Is this the proper forum to ask a question about the proper size of gas lines? It's not a DIY question, I'm just confused about the existing system in my house and want to see if I'm not understanding things correctly before I call somebody in to look. Since gas lines generally fall under plumbing, I thought this might be the place to resolve my confusion.
Gas line sizing question
- Thread starter Yidney
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I am a b class gasfitter and will attempt to answer any questions you may have, note that codes may vary depending on location as I am In Canada and my work falls under the Canadian gas code. there are other gasfitters present here as well.
Thanks. Recently I was looking at the method for calculating gas pipe sizes that seems to be pretty universal in the US - where you measure the distance to the farthest appliance, calculate the BTUs' on each branch, then refer to a table for sizing. I'm sure you now what I'm talking about. So I got curious about my own house. It's 50' to the water heater. Two questions:
1. If I look at the table, in a house with a 50' run, the most a 1/2" pipe can carry is 73 cf/m (73,000 BTU). But yet my 90,000 BTU furnace is connected with 1/2" line and the furnace is designed to take a 1/2" line. I'm guessing furnaces are routinely connected that way, and mine was permitted and inspected. So what am I missing? Why can furnaces be connected in a way that appears to be a per se code violation?
2. My main line is 1". That's plenty for the few gas things I have. But at the end of the 1" pipe it is reduced to 1/2", then there is a 12" run of 1/2" to a "T" where one line goes to the water heater (38,000 BTU) and one to the furnace. That short 12" section of 1/2" shared pipe has to carry 128 cf/m if both are running. That's just wrong isn't it? That short section should be at least 3/4" shouldn't it?
1. If I look at the table, in a house with a 50' run, the most a 1/2" pipe can carry is 73 cf/m (73,000 BTU). But yet my 90,000 BTU furnace is connected with 1/2" line and the furnace is designed to take a 1/2" line. I'm guessing furnaces are routinely connected that way, and mine was permitted and inspected. So what am I missing? Why can furnaces be connected in a way that appears to be a per se code violation?
2. My main line is 1". That's plenty for the few gas things I have. But at the end of the 1" pipe it is reduced to 1/2", then there is a 12" run of 1/2" to a "T" where one line goes to the water heater (38,000 BTU) and one to the furnace. That short 12" section of 1/2" shared pipe has to carry 128 cf/m if both are running. That's just wrong isn't it? That short section should be at least 3/4" shouldn't it?
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There is a total length of 12" of 1/2" before the 1/2" T, then after the T there is about 12' to the water heater and 6' to the furnace.
But I'm as interested in understanding the answer as I am in getting the correct answer. When you say "plenty left over" at the end of the 1/2" pipe, how does that relate to the chart that says a 1/2" pipe should only carry 73cf/m in a system with a 50' run?
But I'm as interested in understanding the answer as I am in getting the correct answer. When you say "plenty left over" at the end of the 1/2" pipe, how does that relate to the chart that says a 1/2" pipe should only carry 73cf/m in a system with a 50' run?
1. If I look at the table, in a house with a 50' run, the most a 1/2" pipe can carry is 73 cf/m (73,000 BTU). But yet my 90,000 BTU furnace is connected with 1/2" line and the furnace is designed to take a 1/2" line. I'm guessing furnaces are routinely connected that way, and mine was permitted and inspected. So what am I missing? Why can furnaces be connected in a way that appears to be a per se code violation?
My canadian code book ( Csa-b139.1.05 ) under table a.2 Maxmum capacity of natural gas in thousands of btu for Sched 40 pipe based on systems for pressures of 7-14 inches W.c shows
50 foot run, 1/2 " will carry 95,000 btu
3/4" - 199,000 btu
where as on table A.1 ( the same table except > pressures less than 7" wc.
50 foot run, 1/2" - 65 000 btu
Are you sure youre on the right table?
2. My main line is 1". That's plenty for the few gas things I have. But at the end of the 1" pipe it is reduced to 1/2", then there is a 12" run of 1/2" to a "T" where one line goes to the water heater (38,000 BTU) and one to the furnace. That short 12" section of 1/2" shared pipe has to carry 128 cf/m if both are running. That's just wrong isn't it? That short section should be at least 3/4" shouldn't it?
