LPG Installations: Storage, Pipework & Key Differences from Natural Gas

Summary

Around 4 million UK homes use LPG as their primary or secondary gas fuel, the majority in rural areas without mains gas supply. Working safely with LPG requires understanding the key differences from natural gas: LPG is denser than air (it sinks and can accumulate at low level in poorly ventilated spaces — a significant explosion risk), it operates at different pressures, and storage regulations are more stringent than for the gas meter boxes used for mains NG.

For Gas Safe engineers, an LPG ACS assessment (LP1 or equivalent) is a separate requirement from the NG core assessments. Engineers with NG registration only cannot legally work on LPG systems. This is commonly overlooked when a NG-experienced engineer is asked to carry out work on an LPG property.

The growth of domestic biomethane and hydrogen blend trials means that gas composition is evolving, but LPG remains the primary alternative fuel for off-grid properties and is also used in campsites, boats, and commercial catering. The storage and installation principles in this article apply primarily to static domestic propane tank installations.

Key Facts

• LPG types (domestic) — propane (C₃H₈) for outside bulk tanks (works in freezing temperatures); butane (C₄H₁₀) for portable cylinders (not suitable below ~5°C)
• Propane operating pressure — 37 mbar (domestic appliances); regulated down from tank pressure (~7 bar at 20°C) via a two-stage regulator
• Butane operating pressure — 28–30 mbar; lower vapour pressure means it won't work well in cold weather
• Calorific value (propane) — approximately 95 MJ/m³ vs NG 38.4 MJ/m³; LPG provides roughly 2.5× the energy per m³ — pipe sizes are smaller for the same kW output
• Density — LPG vapour is heavier than air (propane vapour density ~1.5 relative to air); accumulates in low points, cellars, drains — unlike NG which rises and disperses
• Gas Safe ACS for LPG — LP1 (core LPG domestic); appliance-specific categories additionally required (e.g., COCN1 for catering, or CPA1 for central heating boilers with LPG variant)
• IGEM/UP/11 — specification for domestic and similar LPG installations; the equivalent of BS 6891 for LPG
• Bulk tanks — typically 500, 1000, 1700, or 3000 litre storage capacity; owned or rented from LPG suppliers (Calor, Flogas, Countrywide, AvantiGas); 500 litre tanks most common for domestic heating
• Minimum tank distances (HSE L56 / LPGA CoP) — 500L+ bulk tank must be: 1m from non-boundary wall; 3m from openings in buildings; 3m from boundary; 7.5m from cellar openings and drains
• LPGA Code of Practice 1 — LP Gas Association publication covering design, installation, and maintenance of domestic LPG installations; the primary industry reference
• Underground tanks — permitted in some situations; requires specialist design and installation; cathodic protection may be needed; specialist contractors only
• Cathodic protection — underground metallic pipework and tanks in LPG installations may need cathodic protection to prevent corrosion; not required for above-ground copper domestic pipework

Quick Reference Table

Detailed Guidance

LPG Storage — Bulk Propane Tanks

Bulk propane tanks are the standard solution for LPG-heated homes. Tanks are typically filled by road tanker from the LPG supplier. Key aspects:

Tank ownership and supply: most tanks are supplied on a rental/lease basis by the LPG supplier. The supplier owns the tank and is responsible for its certification and integrity. The customer contracts for fuel supply. Changing supplier requires the tank to be decommissioned (or transferred if the new supplier accepts it), or a new tank installed.

Siting requirements (from LPGA Code of Practice 1 and HSE L56):

Notification: tanks over 75 litres must be notified to the local fire and rescue service (Fire Safety Order 2005, Dangerous Substances and Explosive Atmospheres Regulations 2002 — DSEAR). The LPG supplier typically handles this notification as part of tank installation.

Fire risk category: LPG is a highly flammable gas (Flammability Group IIA). Any installation involving LPG storage must be risk-assessed under DSEAR. For domestic installations, this is implicit in the LPGA CoP compliance.

Tank access for filling: the road tanker needs access to within approximately 30m of the tank (typical LPG fill hose length). Tanks placed in confined gardens without clear vehicle access cause practical supply problems.

Regulator Systems

LPG storage pressure is approximately 7 bar for propane at 20°C. This must be reduced to appliance working pressure (37 mbar for propane domestic). This is done in two stages:

Two-stage regulation (standard for all but smallest installations):

1. First-stage regulator: reduces from tank pressure to intermediate pressure (typically 0.75–1.0 bar); this regulator is integral to the tank or on the offtake valve
2. Second-stage regulator: reduces to appliance working pressure (37 mbar); fitted at the building entry or at the appliance

Single-stage regulation (for cylinder-only portable installations): a direct regulator from cylinder to appliance at 28–37 mbar. Not suitable for large heating systems.

Automatic changeover regulators: for twin-cylinder installations, an automatic changeover valve switches from the empty cylinder to the full standby cylinder without interrupting supply. Used where refilling frequency is a concern.

