Question 1

What size LPG pipe do I need for a house in Australia?

Accepted Answer

For a standard residential LPG installation with a cooktop and hot water system (total load around 190 MJ/h), you'll typically need a DN32 or DN40 copper main line from the regulator, depending on the pipe run length. Short runs under 10 metres might squeeze into DN32, but longer runs generally need DN40. Always check the AS/NZS 5601.1 LPG capacity tables for your specific load and distance.

Question 2

What is the difference between LPG and natural gas pipe sizing?

Accepted Answer

LPG is 2.5 times heavier than natural gas (specific gravity 1.52 vs 0.60) and packs 2.4 times more energy per cubic metre (93.3 MJ/m³ vs 38.7 MJ/m³). LPG also runs at a higher supply pressure (2.75 kPa vs 1.05 kPa). Because of these differences, the pipe capacity lookup tables are completely different. You cannot use natural gas tables for LPG sizing.

Question 3

How many 45kg gas bottles do I need for a house?

Accepted Answer

Most homes with a cooktop and either a gas heater or gas hot water system need a dual 45kg manifold at minimum. A single 45kg bottle only supplies about 65 MJ/h continuously — not enough if your total load exceeds that. Dual bottles give you about 130 MJ/h and provide automatic changeover so you never run out mid-shower.

Question 4

What is a stage 2 regulator on LPG?

Accepted Answer

A stage 2 regulator is the second pressure reduction device in an LPG system. The first-stage regulator on the cylinder drops the high bottle pressure (800-1200 kPa) down to about 35 kPa. The second-stage regulator on the house wall drops it further to 2.75 kPa for delivery to household appliances. Most residential LPG installations in Australia use this two-stage setup.

Question 5

What pressure does LPG run at in a house?

Accepted Answer

Standard residential LPG pressure is 2.75 kPa at the second-stage regulator outlet. Appliances need at least 2.25 kPa at their inlet to operate properly. That leaves a 0.50 kPa pressure drop budget for the internal pipe run from the regulator to the furthest appliance.

Question 6

Can I use the same gas pipe for LPG and natural gas?

Accepted Answer

The physical pipe materials (copper, steel, PEX-AL-PEX) are the same for both gases. However, you cannot simply swap from one gas to the other without resizing — the pipe capacity tables, regulator pressures, and appliance orifices are all different. Converting from NG to LPG (or vice versa) requires a licensed gasfitter to recalculate pipe sizes, change regulators, and re-jet every appliance.

Question 7

Why does my LPG gas bottle frost up?

Accepted Answer

Frosting happens when you draw gas out of the cylinder faster than the liquid LPG can boil off. The rapid evaporation absorbs heat from the bottle wall, causing moisture in the air to freeze on the outside. It means the bottle is being asked to deliver more gas than it can handle. The fix is to add more cylinders (manifold) or upgrade to a bulk tank.

Question 8

What is the maximum gas load a single 45kg LPG bottle can supply?

Accepted Answer

A single 45kg LPG cylinder can continuously supply about 65 MJ/h in mild weather (20°C+). In cold conditions below 5°C, this drops to about 40-50 MJ/h because the liquid propane boils off more slowly. If your total appliance load exceeds the bottle's withdrawal rate, the gas pressure drops and appliances start cutting out.

Question 9

Do I need a licence to install LPG gas pipes in Australia?

Accepted Answer

Yes. All LPG gas fitting work must be carried out by a licensed gasfitter in every Australian state and territory. This includes running new pipe, connecting cylinders, fitting regulators, and commissioning appliances. A gas compliance certificate must be lodged after every installation.

Question 10

Can I use PEX-AL-PEX for LPG piping?

Accepted Answer

Yes, PEX-AL-PEX (multilayer pipe with aluminium core) is approved for LPG installations under AS/NZS 5601.1. Make sure you use gas-rated press or push-fit fittings designed for that specific pipe brand. Note that PEX-AL-PEX has smaller internal diameters than copper, so you'll often need to go up a size to carry the same MJ/h load.

Question 11

How far can LPG bottles be from the house in Australia?