Yes, it should feed 3/4 and then a 3/4 X 1/2 X 1/2 T to feed the appliances, you will be getting improper combustion if they are both running possiblly sooting and improper venting.
On the Furnace note, as mentioned above with 7-14 " w.c. a 1/2" line can carry 95,000 btu so the 1/2" does this job fine. This also is why many boilers are 3/4 ( most I see anyways ) as they must run more btus to provide enough to overcome heat losses in a heating system and, lets face it... If you have a boiler, then why not run an indirect HWT also.
My canadian code book ( Csa-b139.1.05 ) under table a.2 Maxmum capacity of natural gas in thousands of btu for Sched 40 pipe based on systems for pressures of 7-14 inches W.c shows
50 foot run, 1/2 " will carry 95,000 btu
3/4" - 199,000 btu
where as on table A.1 ( the same table except > pressures less than 7" wc.
50 foot run, 1/2" - 65 000 btu
Are you sure youre on the right table?
2. My main line is 1". That's plenty for the few gas things I have. But at the end of the 1" pipe it is reduced to 1/2", then there is a 12" run of 1/2" to a "T" where one line goes to the water heater (38,000 BTU) and one to the furnace. That short 12" section of 1/2" shared pipe has to carry 128 cf/m if both are running. That's just wrong isn't it? That short section should be at least 3/4" shouldn't it?
Yes, it should feed 3/4 and then a 3/4 X 1/2 X 1/2 T to feed the appliances, you will be getting improper combustion if they are both running possiblly sooting and improper venting.
On the Furnace note, as mentioned above with 7-14 " w.c. a 1/2" line can carry 95,000 btu so the 1/2" does this job fine. This also is why many boilers are 3/4 ( most I see anyways ) as they must run more btus to provide enough to overcome heat losses in a heating system and, lets face it... If you have a boiler, then why not run an indirect HWT also.
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I've googled "gas line sizing" and similar things, and come up with a single table from numerous jurdictions around the US, and it always looks like a single table for residences, and always the same numbers - give or take a cf/m or two.
Thanks for the answer on the 1/2" section needing to be 3/4", but I'm still stumped about the furnace if I'm reading these tables right.
Here is the first one I looked at that got me curious.
http://www.ci.pleasanton.ca.us/pdf/bldg-gaspipe.pdf
Could you put a 90,000 BTU furnace on a 1/2" line in Pleasanton, CA in a house with a 50' run?
Thanks for the answer on the 1/2" section needing to be 3/4", but I'm still stumped about the furnace if I'm reading these tables right.
Here is the first one I looked at that got me curious.
http://www.ci.pleasanton.ca.us/pdf/bldg-gaspipe.pdf
Could you put a 90,000 BTU furnace on a 1/2" line in Pleasanton, CA in a house with a 50' run?
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the table in the link says allowable pressure drop of 0.5 " wc. which means it is a table for a supply pressure of less than 7" wc. which is not typical, usually your natural gas supply will be between 7-14" wc. which allows for a pressure drop of 1" wc., So I believe you are using the wrong table.
Could you put a 90,000 BTU furnace on a 1/2" line in Pleasanton, CA in a house with a 50' run?
Not according to that particualr table, but there are likely other tables that would allow for it, As I;ve said in my canadian gas codebook I can do it on a 7-14" wc. supply pressure but not a 0-7" wc. supply.
The only way to know for sure would be to check an actual codebook as this information could be different depending on location ( altitudes affect actual Btu consumption of an appliance, and in some cases appliances are de-rated due to their area of installation's altitude. ) Also this could be an outdated table.
Could you put a 90,000 BTU furnace on a 1/2" line in Pleasanton, CA in a house with a 50' run?
Not according to that particualr table, but there are likely other tables that would allow for it, As I;ve said in my canadian gas codebook I can do it on a 7-14" wc. supply pressure but not a 0-7" wc. supply.
The only way to know for sure would be to check an actual codebook as this information could be different depending on location ( altitudes affect actual Btu consumption of an appliance, and in some cases appliances are de-rated due to their area of installation's altitude. ) Also this could be an outdated table.
