Motorised Zone Valve Repairs & Replacements
Two-Port & Three-Port Valves for Central Heating & Hot Water Systems
If your boiler is working but your heating or hot water isn't responding correctly, the problem is often a faulty motorised valve, a small but critical component that controls where hot water flows in your system. I repair and replace two-port and three-port motorised zone valves, diagnosing the fault accurately before recommending the right solution.
How Motorised Valves Work
A motorised valve is an electrically operated valve that controls the flow of hot water within your central heating system. Working alongside your programmer, room thermostat, and cylinder thermostat, it opens and closes automatically to send hot water where it's needed — either to your radiators, your hot water cylinder, or both. When everything is working correctly, you won't even know it's there. When it fails, your heating or hot water stops responding as it should.
Common Symptoms of a Faulty Motorised Valve
Motorised valve faults can present in several ways, and because the symptoms often overlap with other heating system problems, accurate diagnosis is essential before carrying out any work. Common signs include:
- Heating not coming on despite the boiler firing
- Hot water working but radiators staying cold, or vice versa
- Heating or hot water running continuously without responding to the thermostat
- A clicking or humming noise from the valve without it fully opening or closing
- The system only responding when the manual override lever on the valve is engaged
Two-Port Motorised Valves
A two-port motorised valve acts as an electrically controlled on/off switch within your central heating system, opening to allow hot water to flow through a circuit and closing to stop it. They are most commonly found in S-Plan heating systems, where separate valves control the flow to the heating circuit and the hot water cylinder independently. When a two-port valve fails, either the valve sticks open, causing the heating or hot water to run continuously, or it sticks closed, completely cutting off flow to that part of the system.
Three-Port Motorised Valves
A three-port motorised valve has a single inlet and two outlets, and is used to direct hot water between two circuits, typically between the central heating radiators and the hot water cylinder. There are two types commonly found in UK homes: the diverter valve, used in W-Plan systems, which directs water to one circuit at a time, and the mid-position valve, used in Y-Plan systems, which can supply heating, hot water, or both simultaneously depending on demand. When they fail, the symptoms can be harder to diagnose, a system that only heats water but not radiators, or vice versa, is a classic sign.
Head Replacement vs. Full Valve Replacement
Not every motorised valve fault requires a full valve replacement. In many cases, only the actuator head, the motorised part that sits on top of the valve body, has failed, while the valve body itself remains perfectly functional. Replacing just the actuator head is quicker, less disruptive, and does not require draining down the system, making it a more cost-effective solution when the valve body is in good condition. I always assess whether a head replacement is sufficient before recommending a full valve replacement, keeping the work and cost to the minimum necessary to resolve the problem.
Brands I Work With
Motorised valves from different manufacturers vary in design, wiring configuration, and actuator type, which means knowing the specific brand and model makes a real difference when diagnosing a fault or sourcing the right replacement part. I work with motorised valves from all major manufacturers commonly found in UK homes, including Honeywell Home, Drayton, Danfoss, Salus, Sunvic, and Siemens, among others.
In many cases, replacement actuator heads are available separately and are brand-specific ,a Honeywell head, for example, will not fit a Drayton valve body. Where a head replacement is sufficient, I source the correct part for the specific make and model of your existing valve, avoiding the need for a full valve replacement wherever possible. Where a full replacement is necessary, I fit a like-for-like unit or a compatible alternative, ensuring the new valve integrates correctly with your existing system wiring and controls.
Heating or Hot Water Not Working?
A faulty motorised valve is a common cause. Get in touch and I'll find the problem and put it right.