Accepted Answer

AS/NZS 5601.1 sets minimum clearance distances for LPG cylinders. For cylinders up to 55kg aggregate, the minimum distance from an opening (window, door, vent) is 1 metre, and from an ignition source is 3 metres. For larger installations, the distances increase. Your state gas authority may have additional local requirements.

Question 12

What is medium pressure LPG and when do I use it?

Accepted Answer

Medium pressure LPG runs at around 7 kPa — higher than the standard 2.75 kPa residential low pressure. It's used on rural properties with long pipe runs (30 metres or more) where the 0.50 kPa pressure budget at 2.75 kPa isn't enough. With 7 kPa supply, you get a 4.25 kPa drop budget, allowing smaller pipes over longer distances. Each appliance gets its own individual regulator to drop from 7 kPa to 2.75 kPa.

Question 13

How do I convert MJ/h to kg/h for LPG?

Accepted Answer

LPG (propane) has a gross calorific value of about 50.2 MJ per kilogram. To convert from MJ/h to kg/h, divide the MJ/h rating by 50.2. For example, a 157 MJ/h instantaneous hot water system uses about 3.1 kg/h of LPG. This is useful when checking cylinder discharge rate limits.

Question 14

Can I install a bulk LPG tank myself?

Accepted Answer

No. Bulk LPG tank installations (190kg and above) must be carried out by a licensed gasfitter and approved by your LPG supplier (Elgas, Origin, Kleenheat, Supagas, etc.). The tank remains the property of the supplier in most cases. The supplier handles installation, testing, and compliance. You are responsible for the piping from the tank to the house.

Question 15

What happens if my LPG pipe is too small?

Accepted Answer

An undersized LPG pipe causes a pressure drop greater than 0.50 kPa at the appliance inlet. The symptoms are the same as undersized natural gas piping: appliances cut out on error codes, yellow or lazy flames on cooktops, hot water systems failing to ignite, and gas heaters running below rated output. A manometer test at the appliance inlet will confirm low pressure.

Cylinder Setup	Max Continuous Withdrawal	Best Suited For
Single 45kg Bottle	~65 MJ/h	Cooktop only / BBQ bayonet
Dual 45kg Manifold (Changeover)	~130 MJ/h	Standard house (Cooktop + HWS)
4× 45kg Manifold Bank	~260 MJ/h	Large home / Multi-appliance
Bulk Tank 190kg	~200 MJ/h	Permanent rural residential
Bulk Tank 500kg+	~450 MJ/h	Commercial kitchens / Farms

Pipe Size	5m Run	10m Run	15m Run	20m Run	25m Run	30m Run
DN15 (15mm)	37 MJ/h	26 MJ/h	21 MJ/h	18 MJ/h	16 MJ/h	15 MJ/h
DN20 (20mm)	86 MJ/h	61 MJ/h	50 MJ/h	43 MJ/h	38 MJ/h	35 MJ/h
DN25 (25mm)	161 MJ/h	114 MJ/h	93 MJ/h	81 MJ/h	72 MJ/h	66 MJ/h
DN32 (32mm)	298 MJ/h	211 MJ/h	172 MJ/h	149 MJ/h	133 MJ/h	122 MJ/h
DN40 (40mm)	469 MJ/h	332 MJ/h	271 MJ/h	235 MJ/h	210 MJ/h	191 MJ/h
DN50 (50mm)	960 MJ/h	679 MJ/h	554 MJ/h	480 MJ/h	429 MJ/h	392 MJ/h

LPG Gas Pipe Sizing Calculator Australia

1. Select Your LPG Gas Appliances

2. LPG Setup & Pipe Config

Natural Gas Pipe Sizing Calculator

Hot Water System Sizing Calculator

How LPG Pipe Sizing Differs From Natural Gas

The LPG Pressure System in Australia

LPG Cylinder Types and Vapour Withdrawal Limits

LPG Pipe Capacity Quick Reference — Copper (AS/NZS 5601.1)

Real-World Worked Example: Off-Grid QLD Farmhouse

Common LPG Pipe Sizing Mistakes on Australian Sites

Frequently Asked Questions