Published: September 19, 2026 · By Absolute Plumbing & Heating Booking an oil boiler service in Exeter once a year is one of the simplest ways to keep your heating reliable, safe and economical. Many homes across Exeter and rural Devon still run on oil — from Grant and Worcester Bosch to Warmflow and Firebird — and, unlike gas, an oil boiler burns a fuel that leaves soot and deposits behind. Skip the annual service and efficiency quietly drops, running costs creep up, and small faults turn into breakdowns on the coldest day of the year. This guide explains exactly what a proper service involves, the warning signs to watch for, honest pricing, and why it pays to use a local, experienced engineer. Why annual oil boiler servicing matters in Exeter & Devon homes Oil boilers work hard through a long Devon heating season, and they are less forgiving than gas when maintenance is neglected. As the nozzle wears and the combustion drifts out of adjustment, the boiler burns oil less cleanly. That means more soot on the heat exchanger, more oil used for the same warmth, and a greater chance of a lockout leaving you without heat or hot water. The benefits of an annual service Lower running costs from clean, correctly set combustion Fewer breakdowns and winter emergency call-outs A safer boiler, with combustion and flue checked properly Longer boiler life — deposits are removed before they cause damage Most manufacturer warranties require a documented annual service When to book Ideally in late summer or early autumn, before the heating goes on daily Roughly 12 months since the last service — keep the paperwork Straight away if you have noticed any of the warning signs below Before you top up a big oil delivery, so you are not wasting fuel Removing and cleaning the baffles inside the combustion chamber on a routine service in Exeter. Soot build-up here is exactly what pushes fuel bills up. What's included in an oil boiler service A thorough oil boiler service is far more than a quick visual check. It involves stripping down the burner, cleaning the boiler internally, and using a flue-gas analyser to prove the combustion is set correctly before the job is signed off. Here is what a full service on your boiler should cover: A proper oil boiler service checklist Burner & combustion: Clean or replace the oil nozzle Check and set the electrodes and spark gap Inspect and clean the photocell / flame sensor Set combustion and measure it with a flue-gas analyser Check the burner pressure and fan Boiler, oil supply & safety: Inspect and clean the heat exchanger and baffles Replace the oil filter and check for leaks Check the fire valve and oil line Inspect seals, gaskets and the flue Carry out full safety checks and record the readings The heat exchanger and baffles are the parts that take the most punishment. Over a year they collect a layer of soot that acts like a blanket, stopping heat reaching the water and forcing the boiler to burn more oil. Cleaning them back to bare metal — as shown in the photo at the top of this page — is one of the most valuable parts of the service. The burner removed and stripped down. The nozzle, electrodes and photocell are all checked and the combustion is re-set and measured with a flue-gas analyser. What we found during this Grant oil boiler service in Exeter Every job is different, and this one is a good example of why an annual service is about more than just cleaning. This was a Grant oil-fired combi boiler in Exeter, and while the combustion side stripped down and cleaned up well, the engineer — OFTEC-trained, with over 10 years' oil boiler experience — found four separate faults that needed putting right. Here is an honest, first-hand account of exactly what was wrong and why each part had to be dealt with. The Grant oil-fired combi boiler opened up for its annual service in Exeter, ready for inspection. 1. Heat-damaged baffle (rope) seal The baffles sit inside the combustion chamber and force the hot combustion gases to travel the long way round the heat exchanger, so as much heat as possible is passed into the water rather than shooting straight up the flue. Around these baffles runs a fibreglass rope seal. Its job is to seal the combustion chamber and flue-way so the gases are guided correctly over the baffles and heat exchanger, instead of leaking out or bypassing them. On this Grant boiler the rope seal had become heat-damaged through years of use — the fibreglass had hardened, frayed and lost its spring, so it could no longer seal properly. Once a rope seal is heat-damaged like this it cannot be repaired; it has to be renewed so the combustion chamber is sealed correctly again and the boiler burns efficiently and safely. The baffles and their fibreglass rope seal. Years of heat had hardened and frayed the seal, so it needed renewing to keep the combustion chamber sealed correctly. 2. Scaled-up, leaking water flow switch Because this is a combi boiler, it heats domestic hot water on demand rather than storing it in a cylinder. The water flow switch is the part that detects when you open a hot tap — it senses the flow of water and tells the boiler to fire up for hot water (the DHW demand). Without it working correctly, the boiler cannot reliably know when to heat your water. On this boiler the flow switch had a build-up of limescale / scaling and had begun to leak. Scaling stops the switch operating reliably, and once a component like this is scaled up and weeping it is not something you patch — the sensible, lasting fix is to replace it with a new flow switch so hot water fires correctly and the leak is stopped for good. The water flow switch had scaled up and started to leak, so it was replaced rather than repaired. 