What type of gas pipe in undergorund conducting - in new build

Trac Pipe Is Suggested. The size (CSA) required is dependent on the Volume of gas it will need to carry under full demand, and it should also allow for expansion of volume in the future (I.e. adding additional or larger demand appliances). I.e. the maximum demand on a domestic property is appx 6m3 per hour on a domestic G4/U6 mater, and 16m3/Hr on a U16. The appliances will all draw a certain Maximum volume of gas to operate safely and within the manufacturer's instructions to ensure no pressure loss when all appliances are running at full rate. The meter regulator will also need testing when finally connected to appliances. Any errors here and the property and persons are AT RISK. In the event of an incident your Buildings and Contents insurance, life insurance etc are in breach of the small writing and possible criminal proceedings can follow. The British Standards have published in 2015, which cost appx £300, have the latest pipe sizing requirements because if you undersize gas pipework the installed and connected gas appliances will not get sufficient gas at the required operating pressure and this can lead to Carbon Monoxide. Tracpipe is only for underground use, copper or steel once it rises from the ground. The pipework must be tested for gas tightness using a manometer once laid and again after the infill and slabs returned/fitted and then tested again after. The British Standards latest publication in 2015 gives ruling for the bury depth under pathways for pedestrian or public traffic. This must all be pre-planned before buying or laying.You can lay your own pipework, but YOU MUST NOT CONNECT IT TO ANY GAS SUPPLY. EXISTING OR NEW. THIS WOULD BE ILLEGAL A suitable competent and Gas Safe Registered Engineer MUST DO THIS!!! Pipe sizing is a complicated set of maths and has many many variable. You cannot simply make a guess at at the size or someone's advise unless all the data is provided, i.e. heat input in KW of the appliance, appliances it will feed. Certainly you can plan (With Help) Dig up your path, and lay end to end and plug the ends, but then you will need a registered gas engineer to test it and make the connections to the gas supply, existing pipework, and appliances. Beyond that you could face prosecution or hefty fine from the HSE. If you are at the planning stage by all means you can get advise from a professional gas consultant, or professional, (NEEDED), make the space, do the digging etc to keep costs down . BUT again you will need a registered competent gas safe licenced engineer throughout the planning and then connection, testing and certifying. Every bend in the pipe will lower the pressure and Hope this helps.

You should use a Gas Safe engineer to install Trac pipe for you.

It depends on wot kw appliances you are running

I would use track pipe and reference the sizes it has to worked out for your gas appliances that will be using the gas supply ,as a gas safe engineer can call to site and work out the kw required and then he or she can confirm the size of pipe requirements.