Gas pipe sizing

[Agile]

If anyone ever has any feeling that they dont fully understand anything then its always better to ask to clarify rather than continuing to be unsure.

Over pipe sizing people can get into serious trouble if they fit a boiler on an undersized pipe. CORGI can issue a defects notice and that requires the RGI to correct it at HIS own cost. That can be expensive if its 20 m of 28 mm tube.

As Chris has pointed out actual pressure drops are often about 20% more than calculated figures because of the roughness of joints etc.

Tony

 

[chrishutt]

I plan to come from the meter in 28mm and then tee the existing 22mm supply to the BBU straight after it leaves the meter and carry on all the way with the new pipe to the new boiler in the extension approx. 20 metres away. My question is,for getting the correct pipe size,do I just calculate the length of the new supply or do I need to add the other appliances into the mix,seeing as they will tee off within 150mm of the meter outlet-

Simple question with a simple answer. The first 150mm (or less) of 22mm pipe will carry the full load of all appliances. However since the length is so short the pressure drop is very small, depending mainly on the number of elbows. With say 2 x 22mm elbows and the tee, the equivalent length would be about 1.5 metre (of 22mm) which would give a pressure drop of around 0.2 mbar, even assuming the overall load was 50 kW. That would leave you with 0.8 mbar to play with for the new run.

Taking your new boiler run of 20 metres + say 4 metres allowance for say 8 bends and with a load of say 31 kW or approx 3.0 cubic metres /hr, a 24 metre run of 22mm pipe would give a pressure drop of about 1.2 mbar, so you would only need about half the run to be 28mm (giving a third of the pressure loss compared to 22mm) to end up with an overall drop of about 1.0 mbar, including the 0.2 mbar drop near the meter.

Bear in mind that I've made a lot of assumptions above, and it's based on the values given in the tables which may be unrealistically low, as ChrisR pointed out. You'd certainly be all right if almost all of the new run was 28mm.

 

[chr15]

Yes,my plan would have been to run most of the new pipe in 28mm with the last few metres in 22mm if possible once i've done all the calcs.
If the others had come up with a similar answer to this instead of trying to belittle posters with arrogance then life would be a lot simpler. Thanks for the reply.

 

[kevplumb]

once i've done all the calcs.

so why didn't you do the calcs

if your an RGI i ain't got a ole in my arse

 

[chr15]

once i've done all the calcs.

so why didn't you do the calcs

if your an RGI i ain't got a ole in my a**e

So why didnt YOU answer the question in the first place with all your arrogance-as to whether you got a hole in your a**e,I don't wanna know about it,maybe post that stuff on another type of board sweetie.

 

[kevplumb]

So why didnt YOU answer the question in the first place with all your arrogance-as to whether you got a hole in your a**e,I don't wanna know about it,maybe post that stuff on another type of board sweetie.

cos i ain't about to help some slipshod cowboy steal the bread from an RGI

that is why

there may be some PRATTS that post on here that will give you the answers

one of them aint me bonny lad

 

[chr15]

So why didnt YOU answer the question in the first place with all your arrogance-as to whether you got a hole in your a**e,I don't wanna know about it,maybe post that stuff on another type of board sweetie.

cos i ain't about to help some slipshod cowboy steal the bread from an RGI

that is why

OK, thats got nowt to do with it-you just trawl the posts waiting for someone you can jump on,funny how you didnt come up with a technical answer at the beginning and then got arsey as soon as somebody else did-and if you're so clever,why would you be worried about someone stealing bread from an RGI,not a problem for you with your vast knowledge.

 

[kevplumb]

again i will say you are NOT an RGI

or you would not be asking advice on a DIY forum

smart ass e mail me your card number

 

[chr15]

You are the smart ass,why should I e-mail you anything, I seen plenty of RGI'S ask questions on this site,is that a hard and fast rule or just one you decided to make up so you can keep having a go?

 

[kevplumb]

You are the smart ass,why should I e-mail you anything, I seen plenty of RGI'S ask questions on this site,is that a hard and fast rule or just one you decided to make up so you can keep having a go?

so don't fella no skin off me

ive got my number

 

[chr15]

Well you know what,in different circumstances I would gladly send you my no. but I just dont trust you,attitude an all that,and the replies I see you give to other posters,courtesy costs nothing, so go on,carry on feeding your ego. And by the way,what makes you think that carrying the little card makes you safe-in general like,cos I have come across a few installs and services by so-called RGI'S which would make your eyes water so I don't see why your banging on about the corgi card being the be all and end all cos it's not.

 

[kevplumb]

BLOODY ARGI membership is tho

so why not join

 

[chr15]

b****y ARGI membership is tho

so why not join

Well Mr know everything....how do you know I'm not a member? I tell you one thing-there replies have usually got a lot less sarcasm attatched to them than yours-now who's the smart ass-I am a member.

 

[kevplumb]

e mail me your username smartass

I AM THE MEMBERSHIP SEC

 

[chr15]

e mail me your username smartass

I AM THE MEMBERSHIP SEC

Thought so,I wonder why I don't want to do that either,looks like thats another site I won't be using in the future.