Oil Storage Tank Regulations: OFTEC OFS T100, Bunded vs Single-Skin, Secondary Containment and EA Rules
Quick Answer: Domestic oil storage tanks in England must comply with the Control of Pollution (Oil Storage) Regulations 2001 (England) and OFTEC standard OFS T100. A bunded tank (double-skinned with integral secondary containment) is required for tanks within 10m of a watercourse, 50m of a spring/well/borehole, or in a flood risk area. Single-skin tanks are permissible elsewhere but the installation must include secondary containment measures. Tank capacity for domestic heating oil (kerosene) is typically 1,000–2,500 litres.
Summary
Oil storage is a significant environmental risk — a single domestic tank failure can contaminate watercourses, groundwater, and soil at substantial remediation cost. The regulatory framework (Oil Storage Regulations, Environment Agency guidance, and OFTEC OFS T100) sets minimum standards for tank construction, siting, secondary containment, and pipework to minimise this risk.
For oil heating engineers and groundworkers installing or replacing oil tanks, understanding these requirements is essential. The tank installation must comply with OFS T100 for OFTEC certification purposes, and the EA Oil Storage Regulations apply regardless of whether the installer is OFTEC-registered.
Key Facts
- Control of Pollution (Oil Storage) Regulations 2001 — the primary legislation for oil storage in England; applies to above-ground tanks ≥200 litres; sets requirements for secondary containment, pipework protection, and maintenance
- OFTEC OFS T100 — OFTEC's technical standard for the installation of domestic oil storage tanks; the practical standard that OFTEC-registered engineers (OFT104) must comply with; covers siting, secondary containment, pipework, and fill point requirements
- Bunded tank — a double-skinned tank where the inner tank (primary vessel) is surrounded by an outer bund; the bund provides secondary containment ≥110% of the primary tank capacity; required in high-risk locations; preferred for all new installations
- Single-skin tank — a conventional single-walled tank; legal for some locations but requires an external secondary containment bund (masonry, concrete, or pre-formed proprietary bund); less common for new installations as bunded tanks have similar cost
- Secondary containment requirement — any secondary containment (bund) must hold ≥110% of the tank's capacity; this ensures that a full-tank failure does not overflow the bund
- Siting distances — bunded tank required when:
- Within 10 metres of a watercourse (stream, ditch, drain, river, pond)
- Within 50 metres of a spring, well, or borehole used for human consumption
- In a flood risk area (Environment Agency flood zone 2 or 3)
- Within 10 metres of a loose-fill drain or soakaway
- Fire safety distances — tanks must be sited at minimum distances from: buildings with openings (windows, doors) ≥600mm; boundaries ≥600mm (or 760mm for tanks >3,400 litres); oil-fired appliance flue terminals; see OFS T100 for full table
- Fill point location — the fill point must be accessible for the delivery driver (typically within 30m of road access for a standard delivery hose); must be remote from heat sources, electrical equipment, and drains; labelled with tank capacity and fuel type
- Overfill protection — tanks must have an overfill prevention device (OPD): a float valve or electronic gauge that prevents overfilling during delivery; required on all new tank installations
- Vent pipe — tanks must have a vent pipe to atmosphere (to prevent pressure buildup); the vent outlet must be positioned away from drains, gutters, and ignition sources; typically a vertical pipe terminating 50mm above the top of the tank
- Oil supply pipework — the oil supply pipe from the tank to the boiler must be: buried where it crosses open ground (to prevent accidental damage); protected where it passes through walls; fitted with a remote-acting fire valve (heat-activated valve that closes in case of fire, preventing oil flow)
- Remote fire valve (RFV) — a thermally-actuated valve fitted in the oil supply line within 500mm of the boiler; closes automatically when the sensor (fitted above the boiler) reaches a set temperature (~95°C); required on all oil boiler installations by Part J and OFS T100
- Tank material — plastic (polyethylene or GRP) or steel; plastic tanks (typically MDPE or GRP) are now most common for domestic installations; steel tanks corrode internally over time; check condition of steel tanks before reusing
Quick Reference Table: Bunded vs Single-Skin Tank Requirements
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Try squote free →| Location | Bunded Required? | Single-Skin Acceptable? |
|---|---|---|
| >10m from watercourse, outside flood zone | No | Yes (with secondary containment) |
| Within 10m of watercourse | Yes | No |
| Within 50m of well/borehole | Yes | No |
| Flood risk area (EA Zone 2/3) | Yes | No |
| Within 10m of soakaway | Yes | No |
| Inside a building (utility room) | Bund tray required | Yes with drip tray (200L min) |
Detailed Guidance
Siting the Tank
Structural support: The tank must be supported on a firm, level base — typically a concrete pad extending at least 300mm beyond the tank footprint in all directions. The pad must be able to support the full weight of the tank plus oil (kerosene: approximately 0.8 kg/litre; a 1,200L tank full = ~960kg of oil plus the tank weight). Proprietary plastic tank legs or a frame are acceptable if rated for the full load.
