Replacing a radiator valve
Check the steps below first — if you're not confident, get it fixed safely today.
Post a job — we'll find you an engineer →⚠️ Do not attempt to remove a radiator valve without draining the system first — it will flood.
Radiator valves are hardworking components that regulate water flow and temperature, but they don't last forever. After years of constant use, the seals inside wear out, the valve body can crack, or the connection joint starts to weep — and suddenly there's a puddle underneath your radiator. This is one of the most common heating problems householders face, especially in older properties or homes with hard water. The good news is that a minor weep from the gland nut (the top connection) can sometimes be fixed with a simple tightening, but a cracked valve body or serious leak demands professional attention because the entire heating system must be drained first to prevent flooding your home. This guide walks through the warning signs and shows when a quick fix might work — and crucially, when to call in a qualified plumber instead.
Not sure if this matches your problem?
Use our interactive tool — answer a few questions and get a personalised diagnosis.
Most likely cause & what to check
Check if the valve is just dripping from the joint at the top (gland nut) — sometimes a gentle half-turn clockwise on the gland nut with a spanner can stop a minor weep.
If the valve body itself is cracked or leaking badly, do not attempt to remove it yourself. The system needs to be drained first.
Call a plumber. Tell them: "I have a leaking radiator valve — it's dripping from [describe where]."
Unlock the full step-by-step guide
This guide has more steps written by a qualified plumbing and heating engineer — subscribe to see them all and save yourself a costly call-out.
Frequently asked questions
How do I know if my radiator valve is actually leaking or just sweating?
A sweating valve will have condensation on the outside, but the radiator itself remains dry underneath. A genuinely leaking valve will leave water pooling on the floor, windowsill, or carpet beneath it, often with a steady drip. If you're unsure, place a piece of kitchen roll under the valve — if it gets wet within a few minutes, the valve is leaking and needs attention.
Can a leaking radiator valve damage my flooring or walls?
Yes — persistent dripping can cause real damage to wooden floors, carpets, and plasterwork, leading to rot, mould, and structural issues if left unaddressed. Even a slow leak adds up quickly, so it's worth getting it sorted within a few days rather than waiting. The sooner a plumber drains and replaces the valve, the safer your home remains.
Will my whole heating system need to be drained to replace a single radiator valve?
In most cases, yes — the entire system needs to be depressurised and drained before a valve can be safely removed, otherwise water will pour out everywhere. Some modern systems have isolation valves that allow a single radiator to be shut off, but this still requires expertise to do safely. A Gas Safe registered engineer will assess your system and drain only what's necessary, then refill and bleed the system afterwards.
Is it cheaper to tighten the gland nut myself or call a plumber straight away?
A gentle half-turn on the gland nut costs nothing and takes 30 seconds — if it stops the drip, brilliant. However, if that doesn't work or the leak is from the valve body itself, a plumber call-out is unavoidable because the system must be drained professionally. Don't waste time attempting to disassemble the valve yourself, as this will flood your property and create a much costlier emergency.