THE SHORT ANSWER
What is affected?
First compare a few taps you already use normally. Is one hot outlet cold, are several hot taps affected while cold water still works, or are both hot and cold outlets dry? The pattern helps you choose the next contact but does not identify a failed part. Combi boilers heat water on demand; a cylinder stores water heated beforehand. An electric shower heats its own cold supply, so a cold shower alone is not proof of a central hot-water problem.
Jump to a section
Is there a separate urgent warning sign?
| What is happening | Why it matters | Next step |
|---|---|---|
| There is no hot water, but no other warning sign | This symptom alone does not indicate a gas leak or carbon monoxide. | Use the outlet comparisons below; do not open or reset a boiler. |
| You smell gas, a gas appliance seems unsafe, or a CO alarm/suspected exposure is present | These are separate gas-safety concerns; no-hot-water is not the indicator. | Stop troubleshooting and follow the conditional guidance below. For a suspected gas leak or CO from a gas appliance, contact your local gas emergency service immediately. |
| A hot outlet becomes unexpectedly very hot or cannot be controlled normally | Excessively hot water can scald. | Stop using it and seek prompt competent plumbing/heating advice; do not test again or adjust stored-water controls. |
If gas or carbon monoxide is separately suspected
If a gas leak or carbon-monoxide exposure is separately suspected, stop troubleshooting. For possible CO exposure, stop using the suspected appliance if possible, open doors/windows, go outside and get medical advice. Contact the relevant local gas emergency service for a suspected gas leak or CO from a gas appliance; do not use an appliance suspected unsafe until checked by a Gas Safe registered engineer. Call 999 for severe breathing difficulty, sudden confusion or loss of consciousness. No-hot-water alone is not evidence of gas or CO.
Is one outlet affected, or several?
Use taps you already use normally; do not run water for an extended test. Note whether hot water is absent or just cooler than usual, whether cold water still flows, and how many outlets are affected. This pattern helps route the next step but does not identify a fault.
| What you notice | What it may suggest | Useful next step |
|---|---|---|
| One hot tap is cold, while other hot taps work | Only one outlet differs in your checks so far; this does not identify the fault. | Use the matching tap guide or report the outlet to your landlord/plumber. |
| Several hot taps are cold, but cold water works | A wider hot-water availability issue is possible; system type and controls vary. | Identify the system only from a visible label or exact manual. Use the bounded control check below if it applies. |
| Several hot and cold taps have no water | A wider incoming supply interruption is possible. | Check current information from your own water supplier and report which outlets are dry. |
| Only an electric shower is cold | An electric shower heats its own cold supply; this alone does not show that the home’s central hot water is affected. | Use the exact shower manual and the electric-shower guide. |
| A known cylinder system ran short after unusually high use | Stored hot-water volume may have been depleted; recovery time depends on the system. | Allow only its familiar normal heating period. Persistent loss needs advice. |
| You are unsure what type of system you have or what is affected | Appearance may not reveal hidden connections or controls. | Use visible labels/manuals and taps already used normally; record what you know and ask the operator/installer. |
One local outlet has a different symptom
If water flows from one mixer tap but remains only hot or only cold, use its matching guide. If the water supply is missing, compare other taps as a separate check. A cold shower has its own mixer/electric distinction.
Helpful tools: Find the right plumbing guide. Use these with the guidance above.
How does your home heat its hot water?
HEATS ON DEMAND
Combi boiler
A combi heats water as it is drawn at a tap. Some models have a preheat feature that affects response time; the exact manual explains what the displayed mode means. Do not assume a central-heating timer controls hot-water production.
STORES WATER
Hot-water cylinder
A cylinder stores water heated beforehand. It may be heated by a boiler, heat pump or another system; the cylinder itself does not tell you which. Some identified systems have a separate hot-water timer channel.
INDEPENDENT SUPPLY
Electric shower
An electric shower heats incoming cold water in the shower unit. One cold electric shower does not prove that hot taps or a central hot-water system are affected.
