Questions and answers
Boiler, gas and CP12 questions answered
Straight answers to the questions people in Telford, Shropshire and across the UK ask most about boilers, gas safety, landlord certificates and commercial gas.
Boiler repair
When the boiler stops, leaks, loses pressure or shows a fault code.
- Why does my boiler keep losing pressure and need topping up every week?
- What pressure should my combi boiler be at, and how do I top it up?
- My radiators get hot but there is no hot water from the taps. What is wrong?
- My boiler stopped in freezing weather and shows a fault. Is it the condensate pipe?
- My boiler is showing a fault code. What does it mean and can I reset it?
- Water is dripping from underneath my boiler. Is it safe to keep using it?
- Why is my boiler making a loud banging or kettling noise?
- Why are my radiators hot at the top and cold at the bottom?
Show all 62 boiler repair questions
- Why does my boiler keep switching on and off every few minutes?
- Is it worth repairing a 10 to 15 year old boiler, or should I replace it?
- An engineer capped off my boiler as unsafe. What happens now?
- I can smell gas near my boiler. What should I do?
- I rent my home. Who is responsible for fixing the boiler?
- My boiler has stopped working. What should I check first?
- Why is my boiler display completely blank?
- My boiler keeps tripping the electrics. What should I do?
- My prepayment meter has credit but the boiler still will not light. Why?
- Why does my boiler make a gurgling noise when it tries to light and then lock out?
- How do I thaw a frozen condensate pipe?
- How can I stop my condensate pipe freezing every winter?
- Why does my boiler pressure go up when the heating is on?
- My boiler pressure keeps rising even when the boiler is off. What causes that?
- Water is dripping from a small copper pipe outside. Is that my boiler?
- What is an expansion vessel on a boiler?
- Can I recharge my boiler's expansion vessel myself?
- Why are my radiators cold at the top and warm at the bottom?
- Only one or two radiators are not heating. What could be wrong?
- How do I bleed a radiator safely?
- Do I need to top up the boiler after bleeding radiators?
- Why does my boiler need a condensate pump?
- Why does my combi hot water go hot then cold?
- Why does my combi only give hot water when I fully open the tap?
- My combi boiler is not doing heating or hot water. What is the likely cause?
- Why is my boiler making a high-pitched whistling noise?
- Why are my pipes banging when the heating comes on?
- I see green or white crust around a radiator valve. Is that a problem?
- Do I need to keep my heating on when I go away in winter?
- Why does my boiler fire up then cut out after a few seconds?
- My heating is on but the house never gets warm. Why?
- What flow temperature should I set on my combi boiler?
- How do I find the model and serial number of my boiler?
- How can I tell how old my Worcester Bosch boiler is?
- What is a GC number on a boiler?
- What is a filling loop?
- What is a diverter valve in a combi boiler?
- What does the circulating pump do in a heating system?
- What does balancing radiators mean?
- Should I use radiator leak sealer?
- What information should I give when booking a boiler repair?
- Can an engineer tell if my gas supply is low at the boiler?
- Can I drain my central heating system myself?
- What causes an airlock in a heating system?
- What does the red zone on my boiler pressure gauge mean?
- My boiler pressure gauge reads zero. Is the gauge broken?
- Can I paint my radiators?
- Why is one radiator always hotter than the rest?
- What does frost protection on my boiler do?
- Can I fit a new radiator myself?
- Can CombiCert repair a boiler brand it does not install?
- Why has my boiler lost pressure after an engineer visit?
- What is the hot water flow sensor in a combi?
- What is a plate heat exchanger in a combi?
Boiler servicing
What a service is, how often, what it costs and boiler cover.
- How often should a boiler be serviced?
- Is it really worth paying for a boiler service every year?
- How much does a boiler service cost in Telford?
- What should a proper boiler service include?
- What is the difference between a standard service and a full strip down service?
- Can you service an LPG boiler?
- Is boiler cover worth it, or should I just pay for a service and repairs?
- Should I get the boiler and gas checked when buying a house?
Show all 18 boiler servicing questions
- How do I check an engineer is really Gas Safe registered?
- What causes sludge in central heating systems?
- What is a flue gas analyser and why is it used on a service?
- Will skipping a service void my boiler warranty?
- How long does a boiler service take?
- What questions will an engineer ask before a service?
- Is the condensate trap cleaned during a service?
- What is corrosion inhibitor and does my system need it?
- Should my boiler be serviced before winter?
- What is a Benchmark checklist for my boiler?
New boiler installs
Choosing, sizing, moving and paying for a new boiler.
- What affects the price of a new boiler?
- Should I get a combi or a system boiler?
- What size boiler, in kW, do I need?
- Which boiler brand is best: Worcester Bosch, Baxi, Ideal or Viessmann?
- Can I swap my old tank system for a combi boiler?
- Can you take out a back boiler and fit a modern boiler?
- Can my boiler be moved to another room or into the loft?
- How long does it take to fit a new boiler?
Show all 26 new boiler installs questions
- Do I need a power flush before a new boiler is fitted?
- Is a free boiler under the ECO4 grant scheme legitimate?
- I am worried my new boiler was not fitted safely. What can I do?
- What is a powerflush?
- What does a magnetic system filter do?
- What is the difference between a combi, system and regular boiler?
- What happens to my hot water cylinder if I get a combi?
- Can I keep my cylinder but get rid of the loft tanks?
- Will converting to a sealed system cause leaks?
- Does a new boiler need a filter and system clean?
- Do I need to register a new boiler installation?
- Is my mains water good enough for a combi boiler?