"Hello Yidney",
I have noticed something that SEEMS to be missing from the Table / Calculations / the Answers that You have seen - although Please accept My Apology if I have somehow missed this:
When calculating the Gas Pipe Sizes for within a Building / Home the `EQUIVALENT LENGTH` Method MUST be used - This may be known under a different `Name` in the U.S. - ?
This Method means that as well as the Measured Length of the actual Pipework the `Frictional Loss / Resistance` within the Pipework and Fittings MUST be calculated and Allowed For when using the Pipework Supply Tables.
To be able to do this You MUST know the Number of 90 Degree Bends - Tees etc. that are installed on EACH Section of the Gas Supply Pipework within the Building - and the `Frictional Loss` AMOUNT that has to be Allowed for.
For example here in the U.K. the Tables show the Amount of Natural Gas that can be Supplied from a STRAIGHT LENGTH of Gas Pipe - this is now shown / calculated in Cubic Metres per Hour and Metres of Pipe.
The Gas Pipework Internal System Pressure is [approximately] 21 Millibar [approx. 8"] Water Gauge with an `Allowable` Pressure Drop of ONLY 1 MILLIBAR Water Gauge across the Pipework System.
These figures are obviously significantly different to the 7" to 14" Pressures and the 1" permitted Pressure Drop that LiQuid stated is the `Norm` in Canada [and the U.S. ?].
When Calculating the Gas Supply Pipework it is necessary to Work Out the ACTUAL Length of the Pipework AND Also the `EQUIVALENT LENGTH` - which is the Actual Measured Length PLUS an `Added Length` for the Frictional Loss from the Fittings.
An example of the Allowance / ADDITION for each Fitting here in the U.K. is that each 90 Degree Elbow / Bend and Tee is ADDED as 0.5 Metres [0.3 Metres for a Sweep Bend] TO the actual Measured Length of the Pipework.
These figures are for Small Bore Domestic Gas Pipework.
So - A simple example would be:
If a Pipe that was Supplying only one Gas Appliance actually Measured 12 Metres and had 6 X 90 Degree Elbows / Bends - the `Equivalent Length` would be 15 Metres - having ADDED 3 Metres [6 X 0.5M] to the Measured Length.
The Method is a bit too complicated for Me to write an explanation here / Now - But basically You MUST Know the Total Gas Requirement for ALL of the Gas Appliances - This will govern the Size of the `Incoming Supply` and here in the U.K. the Model of the Meter.
Knowing what the Incoming Supply Pipe will Supply You must calculate EACH Section of the Internal Supply Pipework by actually Measuring the Length of the Pipework then counting the amount of Fittings - 90 Degree Elbows / Bends and Tees and ADDING whatever You find out to be the `Recommended` Frictional Loss / Resistance Factor in the U.S. - I do not know what this is likely to be in relation to these Tables showing the Supply Volume in BTU`s.
EACH Section would be the Actual Measured Length PLUS the Frictional Loss / Resistance Allowance for the Fittings = the `Equivalent Length` - THIS would then be used to Select / Check the Pipe Size from the CORRECT Gas Supply Table.
This Allowance for the `Extra` Metres / Feet of Pipework to allow for the Frictional Loss / Resistance is VITAL in Calculating the Pipework Sizes Correctly / Using the Gas Supply Tables Correctly.
The Total Amount of Fittings within a Home`s Gas Supply Pipework can cause BIG Differences in what these Gas Tables state a certain Length of Pipe will convey to an Appliance and what is actually Available at the Appliance - as the Tables are quoting the Amount of Gas / BTU`s supplied by a STRAIGHT Length of Pipe.
THIS cannot have `Been Allowed For` within the Tables as it would be an `Unknown Quantity` - I also have NOT seen any reference to this in the Answers that You have received.
Although I am a Gas Engineer [U.K.] - amongst other Qualifications unfortunately I cannot be of Help to You about the actual Calculation for your Home / Gas Supply Pipework to your Appliances at present because I am going to be away from Home on Business.