What can you check without changing the system?
Compare normal outlets
At a few taps you already use normally, note whether hot and cold flow, and whether the problem is at one outlet or several. Close each tap normally after checking; do not leave one open while waiting for supply to return.
Identify the system only if you can
Use a visible model label or the exact user guide already available. A combi heats on demand; a cylinder stores heated water, and the heat source varies. If you are unsure, leave the controls alone and ask the landlord, installer or building operator.
Check one familiar hot-water timer only when the exact manual fits
For a positively identified cylinder system, if its exact user guide confirms a separate hot-water timer/programmer channel and you recognise the control, check whether the hot-water period is scheduled/on. If it is off and that manual clearly describes an ordinary user ‘on’ or ‘boost’ option, use it once as directed. Do not change any other setting. This step does not apply to a combi unless its own manual specifically describes that function.
Keep the check to normal user controls
Do not reset or repressurise the boiler, remove a cover, turn an unfamiliar valve, adjust a cylinder thermostat or immersion heater, change stored-water temperature, or inspect wiring. Do not infer a failed valve or boiler part from the symptom.
Write down what you know
Record when it began, affected outlets, whether cold water works, any model/control display visible without moving anything, and recent work or unusually high use already known. A pattern helps someone assess the issue; it does not diagnose it.
Do not keep repeating a check
If one permitted normal hot-water timer check does not restore the expected service in the next familiar scheduled period, stop adjusting controls and ask for help. Repeated boosts do not establish a cause.
Sources
- Triton Showers - What are the different home water systems?
- Drinking Water Inspectorate - Water Storage Tanks and Cisterns
- Water UK - What to do if you lose your water supply
- Thames Water - No water or low pressure
- Vaillant UK - What is a system boiler?
- Vaillant UK - ecoTEC pro
- Ideal Heating - Logic Plus Heat User Guide
- Worcester Bosch UK - Why might I want to programme hot water times with my combi boiler?
Who should you contact?
LANDLORD OR BUILDING OPERATOR
Several hot outlets are affected
Report which hot outlets are cold, whether cold water still works, when it began and any visible control message or known work. Shared systems and responsibilities vary; the symptom does not identify the failed part.
WATER SUPPLIER
Several hot and cold outlets have no water
Check live interruption information from your own supplier and ask for service status. Supplier help is relevant to a wider cold-water supply interruption, not a single cold hot tap.
PLUMBER OR INSTALLER
One hot outlet stays cold, or the wider issue persists
Give the outlet pattern, system/model if known, onset, visible message and known recent work. Ask them to identify the system and cause before proposing parts or work.
The cost depends on the system, the diagnosed fault and the work required. Before agreeing to a visit or repair, ask what the diagnostic/attendance charge includes, whether labour and parts are separate, VAT, any return-visit or out-of-hours fee, what evidence supports the proposed repair and whether the quote changes if a different cause is found.
Helpful tools: Plumber visit checklist. Use these with the guidance above.
Questions about no hot water
Does a cold shower mean the whole house has no hot water?
Not necessarily. A mixer shower uses hot and cold supplies, while an electric shower heats its own cold feed. Compare other taps you already use normally; a cold electric shower alone does not establish a central hot-water problem.
If my cold taps work, does that prove the boiler is at fault?
No. Several hot outlets cold while cold water works suggests a wider hot-water availability issue, but it cannot identify the boiler, cylinder, timer or any component. Use only a familiar exact-manual control check and report the pattern.
Could the water have run out?
A cylinder stores a finite amount of hot water and unusually high use can deplete it. Recovery depends on the system; if the problem persists beyond its familiar normal heating period, ask the operator or installer.
Should I reset or top up the boiler?
This guide does not recommend resetting or topping up the boiler. No hot water alone does not establish that pressure or a particular boiler function is the cause. Ask your landlord, building operator or an appropriately qualified professional.
