Heatline D020103888 3-Way Valve Body

The Heatline D020103888 is a three-way valve body — the housing section of the diverter assembly that directs water between the central heating circuit and the domestic hot water circuit in a combination appliance. It is supplied by Heatline as a spare for their standard water heater range. The body carries the ports and internal seats that the moving valve parts work against, so it is the component replaced when the housing itself is worn, scaled or damaged rather than when the actuator or motor has failed.

• Domestic hot water runs but the radiators stay cold, or the reverse, with no response at the tap or thermostat
• Water passing through the valve body when the circuit should be shut, or noticeably restricted flow on one side
• Scale, corrosion or hairline cracking visible around the body or its ports
• Weeping from the body itself or from the joint faces where it meets the manifold
• Repeated actuator or motor failures traced back to a stiff, scored or damaged valve body

• Match D020103888 against the number stamped on the existing valve body or listed in the appliance parts breakdown.
• Check the appliance model and serial number to confirm the correct variant for your unit.
• Inspect the O-rings and seals that sit against the valve body and renew them if they are flattened, swollen or perished.
• This is not a gas-carrying component, but the appliance should still be isolated and the water circuit drained before the body is removed.