Guide hub
Hot Water, Cylinders & Tanks
Cylinders, storage tanks and the discharge pipes that give them away. Written from the leak end: what is losing water, where it is going, and what it costs to put right.
Hot water cylinder leaking: where it is coming from
The four places a hot water cylinder actually leaks, how to tell a real failure from condensation, and which faults are repairable rather than a new cylinder.
Unvented cylinder leaking from the top
Water at the top of an unvented cylinder is almost always a valve, a boss or a joint — not the cylinder. How to tell which, and what never to cap.
Which Pipe Is Dripping Outside? Discharge, Overflow or Condensate
Four different pipes drip outside a British house and they mean four different things. Work out which one you have from where it starts, not what it looks like.
Immersion heater leaking at the boss: what to check first
The element is 3kW of live electrics sitting in water. Isolate at the consumer unit first, then work out whether the washer, thread or cylinder has gone.
Vented or unvented cylinder, and how each one fails
A vented tank fails slowly into the ceiling under the loft. An unvented cylinder fails fast through the tundish. What each one does, and what it wrecks.
Megaflo cylinder leaks and what each one is telling you
Where a Megaflo actually loses water, why the discharge pipe drips, how the internal air gap is recharged, and when the cylinder itself is finished.
Smart and heat-pump cylinders: where they actually leak
Mixergy, stratified and heat-pump cylinders add sensors, valves and tappings. What is genuinely new, what leaks on any cylinder, and what a fault code is not.
How long a hot water cylinder lasts, and when to replace it
What really decides a hot water cylinder’s life: hardness, running temperature, material and the expansion vessel. The signs it is finished, not fixable.
No Hot Water: When It Is Actually a Leak
Most no hot water faults are a control, a diverter valve or a thermostat, not a leak. How to tell in two minutes whether yours is the exception.
Hot water cylinder thermostat: where it is and how it fails
The cylinder thermostat is strapped to the tank under the insulation, which is why you cannot find it. What it does, how it fails, and when it becomes a leak.
Hot water goes cold too quickly: how to find out why
Running out of hot water sooner than you used to has a short list of causes. How to time it, turn the minutes into litres, and work out which one you have.
Airlock or leak? Why air keeps coming back in a hot water system
Clearing an airlock on a gravity-fed system takes ten minutes. Air that is back within weeks is a different fault: the system is drawing it in.
No hot water? What to check in the first ten minutes
Five checks that cost nothing, before anyone charges you to attend: heating as well or not, the fuse box, the programmer, the pressure gauge, and damp.
Cold Water Storage Tank Leaking in the Loft
A loft tank holds a couple of hundred litres above your ceilings and fails when nobody is up there. Where they leak, how to isolate one, what not to stand on.
Loft tank overflowing: stop it now, then fix the float valve
An overflowing loft tank is nearly always the float valve. Tie the arm up to stop the flow in seconds, then fix the cause — and know when it is an emergency.
Which Tank Is That Overflow Pipe Coming From?
An overflow pipe dripping outside is fed by one specific tank, cistern or valve indoors. Where it leaves the wall tells you which one, and how to prove it.
Condensation on a Cold Water Tank, or a Leak? The Foil Test
A cold tank in a warm loft sweats, and the drips get reported as a leak every winter. Tape foil over the wet spot and you will know which one you have.
Removing a redundant cold water tank
A loft tank left full and connected after a combi or unvented conversion is a slow leak waiting to happen. When to decommission it, and when it has to stay.
Solar and heat pump cylinder leak points
Twin-coil and heat pump cylinders carry more joints, a bigger coil and often a glycol primary. Where they leak, how glycol behaves, and what nobody knows yet.
Leaks on a secondary hot water circulation loop
A secondary return keeps hot water moving around the building all day. A pinhole on that loop never stops running, and the heating bill hides the water bill.
Commercial hot water plant leaks, found on a live system
How leaks in calorifiers, buffer vessels, plate heat exchangers and communal risers get traced in London blocks without taking the hot water off the building.
What hard water does to a hot water cylinder in London
London water is hard, and scale is why cylinders and immersion elements age badly. What it does inside the tank, and what a softener will and will not fix.
What a cylinder replacement costs in London
What actually drives the price of a hot water cylinder replacement, what an honest quote should itemise, and why we will not quote for the installation itself.
Megaflo no hot water: identify the fault before booking a repair
Separate no flow from cold water, identify a direct or indirect Megaflo, and record the controls and symptoms needed for a useful cylinder repair visit.
Santon PremierPlus fault finding: no hot water, flow and discharge
Identify your Santon PremierPlus cylinder and distinguish cold water, no flow, short hot-water supply and safety discharge before arranging the right repair.
Range Tribune cylinder fault finding: no hot water, discharge and leaks
Identify your Range Tribune cylinder and separate heating, flow, discharge and external leak problems. Prepare the right evidence for an unvented-cylinder engineer.
No Hot Water in the Shower? What Has Failed and Why
Hot at the kitchen tap but cold in the shower? Usually the valve cartridge, a scaled inlet filter or a stuck check valve. How to tell which, and the fix.
If you need the repair
Other guide hubs
Boiler & Heating Pressure
A sealed system that will not hold pressure is losing water somewhere. What each fault code means, and how to find where it is going.
Thames Water
The letter, the four-week window, the allowance, and exactly where Thames Water’s pipe stops being their problem and starts being your repair bill.
Water Bills & Meters
Reading the meter to prove a leak, what an unexplained jump actually costs you per day, and the evidence a water company wants before it grants an allowance.
Insurance Claims & Trace and Access
Written from the engineer’s side: what the loss adjuster asks for, what a trace report must contain, and what gets a claim declined.
Field Notes
What we actually find on London leaks, what the law and the insurers changed this year, and the jobs worth writing up.