No Hot Water in the Shower but Taps Are Fine? Causes and Fixes
Shower running cold or only lukewarm while the hot taps work? How to tell whether it is the shower valve, the cartridge, an electric shower, a pump or the hot water supply, and what each fix involves.
If the hot taps work but the shower runs cold, the fault is almost always in the shower itself rather than the boiler. On a mixer shower the usual cause is a worn or scaled-up thermostatic cartridge, or a maximum temperature stop that has slipped. On an electric shower it is usually the heating element, a thermal cut-out or low water flow. If the hot taps are cold as well, the problem is your hot water supply, such as the boiler or cylinder, not the shower.
Key Takeaways
- Run a hot tap first. If the taps are hot and only the shower is cold, the shower is the problem.
- Mixer showers usually fail at the thermostatic cartridge, especially in hard-water areas like most of London.
- Electric showers heat their own water, so a cold electric shower is an element, cut-out or flow problem, not a boiler one.
- A shower that goes hot then cold can be a combi boiler struggling with low flow, or another tap drawing water.
- Do not strip an electric shower yourself. Isolate it at the pull cord and get it checked.
If your shower is running cold but the hot taps work, the fault is in the shower, not the boiler. On a mixer or thermostatic shower the usual culprit is a worn or scaled-up cartridge, or a maximum temperature stop that has slipped. On an electric shower it is usually the heating element, a thermal cut-out or poor water flow. If the hot taps are cold as well, the problem is your hot water supply, and the shower is just where you noticed it.
First: are the hot taps working?
Before anything else, run the hot tap on the basin or kitchen sink for a minute. This one check tells you where to look.
- Taps hot, shower cold: the boiler or cylinder is making hot water. The fault is in the shower valve, the cartridge, or the electric shower unit.
- Taps cold too: the problem is the hot water supply. On a combi boiler see our guide to no hot water when the heating works. If you have a cylinder, check the immersion heater and the boiler timer, or read our guide to an unvented cylinder with no hot water.
- Taps lukewarm: the hot water is being made but not hot enough. That points to boiler settings, a cylinder thermostat or a cylinder that is running out.
What type of shower do you have?
The fix depends on how your shower gets its hot water. Most London homes have one of these:
| Shower type | How to recognise it | Where the hot water comes from |
|---|---|---|
| Thermostatic mixer | Bar valve on the wall or concealed controls, usually one knob for temperature and one for flow | Your boiler or cylinder |
| Manual mixer | Single lever or knob that mixes hot and cold, no temperature numbers | Your boiler or cylinder |
| Electric shower | A plastic box on the wall with its own controls, a pull cord switch in the ceiling | Heated inside the unit from cold mains |
| Power shower or pumped mixer | A pump in the airing cupboard or loft, or a power shower unit on the wall | A gravity-fed cylinder, boosted by the pump |
Mixer and thermostatic showers
Thermostatic showers blend hot and cold water inside a cartridge that reacts to temperature. They are safer than manual mixers, but the cartridge is also the part that fails most. In hard-water areas, which covers most of London, limescale builds up in and around the cartridge until it cannot open far enough on the hot side.
Signs it is the cartridge
- The temperature knob turns but makes little difference.
- The shower is lukewarm at best, even on full.
- The temperature drifts during a shower.
- The shower is older and you have never had the cartridge changed.
Check the temperature stop
Most thermostatic showers have a safety stop, usually a button on the temperature knob, that stops you turning past around 38°C without pressing it. If the knob has been removed or has slipped on its spline, the stop can end up in the wrong place, limiting the shower to a cooler setting. Press the button and see if you can turn further. If the knob was recently taken off for cleaning, it may simply have gone back on in the wrong position.
Inlet filters
Many bar valves have small mesh filters where the hot and cold pipes connect. If the hot side filter is blocked with scale or debris, the valve gets mostly cold water. Cleaning them means isolating the water to the shower first, so if there are no isolation valves on the supply, leave it to a plumber.
We repair and replace thermostatic shower valves, including concealed ones, and can usually source cartridges for the common brands.
