No Hot Water But Heating Works in Manchester? Most Likely a Diverter Valve | Next Gen Boilers
Quick Answer
Why do I have heating but no hot water?
On a combi boiler, this is almost always caused by a faulty diverter valve — the component that switches the boiler between heating mode and hot water mode. It's usually stuck in heating mode, supplying radiators but not the taps.
You turn on the tap expecting hot water — but nothing comes. Yet your radiators are warm and your heating system seems to be working perfectly. This specific combination of symptoms is one of the most common boiler faults our engineers are called out to across Manchester and Salford, and in the vast majority of cases it has one cause: a faulty diverter valve.
What Is the Diverter Valve?
Combi boilers (combination boilers) — the most common type in Manchester homes — produce both heating and domestic hot water from a single unit. When you turn on a hot tap, the diverter valve switches the boiler from heating mode to hot water mode, diverting the hot water from the radiator circuit to the hot water circuit.
When the diverter valve fails, it often gets stuck — either partially or fully in heating mode. This means the boiler continues heating the radiators normally, but hot water requests from the taps are not being fulfilled. You get perfect heating but no hot water.
Signs of a Diverter Valve Fault
The classic sign is exactly as described — heating works but the hot water taps run cold. You might also notice that you get a brief burst of hot water when you first turn on a tap (while the valve switches) but it quickly goes cold, or that hot water only works when the heating is turned off.
Some diverter valves fail gradually — you might first notice the hot water taking longer to come through, or the temperature being inconsistent, before it stops working entirely.
Other Possible Causes
While the diverter valve is the most common cause, there are other possibilities worth checking. A faulty thermistor (temperature sensor) can prevent the boiler from switching modes correctly. On some boilers, a failed PCB can cause the same symptoms. And on older system boilers (rather than combi boilers) with a hot water cylinder, the problem is more likely to be a failed motorised zone valve, immersion heater element or cylinder thermostat.
Our engineers will carry out a full diagnosis to confirm the exact cause before quoting for any repair.
How Much Does a Diverter Valve Repair Cost?
Diverter valve replacement in Manchester typically costs £200–£350 including parts and labour, depending on the boiler make and model. Worcester Bosch and Baxi diverter valves are usually the most straightforward to source and replace. Some older or discontinued models can take longer to source parts for.
In some cases, if the boiler is old and the diverter valve repair cost is approaching 30–50% of the value of a new boiler, we'll recommend considering a replacement — particularly if other components are also showing their age. We'll always give you an honest assessment.
Frequently Asked Questions
Can I fix a diverter valve myself?
No. Replacing a diverter valve requires draining the system, accessing internal boiler components and working with gas — this must be done by a Gas Safe registered engineer.
How long does a diverter valve replacement take?
Typically 1–2 hours for a straightforward replacement. Our engineers carry common diverter valve parts on the van for popular boiler models, so it can often be completed in a single visit.
Is it worth repairing a diverter valve on an old boiler?
If the boiler is under 10 years old and otherwise in good condition, yes. If it's older and already had several repairs, the cost might be better put toward a new boiler installation — which comes with a 10-year warranty and much lower running costs.
My hot water worked for a few minutes then went cold — is this a diverter valve fault?
Possibly — this intermittent failure pattern can indicate a diverter valve that's failing but not completely stuck yet. It's worth getting it looked at before it fails completely.
Can a boiler service fix a diverter valve fault?
An annual service can identify wear in the diverter valve before it fails completely, but once failed, the valve needs to be replaced rather than serviced.
Need emergency boiler help in Manchester or Salford? Call: 07305 687 331