I will not be wanting to do any Calculations in the Evening when I am away - especially those which would require a `Correct` Gas Supply Table from the U.S. and a `Fittings Allowance` reference - and where the `Equivalent Length` Method does NOT seem to be used [?].
Good Luck in resolving Your Questions - while this `Explanation` / Method may not actually help with your Question - knowing more about this Method would help You to actually Calculate the Amount of Gas VOLUME / BTU`s that would be available at the point where the Pipework reduces in size / Where perhaps it should not have reduced to less than 3/4" Pipe - and the BTU`s / Volume that would be available at EACH Tee point and Appliance Inlet - regarding other Appliances.
I will be Interested in reading comments about what I wrote here regarding the `Equivalent Length Method` of calculating the Resistance / Frictional Loss in Gas Pipework.
Whatever the reason that I have seen NO reference to the Method that I described - it would NOT be Correct for anyone to state that: `This does not apply to Domestic Gas Supply Pipework` - or that `The Fittings have been allowed for in the Tables` - or that `There is no need to allow for Frictional Loss / Resistance in Gas Pipework`.
What I have briefly described is the Fundamental Method for Calculating the Pipework Sizes for Gas Pipework Installations.
Regards,
CHRISM - Building Services Engineer and Qualified Gas Engineer - Heating Engineer and Plumber - based in England / U.K.
I have noticed something that SEEMS to be missing from the Table / Calculations / the Answers that You have seen - although Please accept My Apology if I have somehow missed this:
When calculating the Gas Pipe Sizes for within a Building / Home the `EQUIVALENT LENGTH` Method MUST be used - This may be known under a different `Name` in the U.S. - ?
This Method means that as well as the Measured Length of the actual Pipework the `Frictional Loss / Resistance` within the Pipework and Fittings MUST be calculated and Allowed For when using the Pipework Supply Tables.
To be able to do this You MUST know the Number of 90 Degree Bends - Tees etc. that are installed on EACH Section of the Gas Supply Pipework within the Building - and the `Frictional Loss` AMOUNT that has to be Allowed for.
For example here in the U.K. the Tables show the Amount of Natural Gas that can be Supplied from a STRAIGHT LENGTH of Gas Pipe - this is now shown / calculated in Cubic Metres per Hour and Metres of Pipe.
The Gas Pipework Internal System Pressure is [approximately] 21 Millibar [approx. 8"] Water Gauge with an `Allowable` Pressure Drop of ONLY 1 MILLIBAR Water Gauge across the Pipework System.
These figures are obviously significantly different to the 7" to 14" Pressures and the 1" permitted Pressure Drop that LiQuid stated is the `Norm` in Canada [and the U.S. ?].
When Calculating the Gas Supply Pipework it is necessary to Work Out the ACTUAL Length of the Pipework AND Also the `EQUIVALENT LENGTH` - which is the Actual Measured Length PLUS an `Added Length` for the Frictional Loss from the Fittings.
An example of the Allowance / ADDITION for each Fitting here in the U.K. is that each 90 Degree Elbow / Bend and Tee is ADDED as 0.5 Metres [0.3 Metres for a Sweep Bend] TO the actual Measured Length of the Pipework.
These figures are for Small Bore Domestic Gas Pipework.
So - A simple example would be:
If a Pipe that was Supplying only one Gas Appliance actually Measured 12 Metres and had 6 X 90 Degree Elbows / Bends - the `Equivalent Length` would be 15 Metres - having ADDED 3 Metres [6 X 0.5M] to the Measured Length.
The Method is a bit too complicated for Me to write an explanation here / Now - But basically You MUST Know the Total Gas Requirement for ALL of the Gas Appliances - This will govern the Size of the `Incoming Supply` and here in the U.K. the Model of the Meter.
Knowing what the Incoming Supply Pipe will Supply You must calculate EACH Section of the Internal Supply Pipework by actually Measuring the Length of the Pipework then counting the amount of Fittings - 90 Degree Elbows / Bends and Tees and ADDING whatever You find out to be the `Recommended` Frictional Loss / Resistance Factor in the U.S. - I do not know what this is likely to be in relation to these Tables showing the Supply Volume in BTU`s.
