We replace failing oil supply lines in the correct materials, properly protected and ducted where buried, with isolation and a compliant fire valve. Persistent lockouts that clear after bleeding are very often the line rather than the burner.
Why lines fail
- Buried plastic perishes. Unprotected plastic line in the ground degrades, and a buried joint that weeps is invisible until the ground tells you about it.
- Copper corrodes, particularly where it sits in wet soil or against a rough edge that has abraded it through years of thermal movement.
- Joints work loose with expansion and contraction, letting air in before they let oil out.
- Flexible connections perish. They have a finite life and they are a common source of oil smells near the boiler.
- Old lines were run to different expectations, frequently with joints below ground, no ducting and no protection where they pass under drives.
- Damage from other work – a drive relaid, a fence post driven in, a drainage trench dug.
A line that is drawing air causes intermittent lockouts that clear after bleeding. That happens long before the line loses enough oil to show on the ground, which is why persistent unexplained lockouts are worth investigating as a fuel line problem rather than replacing burner components.
The signs
| Symptom | What it suggests |
|---|---|
| Intermittent lockouts that clear after bleeding | Air being drawn in at a joint, seal or high point. The classic sign |
| Boiler will not restart after a delivery | Air in the line, and possibly a marginal joint that only leaks air under suction |
| Smell of oil along the pipe route | A weeping joint or a failing flexible connection |
| Staining on the ground along the route | A buried line that is weeping. Stop using it and call |
| Dead or discoloured vegetation over the route | Oil in the soil |
| Repeated filter blockages | Frequently a tank problem, occasionally debris from a degrading line |
| Works in summer, struggles in winter | Waxing in a badly routed exposed run, or a marginal restriction |
The first row is the important one. A great deal of money is spent on control boxes and pumps for faults that were a weeping seal or a high point in the run – see oil boiler not firing.
How a replacement line is run
Above ground
Copper or steel, properly clipped, with expansion allowed for on long runs. Ordinary plastic is not acceptable for an exposed above-ground run – it is not fire resistant and it degrades in sunlight. A short purpose-made flexible connection at the burner is normal and correct.
Below ground
Plastic-coated copper or purpose-made plastic oil line in a duct, at a sensible depth, with no joints below ground wherever it can possibly be avoided. Where the line crosses a driveway or hardstanding it is ducted, so it can be replaced in future without excavation.
Through the building
Sleeved and sealed where it passes through walls or floors, both for fire and to stop the pipe being abraded by the structure. Runs inside kept short and visible where possible – buried oil pipe in a screed is a problem waiting to happen.
What goes on it
A valve at the tank outlet, a filter with a replaceable element somewhere you can kneel next to it, a valve at the appliance, and a remote-sensing fire valve outside the building before the line enters – see fire valve replacement.
Single-pipe, two-pipe and de-aeration
Most modern installations are single-pipe with the tank above the burner, which is simpler and avoids a return line. Two-pipe systems exist where the tank sits below burner level, and they bring their own considerations – not least that a two-pipe pump converted to single-pipe without removing the bypass plug will damage itself. It is a detail that gets missed on burner changes.
Where an installation suffers repeatedly from air – long runs, a tank below burner level, or a line with an unavoidable high point – a de-aerator is frequently the right answer. It separates air out of the fuel and returns it to the tank rather than letting it reach the pump, and it converts a two-pipe requirement into a single-pipe run.
It is not a routine fitting and it should not be added speculatively. Where the symptom is persistent air and the route cannot be improved, it is the fix rather than another service visit.
What it involves
- Survey the existing routeWhere it runs, what it is made of, where the joints are, and what access there is.
- Agree the new routeShorter and better protected where possible. Ducting under anything that will be dug up in future.
- Recover and isolateTank valve closed, existing line drained into a container – oil in a line is still oil and it is not going on the ground.
- Install the new lineCorrect materials, clipped or ducted, sleeved through structure, with no buried joints.
- Fit valves, filter and fire valveIsolation at both ends, accessible filter, compliant fire valve outside the building.
- Pressure test and bleedLine proven, burner bled and primed.
- RecommissionCombustion checked with an analyser, readings recorded, and the boiler left working.
- Deal with the old lineRemoved where practical, or made safe and capped where it is buried under something that cannot reasonably be lifted.
Oil in the soil is a different and far more serious matter than a pipe replacement, and it can involve the Environment Agency and your insurer. If you can see or smell oil in the ground, tell us when you call. Do not dig it over and do not hose it down – both make it worse.
Boiler locking out intermittently and clearing after a bleed? The line is the first thing to eliminate, before anybody replaces a control box.
Questions we get asked about this
Does my oil line need replacing?
If it is causing air ingress, weeping, or staining the ground, yes. If it is sound and correctly installed, no – age alone is not the test. Persistent unexplained lockouts are the usual reason for looking at it.
Can I use plastic pipe for an oil line?
Not for an exposed above-ground run. Purpose-made plastic oil line has a place buried and ducted, installed to the manufacturer’s requirements. Ordinary plastic plumbing pipe has no place in an oil system anywhere.
My line is buried and I do not know where it runs.
Not ideal. If it is sound it is working; the risk is that a buried leak is invisible until it has contaminated ground, and that future work can hit it. When we renew a line we duct it, so its route is known and it can be replaced without digging.
Do I need a de-aerator?
Only if you have a problem that calls for one – persistent air, a tank below burner level, or a long awkward run. It is not a routine fitting.
Should the line be replaced when the boiler is?
Not automatically, but it should be properly inspected, and flexible connections should be renewed as a matter of course. A twenty-year-old line feeding a new appliance is where a lot of early-life boiler problems actually come from.
What happens to the old buried line?
Removed where practical. Where it runs under something that cannot reasonably be lifted, it is drained, made safe and capped, and its position recorded.
What happens when you call
Call and describe it
You speak to an engineer, not a call centre. Most jobs can be narrowed down on the phone.
We look at it properly
A real diagnosis before a price, and a straight answer if it is not worth doing.
A written quote
Itemised, so you can see what you are paying for.
The job, and the paperwork
Certificates where the work needs them, and what will need attention next.
Where we do this work
Across Norwich and the whole of Norfolk. If you are on the edge of the county, call and ask — we will tell you honestly whether we are the right people.
- Norwich
- Wymondham
- Dereham
- Attleborough
- Aylsham
- North Walsham
- Cromer
- Diss
- Loddon
- Long Stratton
- Watton
- King's Lynn
Need this doing?
Call and describe the problem — you will speak to an engineer, not a call centre. Written quotes, no estimates over the phone.