Common Boiler Problems, Issues & How to Resolve Them

A Homeowner & Landlord Guide

GAS TECH PLUMBERS LTD – Gas Safe Registered Engineers

A boiler is the beating heart of your home’s heating system. When it’s working properly, you barely notice it. When it isn’t, the problems are immediate — no heating, no hot water, strange noises, leaks, or error codes.

This guide explains the most common boiler problems, what typically causes them, what you can safely check yourself, and when you must call a qualified Gas Safe engineer. It’s written for homeowners and landlords across Lancashire & Greater Manchester and reflects real-world repair experience

Important Boiler Safety Warning

⚠️ Any work involving gas, combustion, flues, ignition systems, or removing the boiler casing must only be carried out by a Gas Safe registered engineer. Never attempt to dismantle or tamper with internal boiler components yourself pasted.

1. No Heating or No Hot Water

Typical Symptoms

• Boiler is on but radiators remain cold

• Hot water works but heating doesn’t (or vice versa)

• Boiler runs but temperature never increases

Common Causes

• Thermostat or programmer issues

• Low boiler pressure

• Air trapped in the system

• Motorised valve failure (system/regular boilers)

• Diverter valve failure (combi boilers)

Safe Checks You Can Do

Thermostat & controls

• Ensure the thermostat is set above room temperature

• Check heating and hot water modes are enabled

• Replace batteries in wireless thermostats

Timer / programmer

• Confirm heating and hot water schedules are active

• Check for resets after power cuts

Boiler pressure

• Check the gauge (should be 1.0–1.5 bar when cold)

• Top up only if confident and following the boiler manual

Radiator valves

• Ensure valves are fully open

• Uneven heating may indicate air or balancing issues

When to Call an Engineer

• No heating and no hot water after basic checks

• Repeated pressure loss

• Suspected internal valve faults pasted

2. Low Boiler Pressure

Symptoms

• Pressure below 1 bar

• Boiler locking out or cutting off

• Heating works briefly then stops

Common Causes

• Small leaks in radiators or pipework

• Recently bled radiators

• Faulty pressure relief valve (PRV)

• Expansion vessel failure

Safe Checks

• Inspect visible pipework and radiators for leaks

• Check pressure relief pipe outside for dripping

• Carefully top up pressure following manufacturer instructions

Call an Engineer If

• Pressure drops repeatedly

• No visible leaks but pressure loss continues pasted

3. Boiler Keeps Turning Off or Locking Out

Symptoms

• Boiler shuts down shortly after starting

• Frequent resets required

• Error codes or flashing lights appear

Possible Causes

• Low pressure

• Sludge or circulation issues

• Overheating due to poor flow

• Sensor or thermostat faults

• Flue or condensate issues

Safe Checks

• Confirm correct pressure

• Bleed radiators if air is present

• Inspect condensate pipe during freezing weather

Engineer Required When

• Lockouts repeat

• Loud banging or kettling noises occur

• Internal circulation faults are suspected pasted

4. Frozen Condensate Pipe (Very Common in Winter)

Condensing boilers produce condensate that drains via a plastic pipe, often routed outside. In freezing temperatures, this pipe can freeze and block.

Symptoms

• Boiler shuts down in cold weather

• Condensate or flame-failure fault codes

• Gurgling sounds

Safe Thawing Method

⚠️ Only attempt if safe to access.

• Locate the external plastic pipe

• Pour warm (not boiling) water over frozen sections

• Reset the boiler once thawed

Prevention

• Insulate external pipework

• Ask an engineer to improve routing or pipe size if recurring pasted

5. Radiators Not Heating Properly

Common Symptoms

• Cold at the top → trapped air

• Cold at the bottom → sludge

• Uneven room temperatures

Safe Checks

• Bleed radiators

• Ensure radiator valves are open

• Gently balance the system

Call an Engineer If

• Sludge is suspected

• System hasn’t been flushed for years pasted

6. Strange Noises (Banging, Whistling, Kettling)

Possible Causes

• Air in the system

• Limescale in the heat exchanger

• Sludge build-up

• Loose pipework

Safe Checks

• Bleed radiators

• Check pressure

• Inspect visible pipe supports

Engineer Needed When

• Kettling persists

• Loud banging occurs on start-up or shutdown pasted

7. Boiler Leaks

Symptoms

• Water beneath boiler

• Dripping joints

• Pressure loss

⚠️ If water is leaking from inside the boiler casing, do not remove the cover.

Call an Engineer Immediately For

• Internal boiler leaks

• Continuous discharge from pressure relief pipe

• Fast pressure loss with visible leaks pasted

8. Ignition or Pilot Light Failure

Symptoms

• Boiler won’t fire

• Clicking with no flame

• Ignition or flame-failure error codes

Safe Checks

• Check other gas appliances

• Attempt one reset only

🚨 If you smell gas: turn off the supply, ventilate the property, and call the emergency gas number immediately pasted.

9. Boiler Error Codes & Warning Lights

What You Can Do

• Note the exact error code

• Check the boiler manual

• Verify pressure, controls, power, and condensate

Call an Engineer If

• Codes repeat

• Code relates to gas, sensors, pump, or flame detection pasted

10. Preventing Boiler Problems

Annual Boiler Servicing

• Safety inspections

• Component cleaning

• Performance checks

• Warranty protection

System Protection

• Corrosion inhibitor

• Magnetic/system filters

Regular Home Checks

• Monthly pressure checks

• Listen for unusual noises

• Insulate condensate pipe

Prevention greatly reduces breakdown risk and repair costs pasted.

Final Advice from GAS TECH PLUMBERS LTD

Understanding common boiler symptoms allows you to:

• Resolve simple issues safely

• Communicate faults clearly to engineers

• Prevent minor problems becoming major breakdowns

👉 If it involves gas, flame, internal components, or removing the boiler casing — it is always a job for a qualified professional.

Need Professional Boiler Help in Lancashire & Greater Manchester?

📍 Serving: Burnley, Blackburn, Preston, Bolton, Bury, Oldham & surrounding areas📞 Call: 01282 914044🌐 Website: www.gastechplumbers.co.uk

We provide:

• Boiler repairs

• Boiler installations

• Annual boiler servicing

• Landlord Gas Safety Certificates (CP12)

• Full plumbing services