Gas Supply Pipe Size

[Paulhar]

Hi All,
I'm about to upgrade a regular boiler for a customer and if I use 22mm copper all the way then I'll be right on the limit for pressure loss. The boiler takes 2.6 cu mtrs and the effective length of the pipe will be 24 metres. My question is, can I go up to 28mm for 3 metres in the middle of the run, ie 22 from the meter, then up to 28 and then back down to 22 - or does the largest diameter pipe have to be from the meter ?

Cheers
Paul

 

[allanmcm]

28 from start of meter

 

[diamondgas]

From the meter, reducing further downstream Paul...

 

[kirkgas]

it will work best if the largest pipe is at the meter end, but will work well enough with the large pipe in the middle, gas compresses and expands to the size of the pipe it is in, unlike water which must have the large pipe at the start of the run.
there will be many installs that we check that are done like this under a floor, up the loft or inside boxing in that we cant inspect but when we do pressure tests the result is fine

 

[Ian10261]

it will work best if the largest pipe is at the meter end, but will work well enough with the large pipe in the middle, gas compresses and expands to the size of the pipe it is in, unlike water which must have the large pipe at the start of the run.
there will be many installs that we check that are done like this under a floor, up the loft or inside boxing in that we cant inspect but when we do pressure tests the result is fine

Thats well useful to know, would only go down that route if absolutely necessary though ie: if it means demolishing part of the house instead.

 

[AWheating]

like kirkgas said, gas pressure/flow loss is different than water so dont think along the same terms. Ive known many engineers who dont think its worth putting 28mm pipework in due to the fact the exsisting meter tail is 3/4 and its restriction will make the 28mm pointless.

GOOD LUCK

 

[mikeygas]

Don't forget about any other appliances on the gas carcuss?

Have used 28mm pipe in middle of pipe runs or even at the boiler end of the pipe run before reducing down to 22mm, when access difficult or laminate/vinyl floor. Dosn't matter where it goes as like Kirrky says gas once compressed don't stay compressed it will expand and compress to fill whatever diameter of pipe it passes through.

 

[allanmcm]

i thought it was in the gas regs u cldnt go down then up again. stand to be corrected though .not good practice anyway. have seen sections of 15 mm in a gas run make a big difference

 

[Gray0689]

i thought it was in the gas regs u cldnt go down then up again. stand to be corrected though .not good practice anyway. have seen sections of 15 mm in a gas run make a big difference

You can do what you want with pipework as long ad the required amount of gas gets to the appliances

 

[Blackcatgas]

You can also run 2 pipes, say 2 x 22mm if you needed to and conect them at both ends.

 

[Paulhar]

Hi Guys,
Thanks for all the replies. It will make life a lot easier for me if I can just insert a 28mm section in the middle - no redrilling, re-sleeving etc. 22mm all the way may be ok but I'd like to be on the safe side.

 

[stevetheplumber]

we had this question a while back and i was shot down in flames when i suggested it was ok to upsize at any point in the run which is what i was told many years ago on my first acop course
when i checked with gas safe tech they said it was a no no however when i asked how to connect 35mm copper to a domestic meter they said start in 22 the increase to 35 i then questioned this in view of the previous reply and they then said it was allowed
i can see no problem with it as all you are doing is reducing the wall friction

 

[kirkgas]

Thats well useful to know, would only go down that route if absolutely necessary though ie: if it means demolishing part of the house instead.

it isnt my first option,, but knowing it will work has stopped me ripping up a bit of tiled or laminate flooring in the past, as long as it checks out when done then jobs a good un

 

[kirkgas]

i thought it was in the gas regs u cldnt go down then up again. stand to be corrected though .not good practice anyway. have seen sections of 15 mm in a gas run make a big difference

haha stand up then, we arent talking about reducing a section of pipe, but increasing it, which will have the opposite effect

 

[tamz]

Gas does not behave like water, think about it.

 

[bengasman]

You will get the most improvement from 28 mm if you do it at a point where there are a lot of elbows.
Is there a practical reason why you only would do 3 metres?

 

[mylesy]

id stick to large moving down, you can compress gas but its flow is restricted in narrower pipes, frictional resistance is less in larger pipes. plus pressure reduces the further away from the inlet source.

 

[mylesy]

you can get a venturi effect by bottle necking at narrow pipeways in the center of a system.