EACH Section would be the Actual Measured Length PLUS the Frictional Loss / Resistance Allowance for the Fittings = the `Equivalent Length` - THIS would then be used to Select / Check the Pipe Size from the CORRECT Gas Supply Table.
This Allowance for the `Extra` Metres / Feet of Pipework to allow for the Frictional Loss / Resistance is VITAL in Calculating the Pipework Sizes Correctly / Using the Gas Supply Tables Correctly.
The Total Amount of Fittings within a Home`s Gas Supply Pipework can cause BIG Differences in what these Gas Tables state a certain Length of Pipe will convey to an Appliance and what is actually Available at the Appliance - as the Tables are quoting the Amount of Gas / BTU`s supplied by a STRAIGHT Length of Pipe.
THIS cannot have `Been Allowed For` within the Tables as it would be an `Unknown Quantity` - I also have NOT seen any reference to this in the Answers that You have received.
Although I am a Gas Engineer [U.K.] - amongst other Qualifications unfortunately I cannot be of Help to You about the actual Calculation for your Home / Gas Supply Pipework to your Appliances at present because I am going to be away from Home on Business.
I will not be wanting to do any Calculations in the Evening when I am away - especially those which would require a `Correct` Gas Supply Table from the U.S. and a `Fittings Allowance` reference - and where the `Equivalent Length` Method does NOT seem to be used [?].
Good Luck in resolving Your Questions - while this `Explanation` / Method may not actually help with your Question - knowing more about this Method would help You to actually Calculate the Amount of Gas VOLUME / BTU`s that would be available at the point where the Pipework reduces in size / Where perhaps it should not have reduced to less than 3/4" Pipe - and the BTU`s / Volume that would be available at EACH Tee point and Appliance Inlet - regarding other Appliances.
I will be Interested in reading comments about what I wrote here regarding the `Equivalent Length Method` of calculating the Resistance / Frictional Loss in Gas Pipework.
Whatever the reason that I have seen NO reference to the Method that I described - it would NOT be Correct for anyone to state that: `This does not apply to Domestic Gas Supply Pipework` - or that `The Fittings have been allowed for in the Tables` - or that `There is no need to allow for Frictional Loss / Resistance in Gas Pipework`.
What I have briefly described is the Fundamental Method for Calculating the Pipework Sizes for Gas Pipework Installations.
Regards,
CHRISM - Building Services Engineer and Qualified Gas Engineer - Heating Engineer and Plumber - based in England / U.K.
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These figures are obviously significantly different to the 7" to 14" Pressures and the 1" permitted Pressure Drop that LiQuid stated is the `Norm` in Canada [and the U.S. ?].
Just to clarify, this is dependant on the type of gas used and the supply pressure. ( downstream of the regulator )
And yes, we do use friction losses through various fittings and types of piping etc. to determine the total equivelant length. the question of the Op. was to the effect of
1. If I look at the table, in a house with a 50' run, the most a 1/2" pipe can carry is 73 cf/m (73,000 BTU). But yet my 90,000 BTU furnace is connected with 1/2" line and the furnace is designed to take a 1/2" line. I'm guessing furnaces are routinely connected that way, and mine was permitted and inspected. So what am I missing? Why can furnaces be connected in a way that appears to be a per se code violation?
I wasnt sizing the system, thats Something i'm PAID to do and i dont do it Free or Cheap and am quite maticulous.
Whatever the reason that I have seen NO reference to the Method that I described - it would NOT be Correct for anyone to state that: `This does not apply to Domestic Gas Supply Pipework` - or that `The Fittings have been allowed for in the Tables` - or that `There is no need to allow for Frictional Loss / Resistance in Gas Pipework`.