- What is an unvented hot water cylinder?
- How do I make a warranty claim on my boiler?
- How do I know if my boiler is condensing?
- Can I box in my boiler?
- Does my heating need a bypass valve?
- How do I prepare for a boiler installation?
Heating controls and radiators
Thermostats, programmers, valves, radiators and hot water cylinders.
- What is a Y-plan heating system?
- What is an S-plan heating system?
- How do I know if I have a Y-plan or S-plan system?
- My heating works but I have no hot water from my cylinder. What could it be?
- My hot water works but the heating will not come on. What should I check?
- Why does my boiler keep firing even when the heating is off?
- What does the cylinder thermostat do?
- What does a programmer do on a heating system?
Show all 20 heating controls and radiators questions
- My room thermostat is wireless. Why has the heating stopped?
- My Hive thermostat shows heating on but the boiler is not firing. What now?
- Can a faulty programmer stop my combi boiler working?
- Can I have two heating zones with a combi boiler?
- What does a thermostatic radiator valve do?
- What is a smart thermostat and will it work with my boiler?
- What is a lockshield valve?
- What is a motorised valve and how do I know it has failed?
- Why does my hot water run cold after a few minutes on a cylinder system?
- Can my boiler work if the room thermostat batteries are flat?
- Why does my boiler not respond to the programmer at all?
- What should I check if my heating comes on at the wrong times?
Gas safety and carbon monoxide
Gas smells, carbon monoxide alarms, flues and staying safe at home.
- How do I check whether my gas supply is the problem?
- Is it safe to keep pressing the reset button on my boiler?
- What should I do if my carbon monoxide alarm goes off?
- Where should a carbon monoxide alarm go?
- Is it legal for me to do my own gas work?
- Can I take the cover off my boiler to look for a fault?
- Why does my boiler fuse keep blowing?
- What is a tightness test on gas pipework?
Show all 18 gas safety and carbon monoxide questions
- Is it normal for my boiler to make white steam outside?
- What does it mean if the flame on my gas hob or fire is yellow or orange?
- What are the symptoms of carbon monoxide poisoning?
- How do I turn off the gas supply in an emergency?
- What is a fused spur for my boiler?
- What is a pressure relief valve on a boiler?
- My unvented cylinder pipe is dripping outside. What does that mean?
- Why does my boiler smell of burning?
- Is it safe to use my boiler if the casing is damaged?
- Should my boiler be on a separate electrical circuit?
CP12 and landlords
Landlord gas safety records, tenants, CO alarms and the law.
- Do landlords legally need a gas safety certificate (CP12)?
- How long does a landlord gas safety certificate last?
- When must a landlord give tenants a copy of the gas safety certificate?
- Does the landlord gas safety check cover the gas hob and cooker as well as the boiler?
- Is a landlord gas safety check the same as a boiler service?
- What can a landlord do if a tenant refuses access for the gas safety check?
- Do landlords have to fit a carbon monoxide alarm near a gas boiler?
- Do I need a CP12 for an HMO, a lodger or a holiday let?
Show all 22 cp12 and landlords questions
- My landlord gas safety certificate has expired. What should I do?
- Do I need a gas safety certificate to sell my house?
- How can a tenant check a gas safety certificate is genuine?
- What is a CP12 certificate?
- What happens if my rental property fails a gas safety check?
- Does a tenant's own gas cooker need a landlord check?
- How long should I keep landlord gas safety records?
- Can tenants reset or top up the boiler themselves?
- Why do landlords need a CO alarm in rental properties?
- Can a gas safety check be done when the tenant is not home?
- Does a holiday let need a gas safety record?
- Does a gas safety check include the gas meter?
- What if my tenant reports a gas smell?
- Can a landlord gas safety record be issued without checking every appliance?
Commercial heating and gas
Catering kitchens, interlocks, tightness tests, plant rooms and LPG.
- Does a restaurant or takeaway need a commercial gas safety certificate?
- Does my commercial kitchen need a gas interlock?
- When does a business need a gas tightness test?
- In a rented commercial unit, who is responsible for the gas safety?
- Can a catering van or food trailer using LPG get a gas safety certificate?
- How often should a commercial boiler be serviced?
- What is a prefabricated plant room?
- How do I get a price for commercial gas or heating work?
Show all 17 commercial heating and gas questions
- Who can work on commercial boilers and plant rooms?
- What should a facilities manager check before an engineer visits a plant room?
- Does CombiCert do commercial gas work?
- What are commercial catering gas interlocks?
- What records should a business keep for gas equipment?
- What does a commercial plant room service involve?
- What should I do if a commercial boiler shows a lockout?
- Does a commercial kitchen need a CO alarm?
- What is a pressurisation unit in a plant room?
About CombiCert
Who we are, where we work, prices and how to book.
- Who is CombiCert?
- Who runs CombiCert?
- Where is CombiCert based and which areas do you cover?
- What are CombiCert's opening hours?
- What are CombiCert's prices?
- What kind of commercial clients has CombiCert worked for?
- What are CombiCert's company and VAT details?
- How do I book a boiler service, repair or CP12 with CombiCert?
No questions match that search. Try a shorter word, or call 07393 220694.
Need an engineer rather than an answer?
CombiCert Ltd, Gas Safe registered 621146, The Old School House, Park Lane, Telford, Shropshire TF3 4TG. Open Monday to Saturday 08:00 to 19:45, closed Sunday. Email hello@combicert.co.uk.
Smell gas? Call the National Gas Emergency Service on 0800 111 999.
These answers are general information, not a substitute for an on-site check by a Gas Safe registered engineer.