Plumbing · Croydon, London
Hot Water Cylinder Repair in Croydon
Lukewarm water, a drip from the airing-cupboard floor or a hiss from a discharge pipe all point at the cylinder, and the right response depends on which kind you own. [Proper Plumber Croydon](/) takes your call on 07898 116196 at any hour and passes cylinder faults to independently owned local partner companies, who identify whether it is vented or unvented before they open a toolbox.
That distinction is the difference between a simple repair and one that must follow rules. A vented cylinder is fed by a loft tank and runs at low pressure; an unvented cylinder runs at mains pressure with expansion vessel, temperature and pressure relief valve and a discharge pipe, and Building Regulations Part G3 governs how it is fitted and serviced.
Published London pricing gives a sense of scale. A new cylinder costs roughly £1,215 to £2,970 installed, with a like-for-like vented tank swap at about £500 to £1,200 and an unvented cylinder installed at £1,800 to £4,000 or more. These are published ranges, not our quotes, and the partner company confirms the price in writing once they have seen the installation.
Local water matters here. Thames Water's Croydon East supply measured 308 mg/l as calcium carbonate in 2025, which is very hard, so an immersion heater element can be coated in scale within a few seasons and cylinders lose capacity as limescale settles at the base. Many 1930s semis in Shirley still have an airing-cupboard cylinder, and many have never had the element or thermostat changed.
If the cylinder is leaking from the body, repair rarely helps; if only a thermostat, element or valve has failed, repair is usually the better spend. The first visit establishes which.
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What We Do
Cylinder Faults We Trace and Repair
Cylinders fail in a handful of predictable ways, and each has a different remedy.
No Hot Water or Only Lukewarm
A failed immersion element, a tripped thermostat, a motorised valve that has stuck or a coil choked with scale can each leave the cylinder cold. The partner company tests the heat source and controls in turn, so only the failed component is replaced.
Leaks, Weeping Joints and Dripping Discharge Pipes
Weeping flanges and fittings are repairable, but water streaming from the body of the cylinder means the vessel has failed and needs replacing. A pipe dripping outside an unvented cylinder can mean a faulty pressure relief or expansion vessel, which should not be ignored.
Unvented Cylinder Safety Devices
An unvented cylinder carries a temperature and pressure relief valve, an expansion vessel and a tundish with discharge pipework. These are safety devices, so any fault is dealt with promptly and the work is done to Part G3 and the manufacturer's instructions.
The Benefits
How a Cylinder Is Properly Assessed
Repair, upgrade or replace is a decision that should rest on what the cylinder is actually doing.
Identify the Type First
The partner company checks the labelling, the pipework and whether there is a loft tank. That tells them which regulations apply, which parts are compatible and whether any previous work looks wrong.
Test Before Replacing
Thermostat, element and valve are tested individually. Replacing a £50 part is a very different bill from replacing a cylinder, and the written quote reflects what failed rather than what is dearest.
Replacement Done to Part G3
A new unvented cylinder needs the right discharge route, tundish and safety devices, and the work must be notified to building control. The partner company provides the commissioning paperwork you will need for a warranty claim or a house sale.
Good to Know
Signs of Cylinder Trouble
Spot these early and the repair stays small.
When to Call About Your Cylinder
Any of these needs a look.
- Hot water runs out much faster than it used to
- Rumbling or banging from the airing cupboard
- Dampness or green staining beneath the cylinder
- Water dripping from a discharge pipe outdoors
- Immersion switch tripping the fuse
What to Do Right Away
These keep the damage down.
- Switch off the immersion heater at the fused spur
- Close the cold feed to the cylinder if it is leaking
- Do not touch a hissing or steaming discharge pipe
- Mop and protect the floor beneath
- Note the cylinder make and any label details
Why Us
Cylinders From Addiscombe to Upper Shirley
The housing stock dictates the cylinder, and the cylinder dictates the repair.
Interwar Semis and Their Airing Cupboards
The 1930s semis of Shirley and Monks Orchard commonly have a copper cylinder in the airing cupboard fed from a loft tank. Those are repairable and often outlast the boiler, but lagging, thermostats and elements deserve attention.
Larger Homes Moving to Mains Pressure
Some of the bigger detached houses in Upper Shirley have been fitted with unvented cylinders to give strong showers on every floor. Those need an annual check of the safety devices, which is a separate service from a repair.
A Named Partner by Text
We text you the partner company's name before they arrive. They quote, repair or replace, invoice and take payment directly, and if the problem returns you ring us and we chase it.
A cylinder rarely fails alone: a heating-coil fault often traces back to the boiler, so the pages on emergency boiler repair and boiler installation are worth reading together. Cold radiators beside a cold cylinder suggest a shared fault covered under central heating repair, and a cylinder leak that has already reached a ceiling is a case for leak detection and repair. A new cylinder can pair with a bathroom installation. We work in Shirley, Addiscombe and South Norwood. See all services.
What Cylinder Repair Covers
A hot water cylinder stores heated water for taps, baths and showers. Repair covers the immersion heater, thermostats, heating coil connections, motorised valves, joints and, on unvented models, the safety devices and discharge pipework. Replacement is the answer when the vessel itself has corroded or split.
Unvented work follows Part G3 of the Building Regulations, and installation follows the manufacturer's instructions. Pipework and fittings must meet the Water Supply (Water Fittings) Regulations 1999.
