other keeps running. Knowing which part has given up tells you how urgent this is and what it's going to cost to fix.

Immediate Actions - Do These NOW

Before you call anyone out, work through these checks in order. Some of them will fix the problem without any engineer involvement at all.

1. Check your programmer and hot water schedule

This sounds too simple to be the cause, but it's responsible for more call-outs than most people realise. Your boiler programmer typically has separate schedules for heating and hot water. If the hot water programme was accidentally cleared - after a power cut, a battery change, or someone pressing the wrong button - the system will happily run your radiators while blocking hot water entirely. On Worcester Bosch, Vaillant, and Ideal boilers, look for a dedicated "hot water" or "DHW" (domestic hot water) setting and confirm it's active and scheduled for the right times.

2. Check your boiler pressure

Find the pressure gauge on the front of your boiler. It should sit between 1 and 1.5 bar when the system is cold. A reading below 1 bar can interfere with how the boiler manages hot water delivery. You can repressurise using the filling loop - usually a flexible braided hose underneath the boiler unit. Check your boiler manual for the exact process, or use the Voltrade GoFIX diagnostic tool online for a step-by-step walkthrough matched to your specific model.

3. Inspect your hot water cylinder if you have one

Many Essex homes - particularly those in Basildon built before the 1990s - have a system or regular boiler paired with a hot water storage cylinder rather than a modern combi unit. If your home has a cylinder, check the cylinder thermostat. It should be set between 60 and 65 degrees Celsius. Also feel the side of the cylinder with your hand. If it's completely cold, the motorised valve, cylinder thermostat, or immersion heater may have failed independently of the boiler itself.

4. Try a boiler reset

Many boilers - including popular models from Baxi, Vaillant, and Worcester Bosch - can lock out in a way that affects only the hot water circuit while leaving heating intact. There's usually a reset button on the front of the unit. Press and hold it for a few seconds, wait for the boiler to fire back up, then test your hot taps. If hot water returns and stays on, you've cleared a temporary fault. If the boiler locks out again within a few hours, there's an underlying issue that needs proper diagnosis from an engineer.

What NOT to Do

When you're stuck with cold water, it's tempting to start experimenting. Some common instincts are actually counterproductive or outright dangerous.

Don't open the boiler casing. Working inside a gas boiler without being Gas Safe registered is illegal in the UK. It's also dangerous. Gas boilers contain pressurised water circuits, live electrical connections, and gas pipework - none of which should be touched by anyone other than a registered engineer, regardless of how minor the visible fault appears.

Don't keep resetting a boiler that keeps locking out. If you've reset the boiler twice and it's faulting again, you need an engineer - not another reset. Repeated lockouts put sustained stress on the heat exchanger and other internal components, and can turn a 200-pound repair into a significantly more expensive one.

Don't crank everything up to maximum. Turning the thermostat or programmer to its highest setting won't fix a failed diverter valve or a faulty thermistor. It just burns extra gas and puts unnecessary load on the system while the underlying fault remains unresolved.

Don't leave a leaking boiler running. If you notice water dripping from the boiler unit alongside the hot water loss, switch the boiler off at the isolator and call an engineer promptly. A leak points to a more serious internal fault that won't get better on its own.

When This Is a Genuine Emergency vs When It Can Wait

Not every case of no hot water requires an emergency call-out. Here's how to assess the urgency of your situation .

It can wait a day or two if:

• Your hot water cylinder has an immersion heater you can switch on as a temporary measure
• The problem appears related to programmer settings or a one-off lockout rather than a mechanical fault
• Everyone in the household is healthy and there's no welfare concern
• The boiler is running without error codes or fault lights

Call an engineer the same day if:

• You have young children, elderly residents, or anyone with a medical condition at home
• Temperatures in Essex are dropping and the forecast is cold overnight
• The boiler is displaying a fault code you don't recognise
• Hot water has been completely absent for more than 24 hours

Treat it as an emergency right now if:

• You can smell gas anywhere near the boiler or anywhere in the property - call 0800 111 999 immediately
• Water is actively leaking from the boiler unit
• The boiler is making loud banging, hissing, or gurgling sounds alongside the hot water loss

As detailed by boiler repair specialists, the most common causes when heating works but hot water doesn't vary significantly depending on whether you have a combi boiler or a cylinder-based system - so identifying your boiler type is an important first step before calling anyone out.

