Low Boiler Pressure: Causes and How to Top It Up
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Heating · 4 min read

Low Boiler Pressure: Causes and How to Top It Up

By the Sureway team

5 Star Rated46 five star Google reviews
Gas SafeRegistered and fully insured
Since 1964Over 60 years in Warwickshire
Baxi AccreditedUp to 12 years on selected boilers
30 Mile RadiusCovering all around Warwick

Low boiler pressure is one of the most common reasons a combi boiler stops providing heating or hot water. The good news is that it is often a quick fix.

What Should the Pressure Be?

Most boilers should sit between 1 and 1.5 bar when the heating is off. The gauge is usually on the front or underneath the boiler. If it drops below 1 bar, many boilers will lock out and show a fault code.

Common Causes

  • You have recently bled your radiators, which releases water from the system
  • A small leak somewhere on the pipework, a radiator valve or the boiler itself
  • A faulty pressure relief valve letting water out
  • A worn expansion vessel inside the boiler

How to Top It Up

Most combi boilers have a filling loop, a braided hose or built in key underneath the boiler. With the boiler off and cool, open both valves slowly and watch the gauge. Close them when it reaches around 1.2 to 1.5 bar, then restart the boiler. Your boiler manual will show the exact steps for your model.

When It Keeps Dropping

If you need to top up the pressure more than once every few months, there is a fault somewhere. Ignoring it can lead to corrosion and bigger repairs. Check under radiators and around visible pipes for drips, and look for water on the outside pipe from the pressure relief valve.

Get It Checked

Our Gas Safe engineers can find the cause and fix it. Call 01926 310900 or book a service online. Pressure checks are part of every boiler service we carry out across Warwickshire.

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Google reviews

What Warwickshire Says About Us

46 Five Star ReviewsRead them all on Google

My late mother, began using Sureway back in 2007. They were always very responsive to emergency call outs to her LPG boiler. The engineers were particularly kind and helpful to her, especially as she became older and more frail. I will continue to use their services as I will be now be renting out her property. They have recently installed a new boiler and were quick to act when the old boiler stopped working. Thank you to Andy and the team.

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Jennifer JohnsGoogle review

Had Jamie and the team fit a kitchen for me. Access to the property was somewhat difficult as it was a flat, which made worktop installation something of a challenge given the long run required along both sides of the kitchen. The work was completed to an excellent standard with new flooring, electrical work, plastering and plumbing, with Jamie organising and scheduling all the trades to attend in order with no time wasted in between. Very happy with the final work, with all mess tidied away quickly and efficiently so as not to annoy the neighbours. Recommended

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William LeeGoogle review

Have dealt with Sureway for 40yrs Highly recommend.Professional to the core. Complicated fitting of a new boiler. Assessed, planned & installed with the utmost skill. Thank-you Cale, Austin, Brian & Andy [back at base]. This nation relies on & was built by such tradesmen.

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John GreenhillGoogle review

My 86 year old mother has used Sureways for many years (probably near 40 years)and we have always found them to be helpful. They did try to fix her 13 year old boiler but it needed replacing. They bent over backwards to get this done for her and was treated as priority. Greg, Freddie and Andy Thankyou!

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Joanne PackerGoogle review

I've now been using Sureway for a couple of years for plumbing and boiler servicing and they're excellent - professional, courteous and efficient, all for a fair price. The boiler was serviced this week by Greg who was great, he came on time, serviced the boiler including changing seals and showed me the condenser pump was broken. Came the next day to replace the pump and again he was excellent. No hesitation in recommending Sureway.

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deltic 09Google review

Sureway Heating Services have serviced my heating system for over 20 years and replaced the boiler when my old one was past repair, not a surprise as it was 25 years old! The engineers are friendly and today Greg replaced a motorised valve with no fuss. He has been with Sureway for a while and I am always pleased its him when he services our boiler every September.

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Jackie EdwardsGoogle review

I had a great experience with "Sureway Heating Services". The engineer was professional, punctual, and clearly very knowledgeable. He explained what the issue was, talked me through the solution, and completed the work efficiently and to a high standard. Everything was left clean and tidy afterwards, which I really appreciated. Honest, reliable service with excellent attention to detail — I wouldn’t hesitate to recommend "Sureway Heating Services" to anyone needing heating work done.