What Affects the Price of a Cylinder Job
Repair or Replace
A thermostat, element or valve is a small bill; a replacement cylinder is a large one. The quote separates the two so you can see why replacement is recommended, if it is.
Vented or Unvented
Swapping a vented tank for another costs least. Moving to unvented adds safety devices, a discharge route and notification, which is why it sits higher in the published ranges.
Protecting a Cylinder in Hard Water
Scale on the Element
An immersion element in 308 mg/l water can be encased in limescale within a few seasons, so it heats slowly and fails early. Replacing it is usually the cheapest cylinder repair there is, and a new one lasts longer if the thermostat is set no higher than needed.
Lagging and Standing Losses
A well-lagged cylinder holds heat for much longer, which lowers the cost of every bath. An old foam jacket that has slipped or crumbled is worth replacing during any visit to the airing cupboard.
When the Cylinder Has Reached the End
A cylinder that has corroded through cannot be patched safely. The partner company explains the options, from a like-for-like swap to a move to mains pressure, and quotes each in writing so the decision is yours.
Deciding What to Spend
A Cylinder With Years Left
Where the vessel is sound and only a part has failed, a repair restores hot water for a fraction of a replacement. Ask the partner company to show you the failed part and explain why the rest of the cylinder is worth keeping.
Running Costs Matter Too
A badly insulated or scaled cylinder wastes energy every day. If you are replacing one anyway, ask about factory-insulated models and a thermostat setting that holds stored water hot enough without overheating it.
Paperwork for a Sale
If the home is on the market, unvented cylinder paperwork and a recent service record reassure buyers and their surveyors. Keep every commissioning certificate the partner company hands you.
Frequently Asked Questions
How much does hot water cylinder repair or replacement cost in Croydon?
Published London pricing puts a replacement cylinder at roughly £1,215 to £2,970 installed. Like-for-like vented tank swaps are around £500 to £1,200 and unvented cylinders at £1,800 to £4,000 or more. Smaller repairs, such as an element or thermostat, cost far less, and the partner company gives a written quote after seeing the installation.
How do I know if my cylinder is vented or unvented?
A vented cylinder is fed from a cold-water tank in the loft and usually has an open vent pipe above it. An unvented cylinder is connected straight to the mains and carries a label, an expansion vessel and a discharge pipe. If you cannot tell, the partner company identifies it on the visit, because the regulations differ.
My hot water has gone lukewarm. Is the cylinder broken?
Not necessarily. A failed immersion element, a faulty thermostat, a stuck motorised valve or scale on the heating coil can each cause it. Croydon East water measured 308 mg/l as calcium carbonate in 2025, which is very hard, so scale is a frequent culprit. The partner company tests each in turn before suggesting a new cylinder.
What should I do if my cylinder is leaking?
Close the cold feed valve to the cylinder, switch off the immersion heater at the fused spur and turn off the heating source if you can do so safely. Mop the area and protect the floor. A weeping joint is repairable, but water running from the body of the cylinder means it has failed and needs replacing.
Why is water dripping from the pipe outside my unvented cylinder?
The discharge pipe carries away excess pressure or heat from the safety devices, so a constant drip suggests a faulty relief valve, an expansion vessel that has lost its charge or incoming pressure that is too high. This is a safety matter and should be checked soon. Do not block the pipe, and do not touch it if it is steaming.
What rules apply to unvented cylinders?
Building Regulations Part G3 covers unvented hot water systems, including the safety devices, discharge pipework and notification to building control. Installation follows the manufacturer's instructions, and the work should come with commissioning paperwork. The partner company explains what applies when they see your cylinder, and you should keep the records. Ask the partner company for the commissioning record and keep it with the property papers.
Can I swap my loft-tank system for an unvented cylinder?
Often yes, if your mains supply is strong enough and there is space. It gives mains-pressure showers on every floor and frees the loft, but costs more than a like-for-like swap and brings the rules of Part G3. The partner company measures flow and pressure on the visit before recommending it. If mains pressure is weak, an unvented cylinder may disappoint, so the measurement matters before you commit.
How long does a cylinder replacement take?
A like-for-like swap normally takes a day, while a change from vented to unvented can take longer because of the new pipework, the discharge route and the safety devices. The quote should give the expected duration and tell you when hot water will be off, so you can plan showers around it. Draining, disconnecting and refilling all take time, and an unvented swap also needs the safety devices tested before hot water returns.
Do I need to service an unvented cylinder?
Manufacturers generally expect an annual check of the safety devices, such as the temperature and pressure relief valve, the expansion vessel and the tundish. It is a good habit and often a warranty condition. Ask the partner company what the maker requires for your cylinder and keep the record. A service takes under an hour and can catch a failing valve before it becomes an emergency or a flood.
Is an immersion heater a good backup if my boiler fails?
Yes. An immersion element can provide hot water while the boiler is being repaired, though it costs more to run on electricity. Switch it on only after confirming the cylinder is full of water and has no leak. If the element trips the fuse, switch it off and have it looked at. Remember to turn it off again when the boiler is back, or the electricity bill will show it.
Can you repair a cylinder at night?
The line is open 24 hours, so you can report a leak or a hissing discharge pipe at any time. Out-of-hours attendance depends on the severity and the partner company's availability, and the price is confirmed in writing before work starts. We never promise an arrival time. If water is escaping, close the cold feed and switch off the immersion before you ring, as that limits the damage.