Key Installation Differences from Natural Gas

Pipe sizing: LPG has a much higher calorific value per m³ than NG, so less gas by volume is needed for the same kW output. Pipe sizes are typically smaller — a 30kW boiler on LPG needs approximately 1.1 m³/h propane vs 2.9 m³/h NG. A 15mm copper run up to 6–8m is often adequate for a domestic LPG boiler. Verify with IGEM/UP/11 tables (different from BS 6891).

Appliance settings: LPG appliances use different gas jets (smaller orifice), different burner settings, and different gas valve spring pressure. A natural gas appliance cannot be operated on LPG without conversion — this is not a field adjustment but a manufacturer-approved conversion kit with changed jets. Always confirm the appliance is either supplied LPG-rated or has been correctly converted.

Tightness testing: use the same principles as BS 6891 but note the different operating pressure (37 mbar); test at working pressure for a minimum of 2 minutes.

Ventilation: because LPG vapour is heavier than air, ventilation for LPG appliances must include low-level ventilation to allow gas to disperse if there is a leak. A 15mm × 15mm (225mm²) ventilator at low level (within 150mm of floor) is required in any room where LPG is used or stored. Do not install ventilation only at high level as with NG appliances.

Emergency Procedures

If you smell gas (LPG): LPG is supplied with an odorant (ethyl mercaptan — the same as NG, a sulphurous smell). If you smell gas:

1. Do not operate any electrical switches
2. Open windows and doors
3. Turn off the tank valve at the tank
4. Do not use the building until the source is found and repaired
5. Call the LPG supplier's emergency line; propane: typically embossed on the tank or in the customer's supply agreement
6. Call 999 if there is a fire or explosion risk

No gas emergency service: unlike NG (National Gas Emergency Service on 0800 111 999), there is no unified LPG emergency service. Each supplier has its own emergency contact.

Caravans and Portable LPG

Caravan and motorhome LPG installations are regulated separately — by EN 1949 (specification for the installation of LPG systems on leisure accommodation vehicles). These require specific Gas Safe registration categories (CCCN1 for caravan gas). Do not apply domestic installation standards to vehicle/caravan installations.

Frequently Asked Questions

Can I convert a natural gas boiler to LPG?

Only with a manufacturer-approved LPG conversion kit. Conversion involves replacing the gas injector jets (smaller orifice for LPG), adjusting the gas valve, and reconfiguring any air/gas ratio controls. Not all boilers can be converted — check with the manufacturer. An LPG-converted boiler must be recommissioned and the Benchmark checklist updated to show LPG operation.

How do I size a propane storage tank?

A 500-litre tank typically holds approximately 400 litres usable propane at 80% fill (tanks are not filled above 80–85% for thermal expansion allowance). A typical 3-bedroom rural house heating predominantly on LPG uses 2,000–3,000 litres per year. A 500-litre tank requires filling 5–7 times per year. A 1,000-litre tank halves the filling frequency.

Can an LPG tank be installed inside a garage or utility room?

No — bulk LPG tanks must be installed externally. Cylinders (not bulk tanks) can be stored in a properly ventilated external cage adjacent to the building. Cylinders must not be stored in basements or below-ground spaces because LPG vapour sinks and will accumulate in any low point.

What's the difference between LPG and Calor Gas?

"Calor Gas" is a brand name — Calor is one of the UK's major LPG suppliers. "LPG" is the generic term (Liquefied Petroleum Gas). The fuel is the same regardless of supplier — propane (red/orange cylinders/tanks for Calor) or butane (blue cylinders for Calor domestic, green commercial). Other suppliers include Flogas (grey cylinders), AvantiGas, and Countrywide.

Do I need separate Gas Safe registration for LPG?

Yes — LP1 ACS assessment is a separate requirement from CCN1 (NG core). An engineer holding only CCN1 is not legally registered to work on LPG systems. Many engineers hold both NG and LPG ACS assessments. Check the engineer's Gas Safe card for LP1 or LPG categories before allowing LPG work.

Regulations & Standards

• IGEM/UP/11 — specification for the design, installation, testing, and maintenance of low-pressure LPG domestic and commercial installations

• LPGA Code of Practice 1 — LP Gas Association; design, installation and maintenance of LPG systems

• Gas Safety (Installation and Use) Regulations 1998 — all gas work including LPG

• HSE L56 — storage of LPG at fixed installations; guidance on safety distances

• DSEAR 2002 — Dangerous Substances and Explosive Atmospheres Regulations; applies to LPG storage

• BS 8553 — the filling and maintenance of LPG cylinders (relevant to cylinder management)

• LP Gas Association (LPGA) — codes of practice, technical guidance, member directory

• HSE — LPG Safety

• Gas Safe Register — LPG

• Calor — Installer Technical Centre — LPG installation technical resources

• gas safe requirements — Gas Safe registration including LPG categories

• boiler installation — boiler installation checklist (applies to LPG with modifications)

• gas pipe sizing — pipe sizing methodology (LPG tables differ from NG)

• carbon monoxide — CO safety for LPG appliances