sneaky said:I only wanted to know the size of pipe so i can notch the joists in preparation before i get the plumber in. I will then be more than happy to pay a plumber £20 an hour for the skilled task of connecting the gas supply.
Surely we have explained to you the gas pipe size has to be calculated. If you cannot do that then you must ask the RGI to do it for you.
As he will be taking responsibility for its performance then he should want to. If the pressure loss is more than 1 mB then you can complain to CORGI and they will serve a defects notice requiring him to correct it at his expense. So its in his own interest to do it correctly!
Even if its calculated properly the practical loss is always higher than that calculated, I would say 20% but Chris says 70%.
Tony