3. Fibreglass door seal re-bedded with heat-resistant mastic The fibreglass door seal keeps the combustion chamber door airtight so combustion gases cannot escape past it. On this boiler the seal had worked loose and needed bedding back into place. To do that properly the engineer used heat-resistant mastic — a sealant designed to cope with the high temperatures inside the boiler — to reseat the fibreglass seal so the door closes tight and airtight against the combustion gases once more. 4. Failed automatic air vent (AAV) The automatic air vent (AAV) sits on the boiler's waterways and does an important job automatically: it clears trapped air out of the waterways and heat exchanger so the water can circulate freely. Air naturally works its way into a heating system over time, and the AAV lets it escape without anyone having to bleed it by hand. On this Grant combi the air vent had stopped releasing air from the boiler's waterways. When an AAV fails like this, trapped air is left with nowhere to go — which causes gurgling and knocking noises, poor circulation and reduced efficiency, and over time can lead to hot-spots and corrosion. It cannot be freed off reliably, so it was renewed with a new automatic air vent to let the system clear itself of air again. Faults like these are exactly what an annual service is for — caught early, put right properly, and explained to you clearly before any parts are fitted. None of these four faults were dramatic on their own, but left alone they would have quietly cost the homeowner money and reliability — a leaking flow switch, air-locked waterways and a poorly sealed combustion chamber all pull an oil boiler away from running efficiently. Every part that needed replacing was explained and agreed before it was fitted. Signs your oil boiler needs servicing or attention Oil boilers usually give you plenty of warning before they fail. If you notice any of the following, it is worth booking a service or repair sooner rather than later: Sooting or black marks around the boiler or flue — a sign of poor combustion The boiler locking out and needing to be reset repeatedly A strong smell of oil or fumes when the boiler is running Rising oil use without a change in how much heating you are using Rumbling, banging or unusual noise from the boiler or burner Leaks, drips or corrosion around the boiler, valves or pipework That last point matters more than people think. Small leaks and corroded valves are common on older oil systems, and they often only come to light during a service. The automatic air vent pictured below had corroded and started to weep — left unchecked it would have dropped the system pressure and could have caused water damage. A corroded, leaking automatic air vent spotted during a service in Exeter — exactly the kind of fault an annual check catches before it becomes a bigger, more expensive problem. How much does an oil boiler service cost in Exeter? Every home and boiler is a little different, so the honest answer is that pricing starts from a fixed £65 callout and is quoted clearly before any work begins. The exact figure for a full service depends on your boiler type, its condition, and where you are — but you will always know the price up front, with no surprises added afterwards. What affects the price Whether the nozzle, oil filter or any seals need replacing How much cleaning the heat exchanger and baffles need Any repairs found during the service, such as a leaking valve Your location within and around Exeter Any parts or additional repairs are always discussed and agreed with you before they are carried out. Why choose a local Exeter engineer Oil boilers are a specialist job, and it makes a real difference having someone local who knows them inside out. Absolute Plumbing & Heating has been established since 2015 as a trusted local Exeter engineer, and the owner is OFTEC-trained with over 10 years' oil boiler experience, trained by Grant UK at their training centre. That hands-on background means your service is done properly — combustion set with a flue-gas analyser, not by eye — and any faults are spotted early. For gas work, we are fully Gas Safe registered. We cover Exeter and the surrounding villages, including Heavitree, St Thomas, Pinhoe and Topsham, as well as the wider Devon area. Being local means we can get to you quickly, and we build long-term relationships with customers who come back to us year after year for their annual service. At a glance OFTEC-trained, 10+ years' oil boiler experience, trained by Grant UK Gas Safe registered for gas boiler work Established since 2015 — a trusted local Exeter engineer Covering Exeter, Heavitree, St Thomas, Pinhoe, Topsham and across Devon Clear, honest pricing from a fixed £65 callout Frequently Asked Questions How often should an oil boiler be serviced? Once a year. Oil is a dirtier fuel than gas, so the nozzle, filter and heat exchanger need attention every 12 months to keep the boiler efficient and safe. An annual service is also usually a condition of keeping your manufacturer's warranty valid. How long does an oil boiler service take? A full oil boiler service usually takes around an hour to 90 minutes, depending on the boiler and how much cleaning it needs. Stripping the burner, cleaning the heat exchanger and baffles, and setting the combustion properly all take a little time — it is not a job to rush. Are you OFTEC registered or Gas Safe registered? For gas work we are fully Gas Safe registered. For oil, the owner is OFTEC-trained with over 10 years' oil boiler experience, having sat the OFTEC qualification with Grant UK. We believe in being straight with customers, so it is worth noting that OFTEC registration itself has since lapsed — the training, experience and standard of work remain exactly the same. Which areas around Exeter do you cover? We cover Exeter and the surrounding area, including Heavitree, St Thomas, Pinhoe and Topsham, plus villages across Devon such as Crediton, Cullompton and Broadclyst. If you are not sure whether you are in range, give us a call and we will let you know. Book your oil boiler service in Exeter A yearly service keeps your oil boiler safe, efficient and reliable — and gives you peace of mind before the winter. To book your oil boiler service in Exeter, or if you have noticed any of the warning signs above, get in touch with Absolute Plumbing & Heating. Ready to book your annual oil boiler service? Call today for honest advice and clear pricing from an OFTEC-trained local engineer. Call 07766 501664 Or book your oil boiler service in Exeter online.