gas pipe sizing for boiler installation

[ant101]

I understand the theory behind sizing gas pipes and I have applied this to a real situation. Without going into it too deep I have calculated that i need to start with 28 mm pipe from the meter and then drop down to 22mm all the way to the boiler.I am only installing the pipework. The experienced gas engineer tells me I can go from 22 (from the meter) and then up to 28mm across the attic then back to 22mm. This just dosent make sense to me if the 28mm is proceded by 22mm.

If I was correct and you do start with 28mm will this still be as effective as the meter unions are only 22mm, therefore starting off with 22mm pipe anyway. Or can they be changed.

sorry if im not making sense.

student.
Thanks for any help

 

[clarkerothwell]

i saw a job by BG last week , normal u6 (212ft3) meter, ordinary 22mm union on meter, converted to 28mm straight away, then ran about 10m and then down to 22mm to boiler.

 

[Parkymike]

If your gas engineer is going to take on Your gas pipe then he is a brave man. Any problems i.e poorly soldered joints wrong fluxes that may corrode pipes and cause future leaks e.t.c will be his problem and in a court of law he would not be able to say 'he did that bit' your honour.
If I was you I would get someone who will insist on doing the work himself as it means he has more pride in his finished job and knowledge of a good job instead of always being worried.
I will not take on a half finished installation as you don't know what's been done.
In response to your question though you can buy a 28mm meter tail and any decent gas fitter would know that and recommend it's use.

 

[dd1975]

22x28mm reducer turned upside down to increase pipe onto meter tail , i would start personally in 28mm and reduce to 22mm

 

[kirkgas]

if it is a U6 meter buy a 1" x 28mm meter tail rather than start with a reduction

 

[gas4you]

A 22-28mm reducer upside down will pass more gas than the meter is capable of passing.

I have recently fitted the 28mm meter tails, but have found if the meter is on an approved bracket the extra diameter of the 28mm tail stops the meter unions fixing to the meter