Worcester Bosch Greenstar: Pressure dropping frequently

1. 1. Check for visible leaks on the boiler and heating system.

   Why: Visible leaks are the most straightforward cause of pressure loss and can often be easily rectified.

   How: Inspect all accessible pipework, radiator valves, and boiler connections for any signs of water, damp patches, or corrosion. Pay close attention to radiator valves and joints.

2. 2. Inspect the Pressure Relief Valve (PRV) discharge pipe.

   Why: A faulty PRV can release water from the system, leading to pressure drops, even without visible internal leaks.

   How: Locate the copper discharge pipe, usually exiting the boiler and terminating outside. Check for any signs of dripping or water staining at the end of the pipe.

3. 3. Check the system pressure and repressurise if necessary.

   Why: Low pressure will cause the boiler to stop working as a safety measure, and repressurising is a temporary measure to restore operation.

   How: Observe the boiler's pressure gauge; it should typically be between 1 and 1.5 bar when the system is cold. If below 1 bar, use the internal or external filling loop to bring the pressure back up to the recommended level, following the manufacturer's instructions for your specific filling method.

4. 4. Test the expansion vessel.

   Why: A faulty or uncharged expansion vessel cannot absorb pressure fluctuations, leading to the PRV discharging water and subsequent pressure loss.

   How: Isolate the boiler, drain the system pressure, and check the expansion vessel's charge pressure with a suitable gauge. Re-charge or replace as necessary, referring to manufacturer guidelines.

5. 5. Check for hidden leaks in the heating system.

   Why: Slow, consistent pressure drops often indicate small, hidden leaks that are not immediately visible.

   How: Consider using leak detection fluid in the system or carefully inspecting areas with underfloor pipework for subtle signs of dampness or water damage. This may require lifting floorboards.

6. 6. Examine the automatic air vent (AAV).

   Why: A faulty AAV can allow water to escape or air to enter the system, contributing to pressure fluctuations.

   How: Inspect the AAV for any signs of weeping or blockage. If faulty, it may need cleaning or replacement.

Commonly failed parts

• Pressure Relief Valve (PRV)
• Expansion Vessel
• Automatic Air Vent (AAV)
• Filling Loop (if external and faulty)
• Radiator valve repair kits/replacement valves

Sources

The AI cross-checked the following manufacturer and trade sources while producing this checklist.

• worcester-bosch.co.uk
• justanswer.co.uk
• artonheat.co.uk
• worcester-bosch.co.uk
• go-assist.co.uk
• iheat.co.uk
• worcester-bosch.co.uk