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Bhimashankar DukareGoogle review

I have dealt with Sureway Heating Services for over 20 years. They carry out my annual service on the gas boiler and fitted a new boiler few years ago. The engineers are always polite and professional and extremely tidy when carrying out any work.Their prices are very reasonable and the work is of a high standard. I can highly recommend Sureway Heating Services

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Margaret WilkinsGoogle review

I called out Sureway Heating Services as I had a leak in the bathroom. I had previously called out 2 other company's to rectify the leak but could not find it. Sureway heating called out and within 20 minutes traced the leak to the pan connector on the toilet. The repair was carried out by the engineer who was very polite and left everything clean on departure The engineer also protected my carpets where as the others did not. I was very happy with Sureway Heating and would recommend to anyone. 5 Stars Wayne Leamington Spa

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WayneGoogle review

Completed a long list of plumbing jobs to a high standard and at a reasonable cost. Very professional, friendly and helpful. Really impressed with Sureway Heating Services and would definitely recommend them.

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Chris BrazierGoogle review

We have used Sureway Heating many times and always had fantastic service. Today we had an outside tap fitted. The engineer was highly knowledgeable and professional and we are delighted yet again with the end result. The engineer was very polite and always took his shoes off inside the house. Everything was put back where he found it and left clean and tidy. Excellent job at a very good price. Thank you so much from Michaella and Trevor

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Michaella BlunnGoogle review

Boiler replacement arranged and all work carried out within a week. All very professional and accurate. Excellent

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Don ClarksonGoogle review

We had a problem with the central heating when we tried to turn it on this year. We contacted Sureway, who we’ve always used, when Craig came out he diagnosed the problems and had it fixed within a couple of hours. Excellent service.

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Robin HoskingGoogle review

We called Sureway Heating Services to quote for our new boiler, their response was very quick and the quote was very reasonable so we decided to go with them. I have to say the engineers worked very hard and kept us informed of where they were going to work next which made the whole experience easier. They were very tidy when working and when they left each day i would not have known they had been here. When the installation was finished the head engineer walked me through the job and explained how everything work which i thought was a very nice touch. All in all i was very happy with the finished job and i would highly recommend this company.

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pauline finchGoogle review

Sureway (who have been our heating engineers for decades) just replaced our ancient cast iron boiler. Their estimate was detailed and thoughtful and reasonable (I did ask for several others from competitors). The work was carried out perfectly. The lads who did it (we're in our 70s - everyone still in work seems like a lad to us) were prompt and meticulous and happy to explain all the aspects of the work to us. It was completed on time and on budget. We would recommend them without reservation.

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Tom HerveyGoogle review

Replacement of ageing boiler and radiators carried out in a very professional manner by the team. Great advice, no fuss, no mess, no shortcuts and a pleasure to work with. Thank you.

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Mick MooreGoogle review

My boiler stopped working yesterday for no reason so i called these guys out, Within 24hours they had attended, got the part and had the boiler back up and running. The bill was also very reasonable, i would highly recommend.

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PhillGoogle review

Our heating packed up overnight , I called and an engineer (Steve) was able to turn up and quickly diagnose a boiler fan. He managed to find a new one and fit it within 4 hours of my first call, which was fantastic service. Have used for years and will continue to use Sureway.

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Richard TGoogle review

We recently had a new boiler fitted and we used Sureway Heating as we have been customers for 30 years. They installed our first boiler, a Potterton gravity system with the hot water tank in the airing cupboard and a header tank in the loft. So 30 years later it was a big job to convert to a combi condensing system and have all the above removed. To make the job even more labour intensive the new boiler required a bigger gas intake pipe from the meter in the garage to the kitchen. We have to say Cale, our gas fitter, and his mate, Fred, worked really hard during the four days they were with us and did a really good job. They were both respectful and personable at all times. When they finished they left our home clean and tidy. We would like to thank them and recommend them to anyone considering a new boiler installation.

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Richard JonesGoogle review

Martin and Jack have just completed the replacement of our twenty-two year old boiler (also installed by Sureway). Prompt, courteous, considerate and hardworking, they were exemplary, and a pleasure to have working in the house. The installation was completed in the allotted two days and to budget with the minimum of fuss. I would recommend them wholeheartedly. Margaret

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Margaret RushtonGoogle review

Our central heating packed up Friday night so left s message for Monday. Although booked up and not offered guaranteed slot till Thursday, we were fitted in back end of Monday afternoon. We needed a new pump and after bit of a struggle to shift the old one, we had a new one and working heating in about an hour and a half. Thanks do much. Reliable, nice people. Tidy professionals. We have relied on Sureway for many years and never been let down.

