Materials used for LPG piping should be suitable for the range of temperatures and pressures that could occur in service. Acceptable materials include carbon steel, copper, brass, and polyethylene plastics. 

steel pipes are very common material used in LPG pipeline. They are rigid and strong and can withstand mechanical damage better than other materials. Carbon steel pipes used may either be black or galvanized and should be at least standard weight (Schedule 40). Extra strong pipe (Schedule 80) may be required depending on pipe size, working pressure and method of jointing. Jointing can be by thread, welding or flange connections. 

Cast iron fittings must not be used. 

Copper tubing is often used for domestic and small commercial installations. Although tubing costs much more than steel pipes of the same capacity, there is considerable saving of labour in its installation and maintenance. Since tubing may be bent readily, it is more easily installed and fewer fittings are required. However, it is more vulnerable to mechanical damage and it does not generally produce neat piping unless it is installed with particular care. Copper tubing can be affected by sulphur so it must be used with a LPG low in sulphur content. 

Polyethylene (PE) pipes are normally used for buried pipe sections. They are lightweight and corrosion-resistant. Jointing can be by means of compression fitting, factory assembled fitting or heat fusion. The latter is usually done automatically with a fusion machine which ensures a good joint. PE pipes and pipe fittings used should be PE80 or PE100 rating. 

Other materials used for LPG piping includes Corrugated Stainless Steel Tubing (CSST) and multilayer pipes. These materials are flexible and corrosion-resistant and jointing method is by use of proprietary fittings and tools. Additional information should be sought from manufacturer when such materials will be used. 

All piping and tubing must only be installed by approved installers. 

LPG appliances supplied with incorrect inlet pressure will result in inefficient burner performance or may not function at all. 

LPG piping is typically designed to have two-stage pressure regulation to minimise risks of the regulator freezing and condensation in the pipeline. First stage pressure reduces tank pressure to not more than 1.4 bar (20 psi-30- psi). The second stage further reduces the LPG pressure entering the building to not more than what the cooking appliance required which is typically 300mm water column WC (11 inch WC). 

Twin stage regulators are available that combines the first and second stage pressure regulation in one device and is usually used for sites with low consumption. 

Some LPG piping design may require three stages of pressure regulation i.e. if the appliance is located far from the second stage regulator. In this case, the second stage regulator will reduce it to an intermediate pressure of 340 mbar (5 psig) or the maximum allowed by local regulation whichever is lower. The third and final stage regulator reduces the pressure to the appliance requirement of 300mm (WC) – 11 inch WC. 

Pressure regulators are available with Over Pressure Shut Off (OPSO) and Under Pressure Shut Off (UPSO) devices. These devices shut off the flow of LPG downstream of the regulator when the pressure exceeds or falls below the set levels to prevent any incident from arising due to abnormal LPG line pressures. Some local regulations may require use of such devices on the LPG piping.

Flexible hoses if used should be of the correct pressure rating and material designed for LPG. This is usually reinforced rubber or plastic with metal braiding and marked with ‘LPG Hose’. There are no specific recommendations on the replacement intervals for hoses but 5 years is considered a normal useful life for rubber hoses which should not be exceeded. Note that adverse operating conditions could shorten the useful life of hoses. 

Metal flexible hoses made of corrugated stainless steel are also available for connecting appliances to the gas pipe. These hoses have a longer life span and in some countries are allowed to be used for 10 years before they are replaced. 

It is important to use qualified and approved flexible hoses.
There are flexible hoses in the market made of inferior material and using them may lead to accidents.