Secondary containment (external bund): For a single-skin tank where secondary containment is required:
- A masonry or concrete bund, rendered and waterproof
- Capacity ≥110% of the primary tank capacity
- No drain valve in the bund base (the bund must retain any spill)
- Bund walls typically 300–400mm high
For a bunded (double-skin) tank:
- The integrally bunded tank satisfies the secondary containment requirement
- No external masonry bund required
- Verify the bund capacity rating on the tank manufacturer's specification
Oil Supply Pipework
Pipe material and routing:
- Below-ground: black MDPE (PE) or copper; burial depth minimum 350mm (where subject to traffic loading, 600mm with sand bedding and warning tape)
- Above-ground: rigid copper or MDPE; protected from mechanical damage (conduit or duct where exposed)
- No push-fit connections underground; use compression or approved PE electrofusion fittings only
Remote fire valve (RFV): The RFV is a non-resettable, thermally-actuated valve that must be fitted in the supply line within 500mm of the oil-fired appliance. The sensor (heat-sensitive phial) is positioned above the appliance. If a fire occurs and the temperature exceeds ~95°C, the valve closes, preventing continued oil flow to the fire.
After a fire valve operates, the valve must be replaced (not reset — it is single-use). This is an important customer safety briefing point.
Anti-siphon valve or two-pipe system: Where the oil tank is above the burner and the oil supply operates by gravity, an anti-siphon device or a two-pipe (Tiger loop or de-aerator) arrangement is used to prevent over-supply. Most modern single-pipe pressure-jet burner systems use a suction pump and do not need anti-siphon, but the installation manual must be followed.
Fill Point and Delivery Access
The fill point (tank filler neck) must be:
- Accessible to the delivery driver without entering the property (within 30m of the delivery vehicle access point)
- Clearly labelled: "HEATING OIL — KEROSENE" (or appropriate fuel type)
- Fitted with a lockable cap
- Away from electrical equipment, heat sources, drains, and gullies
A magnetic gauge or electronic level gauge fitted to the tank allows the customer to monitor oil level without manual dipping. Low-level alarms are available to alert when the tank is near-empty.
OFT104 Registration for Tank Installation
Installing a new domestic oil storage tank (or replacing an existing tank) is covered by OFTEC's OFT104 registration category. An OFT101-registered engineer (boiler installer) does not automatically have OFT104 scope. If a boiler engineer wants to install the tank as well, they must hold both OFT101 and OFT104 (or subcontract the tank installation to an OFT104-registered engineer).
Frequently Asked Questions
The existing tank is a single-skin steel tank, 20 years old. Does it need to be replaced?
Not automatically — but a thorough condition assessment is required. Steel tanks corrode from the inside (condensation and water accumulation at the bottom) and from the outside (soil contact). Signs of deterioration: rust weeping through the outer surface, surface pitting, seam leaks. A leaking or structurally compromised tank should be replaced. If the tank is within a siting distance that now requires a bunded tank (new regulations since it was installed), replacement with a compliant bunded tank is required.
Can the oil tank be inside a garage or outbuilding?
Yes — tanks inside a building require a drip tray with ≥200L capacity (or appropriate secondary containment). Ventilation of the building is required to prevent fuel vapour accumulation. The fill point must still be accessible from outside without entering the building for delivery purposes. The tank must be positioned away from ignition sources (boiler, electrical equipment).
Who enforces the Oil Storage Regulations?
In England, the Environment Agency (EA) is the primary enforcement body for the Control of Pollution (Oil Storage) Regulations. Local authorities also have enforcement powers. The EA can require remediation of contamination at the tank owner's expense — oil spills are expensive to clean up. Insurance may not cover pollution liability if the tank was non-compliant.
Regulations & Standards
Control of Pollution (Oil Storage) Regulations 2001 (England) — primary legislation for above-ground oil storage
OFTEC OFS T100 — OFTEC technical standard for domestic oil tank installation
Building Regulations Approved Document J — oil storage as part of oil appliance installation
Environment Agency PPGS 5 (Pollution Prevention Guidelines) — good practice guidance for oil storage (now superseded by EA guidance pages but still referenced)
Environment Agency — oil storage regulations guidance — EA guidance on compliance
OFTEC OFS T100 — oftec.org — tank installation standard
CIRIA C736 — guidance on secondary containment for oil storage
oftec registration oft101 — OFTEC registration including OFT104 tank category
building regs part j oil — Part J requirements for oil storage as part of appliance installation
oil boiler service procedure — fire valve inspection during annual service