A drop in your boiler’s pressure gauge can send shivers down any homeowner’s spine. Cold showers and disrupted heating are undesirable consequences, but before you reach for a heating engineer in Plymouth, let’s understand the potential causes and see if a simple fix might be in order.

The Usual Suspects

The most usual and underlying causes behind your boiler losing pressure could be the following:


This is the most common culprit. Check for visible drips around the boiler, pipes, and radiators. Tiny leaks might not be readily apparent, so paying attention to damp patches, flaking paint, or water stains near your system can offer clues.

Air in the System

Bleeding your radiators regularly removes trapped air, but sometimes air pockets can sneak in after maintenance. Listen for hissing sounds from radiators, which might indicate airlocks.

Faulty Pressure Relief Valve (PRV)

This safety feature releases excess pressure to prevent boiler damage. While uncommon, a malfunctioning PRV can trigger pressure loss. As a potential indicator, listen for continuous water discharge from the PRV safety pipe.

Faulty Expansion Vessel

This component absorbs pressure fluctuations in the system. A faulty vessel can’t accommodate pressure changes, leading to a drop in the gauge.

Recent Bleeding

Have you bled your radiators lately? While necessary, releasing air might also remove some water, causing a temporary pressure dip. Top up the system using the filling loop per your boiler’s manual.

What You Can Do

If you come across an abrupt pressure drop in your boiler, here are a few things you can do:

Check the Pressure Gauge

Consult your boiler manual for the ideal pressure range. Topping up might be necessary if the pressure is above the safe minimum. Use the filling loop cautiously and follow the instructions to avoid overfilling.

Bleed Your Radiators

If airlocks are suspected, bleed your radiators according to the manufacturer’s instructions. Start with the highest radiator and work your way down, releasing air until water flows steadily. Remember, this might cause a temporary pressure drop, so top up afterwards if needed.

Visual Leak Inspection

Take a flashlight and scrutinise pipes, connectors, and the boiler for any signs of water escape. Even minor leaks can cause pressure loss over time.

When to Call a Professional

If the pressure remains low after these checks, a professional is recommended. They have the expertise to diagnose complex issues like faulty valves, damaged components, or internal leaks. Additionally, if you need clarification on any DIY steps, seek professional help.

Is your boiler losing pressure due to some inexplicable reason? As a leading heating engineer service, PJ Plumbing and Heating can help you out. Reach out to us today.