Getting Emergency Help in Basildon

If you've worked through the checks above and still have cold taps, you need a Gas Safe registered engineer. Gas Safe registration is a legal requirement in the UK for anyone working on gas appliances - not a preference, a legal obligation. Always ask to see the engineer's Gas Safe ID card before work begins, and verify it at the Gas Safe Register website if you're in any doubt.

For Basildon homeowners, same-day appointments are typically available for complete hot water failure, particularly through the winter months when systems are under sustained load and demand rises. When you book, have the following ready so the engineer can arrive prepared:

• Your boiler make and model - usually on a label or sticker on the front of the unit
• Any fault codes or warning lights currently displayed
• Whether you have a combi boiler or a system with a separate hot water cylinder
• How long you've been without hot water and whether it was sudden or gradual

Arriving with the right parts for the most likely fault cuts the repair time significantly, and in most cases means hot water is restored in a single visit rather than two.

What the Emergency Repair Involves

The actual repair depends on which component has failed. Here's what our engineers find most commonly, and what it typically costs in the current UK market.

Diverter valve replacement. This is the most frequently diagnosed cause of heating-works-but-no-hot-water on combi boilers. The diverter valve is a mechanical component that directs water flow between the central heating circuit and the domestic hot water circuit. When its internal seals degrade or the valve sticks open, the system defaults to heating mode and leaves hot water supply cut off. On most combi boilers - including Worcester Bosch, Ideal, and Baxi models - diverter valve replacement typically costs between 200 and 400 pounds including parts and labour, depending on the boiler model and how accessible the component is.

Thermistor replacement. The thermistor is a temperature sensor that monitors water temperature inside the boiler. If it reads incorrectly, the boiler may conclude that the hot water has already reached its target temperature and stop heating it - even while cold water comes out of your taps. This tends to be a quicker fix, commonly costing between 100 and 200 pounds.

Motorised valve repair or replacement. In Basildon properties with older system or regular boilers, the mid-position or two-port motorised valve is a common failure point. This valve controls whether hot water is directed to the cylinder or the radiators. When it fails, the cylinder simply doesn't get the heat it needs. Replacement parts and labour typically come to between 150 and 300 pounds depending on the valve type and access.

Programmer or controls fault. Sometimes the issue sits entirely in the controls rather than the boiler itself. A failed timer, a wiring fault, or a broken zone valve controller can isolate the hot water circuit from the rest of the system while leaving heating unaffected. This is usually the least expensive fix, commonly between 80 and 150 pounds.

Our engineers use the Voltrade GoFIX diagnostic process before quoting on any repair. This structured approach identifies the specific fault rather than replacing parts speculatively, which keeps costs down and gets you back to hot water faster.

Frequently Asked Questions

Why does my heating work but not my hot water?

On a combi boiler, a stuck or failed diverter valve is the most common cause. This component switches water between the heating circuit and your hot taps - when it fails, it typically defaults to heating mode and blocks hot water. On system boilers with a cylinder, a faulty motorised valve or failed cylinder thermostat is more likely. There are typically nine distinct causes depending on your boiler type, and a Gas Safe registered engineer can diagnose the exact fault on the same visit.

Can I fix a diverter valve myself?

No. Replacing a diverter valve means opening the boiler casing and working with internal components connected to the gas supply and pressurised water circuit. In the UK, this work is legally restricted to Gas Safe registered engineers - attempting it without registration is illegal, dangerous, and will void any remaining manufacturer warranty on the boiler. If you're in Basildon and suspect a diverter valve fault, book a registered engineer for a same-day diagnosis.

How long does a boiler hot water repair take in Essex?

Most common faults - including diverter valve replacement and thermistor swaps - can typically be completed within one to two hours once the engineer is on site, provided the right parts are available. More complex repairs on older systems, or situations where a specific part needs to be ordered, may require a return visit the following day. In the majority of cases, hot water is restored on the same day as the initial call-out.