15mm gas supply to new 30kW system boiler - OK?

[Rory]

Typical U6 Meter on low pressure domestic service would be expected to be 21 mbar outlet working +/- 2 mbar.
They can be different, this is what is typical/expected.
You would expect (by design) a drop of 1 mbar meter to appliance working. This too can be different dependent on a number of factors but still be deemed acceptable. You'll have to trust me on that. Not got time to go through the technicalities.

You obviously have concerns. In my opinion you need a second opinion or to make it official, you would need to contact Gas Safe. If they do come to inspect the work, they will want the installer on site during the visit so you might want to discuss this with him and explain why you are considering it. Just to give him chance to go through it with you in enough detail to put your mind at ease.

Thanks for that, appreciate it.

I think I'm just going to live with it. It's become apparent that replacing the gas pipe would not be the drama I thought it would as I insisted that I wasn't happy with the top edge of the cylinder pressing into the gas pipe - the fitters solution was to drain the cylinder, undo its connections and move it slightly.

I know it's true that the boiler will rarely run flat out - I just can't get my head around the gas carrying capacity of that length of 15mm tube seems miles below the boiler's max demand.