Water Tank Repairs
Hot water cylinders come in two genuinely different types — vented (fed from a cold water tank, usually in the loft) and unvented (mains-pressure, no loft tank needed) — and they fail in different ways, so the right repair depends on knowing which one you have before diagnosing the fault. Unvented cylinders in particular are subject to their own legal safety requirements (commonly referred to as G3), which means servicing and repair work on them needs to be done by someone specifically qualified for that system type.
What's Included
- Repairs for both vented (loft tank) and unvented (mains-pressure) cylinder systems
- Leak and pressure-fault diagnosis
- Heating-element and thermostat replacement
- Unvented cylinder servicing carried out to the correct (G3) standard
How It Works
- 1 Confirm which type of cylinder is fitted (vented or unvented) and what symptom is being seen
- 2 Isolate and inspect the cylinder, its valves, and immediate pipework
- 3 Diagnose whether the fault is the cylinder itself, a valve, the element, or a pressure/expansion issue
- 4 Repair or replace the faulty component and confirm safe, correct operation before leaving
Common Issues
- • Dripping or leaking pressure/temperature relief valves
- • Reduced hot water capacity from limescale build-up
- • Failed heating elements in electric or dual-fuel cylinders
Pricing: Typically £90–£250 depending on cylinder type and fault (indicative — confirm actual pricing with Rainbow Fix Ltd)
Water Tank Repairs — Frequently Asked Questions
How do I know if I have a vented or unvented cylinder?
If there's a cold water storage tank in your loft feeding the system, you almost certainly have a vented cylinder; if your hot water comes straight from the mains at full pressure with no loft tank involved, it's unvented. This matters because unvented systems have extra safety components (like an expansion vessel and pressure/temperature relief valves) that a vented system doesn't, and servicing them correctly requires specific (G3) qualification — it's worth mentioning which type you have, or letting the engineer confirm it, before any work is quoted.
Water is dripping from a valve on my cylinder — is that dangerous?
A small, steady drip from a pressure or temperature relief valve on an unvented cylinder can be normal under some conditions, but a constant or increasing flow is a sign the valve is either faulty or responding to a real pressure/temperature problem in the system, and shouldn't be ignored. If you're unsure which situation you're in, it's worth getting it checked rather than assuming it's fine, since these valves exist specifically to prevent a genuinely dangerous pressure build-up.
My hot water runs out much faster than it used to — what causes that?
This is commonly caused by a failing heating element (in an electric or dual-fuel cylinder), a build-up of limescale reducing the cylinder's effective heating surface — a particularly common issue given how hard the water is across this whole region — or a fault in the cylinder thermostat causing it to under-heat the stored water. Limescale build-up specifically tends to get worse over time rather than appearing suddenly, so if this has been gradually getting worse over months, that's a useful detail to mention.
Does an unvented cylinder need servicing even if nothing seems wrong?
Yes — unvented cylinders should be serviced annually regardless of whether there's an obvious fault, because the safety components (expansion vessel, relief valves) can degrade without any visible symptom until they fail, and manufacturer warranties typically require proof of annual servicing to remain valid. This is a genuinely different maintenance requirement to a vented system, which doesn't carry the same legal servicing expectation.