Hi all,
I have a slightly odd question about D2 discharge pipes from an unvented cylinder.
Approved document G in table 3.1 gives all the pipe sizing for different lengths.
But then has these other statements which slightly contradict each other.
3.58 The discharge pipe D2 should be at least
one pipe size larger than the nominal outlet size
of the safety device unless its total equivalent
hydraulic resistance exceeds that of a straight
pipe 9m long, i.e. for discharge pipes between
9m and 18m the equivalent resistance length
should be at least two sizes larger than the
nominal outlet size of the safety device; between
18 and 27m at least 3 sizes larger, and so on;
bends must be taken into account in calculating
the flow resistance. See Diagram 1, Table 3.1 and
the worked example.
3.59 Where a single common discharge pipe
serves more than one system, it should be
at least one pipe size larger than the largest
individual discharge pipe (D2) to be connected.
3.59 makes it seem like you can step up the pipe size, from say a 22mm to 28mm when you hit your 9m limit by calling it a common discharge pipe. This would potentially save you in using expensive 28mm copper on the whole run of D2.
or perhaps..
If you were in a block of 4 flats and you didn't want to discharge into the soil stack over concerns about temperature ratings. You could effectively run 22mm pipe to a
"Single common discharge pipe" of 28mm which exited appropriately at ground level.
Both of these things would seem to comply with 3.59 but might somewhat contradict 3.58 which tells you how to upsize your pipe if its straight run is over 9m or 18m.
https://assets.publishing.service.g...207/BR_PDF_AD_G_2015_with_2016_amendments.pdf
Really interested in your thought on this.
This might just be some really clumsily written documentation
Cheers
A
I have a slightly odd question about D2 discharge pipes from an unvented cylinder.
Approved document G in table 3.1 gives all the pipe sizing for different lengths.
But then has these other statements which slightly contradict each other.
3.58 The discharge pipe D2 should be at least
one pipe size larger than the nominal outlet size
of the safety device unless its total equivalent
hydraulic resistance exceeds that of a straight
pipe 9m long, i.e. for discharge pipes between
9m and 18m the equivalent resistance length
should be at least two sizes larger than the
nominal outlet size of the safety device; between
18 and 27m at least 3 sizes larger, and so on;
bends must be taken into account in calculating
the flow resistance. See Diagram 1, Table 3.1 and
the worked example.
3.59 Where a single common discharge pipe
serves more than one system, it should be
at least one pipe size larger than the largest
individual discharge pipe (D2) to be connected.
3.59 makes it seem like you can step up the pipe size, from say a 22mm to 28mm when you hit your 9m limit by calling it a common discharge pipe. This would potentially save you in using expensive 28mm copper on the whole run of D2.
or perhaps..
If you were in a block of 4 flats and you didn't want to discharge into the soil stack over concerns about temperature ratings. You could effectively run 22mm pipe to a
"Single common discharge pipe" of 28mm which exited appropriately at ground level.
Both of these things would seem to comply with 3.59 but might somewhat contradict 3.58 which tells you how to upsize your pipe if its straight run is over 9m or 18m.
https://assets.publishing.service.g...207/BR_PDF_AD_G_2015_with_2016_amendments.pdf
Really interested in your thought on this.
This might just be some really clumsily written documentation
Cheers
A