Electric showers
An electric shower heats cold mains water as it passes through, so your boiler has nothing to do with it. A cold electric shower is normally one of these:
- Heating element failed: the shower runs but the water never warms up, whatever the setting.
- Thermal cut-out tripped: a safety device that switches off the heating if the unit overheats, often because the flow is restricted.
- Low flow: a scaled-up shower head or kinked hose can cause overheating and cut-outs, and some units will not heat properly if the flow is too low.
- Power supply: a tripped circuit breaker, a faulty pull cord switch, or a problem with the shower's dedicated circuit.
You can safely clean the shower head and check the hose is not kinked. Anything inside the unit involves mains electricity and water together, so switch it off at the pull cord and have it checked. Old electric showers are often not worth repairing, and replacement is usually the better option.
Power showers and pumped systems
If your shower is fed by a pump from a hot water cylinder, a cold shower can mean the cylinder has run out, the cylinder thermostat is set too low, or the pump is only moving cold water because of an airlock on the hot side. A pump that runs noisily, surges, or starts and stops on its own is usually part of the story. Our guide to shower pump problems covers this in detail.
Shower goes hot then cold
A shower that starts hot and then goes cold, or keeps switching between the two, is a slightly different problem:
- Someone else is using water. A toilet flushing, a washing machine filling or a tap running can upset the balance, especially with a manual mixer.
- Combi boiler at low flow. If the shower is only drawing a little hot water, some combis struggle to keep the burner lit and switch on and off, so the water swings between hot and cold.
- Cylinder running out. A cylinder that is too small for the household, or has a faulty thermostat or immersion, will give you a few minutes of hot water and then run cold. See hot water running out quickly.
- Worn thermostatic cartridge. A cartridge that cannot react properly will overshoot and undershoot the temperature.
What a repair involves
For most mixer showers, the fix is a new thermostatic cartridge, cleaning the inlet filters, or resetting the temperature stop. That is usually a short job if the right cartridge is available. On an older or discontinued valve, particularly a concealed valve set into a tiled wall, the plumber may recommend replacing the valve instead. That takes longer and can mean some tile work, so it helps to know the make and model before the visit.
Our plumbing labour is £95 an hour, and the £60 call-out is waived on jobs over two hours. Parts depend on the valve, and the plumber confirms the price before starting. See our shower repair service for the full range of faults we fix.
Cold shower and no idea why?
Tell us the type of shower, whether the hot taps work and the make of the valve if you can see it. We'll arrange a plumber and confirm the price before any work starts.
📞 Call 020 7870 3200If the taps are cold too, see our no hot water repairs.
Frequently Asked Questions
Why is there no hot water in my shower but the taps are hot?
If the taps run hot, your boiler or cylinder is producing hot water, so the fault is in the shower. On a mixer shower that usually means the thermostatic cartridge is worn or scaled up, or the maximum temperature stop has moved. On an electric shower it is usually the heating element, a thermal cut-out or low flow through the unit.
Can limescale stop a shower getting hot?
Yes. Hard water leaves scale inside thermostatic cartridges and on the filters where water enters the valve. That can stop the cartridge moving to let enough hot water through, so the shower stays cool. Cleaning the inlet filters or replacing the cartridge usually fixes it.
Why does my shower go hot then cold?
The most common reasons are another tap or appliance drawing water at the same time, a combi boiler that cannot keep up at low flow and keeps switching off, a worn thermostatic cartridge that cannot balance the supplies, or a hot water cylinder that is running out.
Is it the boiler or the shower?
Run the hot tap in the basin or kitchen. If it gets hot, the boiler is working and the shower is at fault. If it stays cold too, the problem is the hot water supply, such as the boiler, a cylinder, a zone valve or an immersion heater. An electric shower is the exception: it heats its own water, so it can fail while everything else is fine.
How long does it take to fix a shower with no hot water?
Replacing a thermostatic cartridge or cleaning inlet filters is usually a short job, provided the right cartridge is available for your valve. Older or discontinued valves may need the whole valve replacing, which takes longer, especially if it is concealed in a tiled wall.