Baxi Hydroblock Flow 720398901

The Baxi Hydroblock Flow is a hydraulic assembly that sits in the domestic hot water circuit of the appliance, where it handles the flow of water through the DHW side of the boiler and provides the reference point for the flow sensing that tells the control board hot water has been drawn. It is supplied by Baxi under part number 720398901 and is listed against the Broag commercial appliance range.

Because the hydroblock carries mains-pressure water and houses moving sensing components, it is a serviceable item that is replaced rather than repaired when the flow side stops responding or begins to weep.

• No hot water or the boiler fails to fire when a hot tap is opened
• Domestic hot water runs intermittently, cutting in and out during a draw-off
• The appliance reports a DHW flow fault or fails to register a demand
• Water weeping or dripping from the hydroblock body or its connections
• Scale or debris build-up inside the flow side causing erratic sensing

• Confirm the appliance model and, where available, the serial number against the compatibility list before ordering
• Check the part number on the existing component against 720398901, as the alternative number 1132487 may be marked on older stock
• Inspect the O-rings and seals on the hydroblock connections and renew them if they are flattened or perished
• This is not a gas-carrying component, but work inside the appliance casing should still be carried out by a competent person