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richard rossGoogle review

Excellent service of fitting new boiler and sundries over 3 days. The 2 young men who did the work - worked non stop, and were very accommodating when questions were asked, as well as always polite. No complaints, and we recommend Sureway, Leamington Spa.

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sally bullockGoogle review

Used Sureway for a few years now and it always a really good service, the engineers are always polite and leave the place tidy. Would highly recommend.

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Teven 37Google review

Sureway engineers and office staff very kind and helpful, replacing broken boiler in 2 days for elderly relative. Smart, friendly, cleaned up afterwards really well, and no worries with them being in the house. Really pleased with new boiler and timer.

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V DixonGoogle review

Thank you to Cale and Freddie for doing a very tidy and efficient job in replacing all my radiators on Tuesday! A very professional service, as always, from Sureway Heating!

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Ema UshiodaGoogle review

We had a leak coming from a bedroom radiator. We called Sureway, they attended at the agreed time, diagnosed the problem quickly and carried out the repair efficiently. At all times Martin and Jack were polite and professional. Any future plumbing needs we have will be carried out by Sureway.

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Keith WardGoogle review

Very impressed with the team from Sureway Martin and Tom who fitted a new boiler for us when our old one gave up the ghost after 20+ years. Professional diligent and courteous. Martin, the more experienced engineer, kept us fully informed throughout - highly recommend.

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DavidGoogle review

Sureway did a superb job replacing our boiler, hot water system, controls, and radiators. They were quick and efficient, cost effective, and always looking to provide the most sensible solutions. I wouldn't hesitate to recommend this company. Thanks very much.

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andrew leadbetterGoogle review

Recently had a Vaillant combi-boiler fitted in a very tricky location requiring an upgrade of the gas supply and repairs / changes to the existing C/H system. Martin and Tom did a great job. Good advice on boiler selection and awkward pipe runs; always came when they said; fully explained every part of the job; cleaned up and took away scrap at the end of every day; on commissioning Martin briefed me on using the controls. Superb 5* service . Thank you Sureway and particularly Martin & Tom.

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Ian MeddomsGoogle review

Greg visited us this morning. So friendly and so helpful - answered all my questions and perfectly completed all the work we asked him to.

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Mark MitchellGoogle review

Thank you very much for coming to repair our central heating so quickly last week and for the skill and professionalism of your engineer who completed the job at minimum cost to ourselves. We have always received excellent service from your company. Peter Byrd

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Susan ByrdGoogle review

My boiler broke down over the weekend and i called Sureway heating and they came out before 12.00 pm and fixed my boiler the engineer was very polite and left every thing working . I was so happy to have my heating back on . Thank you Sureway 100% 5 stars

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pauline finchGoogle review

Chaz attended 1st class service and fan replacement Immaculate knowledge and courtesy Efficient and quick Craig also offering a first class customer service ensuring good contact with client and pursuing the job at hand Would only use this firm from now on.

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Art Lounge International T.V OFFICIALGoogle review

We had a new uprated boiler and new controls for the overall heating system installed by Martin and Jack from Sureway-a big and complicated job that they did on time and very efficiently. Always happy to answer our inevitably stupid questions patiently!

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Shaun PittGoogle review

Had new smart Thermostats fitted and gas pipe capped. Very efficient and did a great job!

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Nick ScottGoogle review

Thank you so much for your quick response to fix the heating for my elderly mother. I live a long way away so it was really appreciated. Steve

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Steve TurnerGoogle review

Used to fix a boiler fault. My parents had a similar issue two weeks later and they had an equally good experience

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Simon KeayGoogle review

Very quick response to my emergency call. Expert advice given. Not excessive cost. Why go anywhere else?

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David PattendenGoogle review

Attended rapidly and sorted my boiler very quickly, would highly recommend to anyone.

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Craig RowlandsGoogle review

Superb service - a dripping Vaillant boiler sorted out, taking two hours.

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Gervald FrykmanGoogle review

ALWAYS A GREAT SERVICE FROM THE SUREWAY TEAM - WHETHER SERVICING OUR BOILER TO REPLACING AN AWKWARD RADIATOR - ALWAYS VERY PROFESSIONAL TED LEONARD WHITNASH

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Edward LeonardGoogle review

Regular boiler service always completed quickly and professionally.

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David BrunsonGoogle review

Really professional and efficient would highly recommend!

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Zoe CoxGoogle review
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