EVIDENCE & ACCOUNTABILITY
Sources and review
Prepared by Plumber.org.uk with AI assistance, using the sources listed below. These sources support the explanations; they do not endorse this website.
Source and editorial checks completed. Professional plumbing review has not been carried out. Initial research: 2026-09-29. Updated: 2026-09-30. This is general information, not an assessment of your installation. Prices can change; confirm compatibility and the full repair quote before buying or booking.
How we research and update guides. Spotted an error? Contact us with the page address and the detail to check. This form is for general enquiries and editorial feedback, not emergency assistance.
- Triton Showers - What are the different home water systems?
Accessed 2026-09-29; sections on mixer and electric showers describe mixer hot/cold supplies and electric showers heating a cold mains feed in the unit.
- Health and Safety Executive - Scalding risk from domestic hot water systems - safety alert
Previously checked 2026-09-28 in accepted mixer-tap research; warning sign is excessively hot water on certain stored-water/immersion-heater systems; recommends competent advice and no homeowner adjustment. Original access date retained.
- Drinking Water Inspectorate - Water Storage Tanks and Cisterns
Accessed 2026-09-28. “Do I have a water storage tank?” lines 34 - 38: some older properties have tank-fed cold taps; in newer homes, especially with unvented heating systems, hot and cold taps are likely supplied directly under mains pressure. Used only to establish household supply variation where multiple outlets share a symptom.
- Water UK - What to do if you lose your water supply
“What to do if you lose your water supply”: cold kitchen tap, inside stop valve, neighbour and water-company live issue checks.
- Thames Water - No water or low pressure
Sections “Try your cold kitchen tap”, “Check your stop valves”, “Ask your neighbours”, “Check issues in your area”.
- Vaillant UK - What is a system boiler?
Accessed 2026-09-29; section ‘Is a system boiler the same as a combi boiler?’ says system boilers have a cylinder storing hot water for later use whereas combi boilers heat on demand; lines 186 - 203 explain stored quantity can be depleted during unusually high use and a system then reheats it.
- Vaillant UK - ecoTEC pro
Accessed 2026-09-29; product page describes this identified combi boiler as providing hot water on demand without a separate hot-water cylinder.
- Ideal Heating - Logic Plus Heat User Guide
Accessed 2026-09-29; section 1.6 troubleshooting, ‘NO HOT WATER’: tells users of this specified heat-only/cylinder boiler to ensure the hot-water timer is on and that the cylinder thermostat is calling for heat, then contact service/Gas Safe engineer if the fault persists. This guide adopts only the exact-model hot-water timer channel check, not thermostat adjustment or service steps.
- Worcester Bosch UK - Why might I want to programme hot water times with my combi boiler?
Accessed 2026-09-29; sections ‘The ECO button explained’ and ‘Programming the times for your hot water’ explain that on this wall-hung gas combi range the timed function controls preheat/response time, while hot water is still heated when a tap is opened; simple mechanical controls may operate central heating only.
- Health and Safety Executive - Gas safety - Home owners
Accessed 2026-09-29; section ‘What should I do if I suspect an appliance is unsafe?’ says not to use it until checked by a Gas Safe registered engineer; gas leak steps include calling 0800 111 999. Used only for a concise conditional warning, not ordinary no-hot-water triage.
- Health and Safety Executive - Gas safety - Carbon monoxide awareness frequently asked questions
Accessed 2026-09-29; ‘What should I do if I think my appliance is spilling carbon monoxide?’ says call the National Gas Emergency Service on 0800 111 999, switch off the appliance/shut gas at meter, ventilate; symptoms listed on the page include headache, dizziness, nausea, breathlessness and loss of consciousness.
- NHS 111 Wales - Carbon monoxide poisoning
Accessed 2026-09-29; ‘What to do if you think you have carbon monoxide poisoning’ says stop using suspected appliance if possible, open doors/windows, go outside and get medical advice; urgent medical emergency signs include severe breathing difficulty, sudden confusion or loss of consciousness. The page states it is adapted from NHS content.