you are likely going to hate me for saying this but you are in fact not correct here ( according to can/csa-b149.1-05 natural gas and proplane installation code which anybody can verify should they care to check my referance )
article 6.3.2 where it states ( not typing the whole deal so im gonna paraphrase here, do feel free to check this out )
A piping or tubing system supplied at pressures up to and including 14" w.c ( 3.5 kpa ) yada yada yada mostly about allowablle pressure drop as mentioned in my previous posts
( A ) by the use of tables a.1 and a.8 of annex A for natural gas, which include allowance for a reasonable number of fittings, when maximum pressure drop is 0.5 in w.c. ( 0.125 kpa )
^ i should have typed out the ( B ) but its essentially the same table but is allowing 1" wc pressure drop because the supply pressures are for 7-14 inches w.c. on those corrosponding tables and the ones in the ( A ) prevision are the 0-7 " w.c supply pressure.
my point is that they are allowing for fittings. How many fittings do you see installled ina domestic house ? and regardles, does it matter if you are supplying the appliance with enough volume and sufficiant pressure ?
I am required to clock the meter after installation of any new appliance to verify it is operating correctlly.... but I suppose i've typed enough for this sitting .
respectfully, Dm
Just to clarify, this is dependant on the type of gas used and the supply pressure. ( downstream of the regulator )
And yes, we do use friction losses through various fittings and types of piping etc. to determine the total equivelant length. the question of the Op. was to the effect of
1. If I look at the table, in a house with a 50' run, the most a 1/2" pipe can carry is 73 cf/m (73,000 BTU). But yet my 90,000 BTU furnace is connected with 1/2" line and the furnace is designed to take a 1/2" line. I'm guessing furnaces are routinely connected that way, and mine was permitted and inspected. So what am I missing? Why can furnaces be connected in a way that appears to be a per se code violation?
I wasnt sizing the system, thats Something i'm PAID to do and i dont do it Free or Cheap and am quite maticulous.
Whatever the reason that I have seen NO reference to the Method that I described - it would NOT be Correct for anyone to state that: `This does not apply to Domestic Gas Supply Pipework` - or that `The Fittings have been allowed for in the Tables` - or that `There is no need to allow for Frictional Loss / Resistance in Gas Pipework`.
you are likely going to hate me for saying this but you are in fact not correct here ( according to can/csa-b149.1-05 natural gas and proplane installation code which anybody can verify should they care to check my referance )
article 6.3.2 where it states ( not typing the whole deal so im gonna paraphrase here, do feel free to check this out )
A piping or tubing system supplied at pressures up to and including 14" w.c ( 3.5 kpa ) yada yada yada mostly about allowablle pressure drop as mentioned in my previous posts
( A ) by the use of tables a.1 and a.8 of annex A for natural gas, which include allowance for a reasonable number of fittings, when maximum pressure drop is 0.5 in w.c. ( 0.125 kpa )
^ i should have typed out the ( B ) but its essentially the same table but is allowing 1" wc pressure drop because the supply pressures are for 7-14 inches w.c. on those corrosponding tables and the ones in the ( A ) prevision are the 0-7 " w.c supply pressure.
my point is that they are allowing for fittings. How many fittings do you see installled ina domestic house ? and regardles, does it matter if you are supplying the appliance with enough volume and sufficiant pressure ?
I am required to clock the meter after installation of any new appliance to verify it is operating correctlly.... but I suppose i've typed enough for this sitting .
respectfully, Dm
OK, I have cleaned the thread up a little bit, posts that didn't seem to be directed to answering the original question have been removed.
Please keep any future postings on topic and non-personal.
Please keep any future postings on topic and non-personal.
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"Hello phishfood",
I would like to Explain that I was NOT `Personally Attacking` / Deliberately Arguing with LiQuid - regarding Your comment:
Quote: Please keep any future postings on topic and non-personal.
I am SURE that some People will find this explanation `Boring` / Unwanted.
MY view of the Posts that I submitted on here is that:
I initially Questioned whether the `Fittings Allowance` was being applied for the `Equivalent Length` Method of Pipe Sizing regarding the Gas Supply Tables that were being referred to by the Original Poster.
Then after LiQuid had Informed Me that the `Fittings are Allowed For` in the Gas Supply Tables that He was referring to - Canadian Editions - He made a comment about whether this was relevant - words to that effect - which I was trying to Clarify.
I was trying to Explain for the benefit of other readers that the Frictional Resistance of the Fittings on a Gas Pipe DOES `Matter`/ Have a Detrimental Effect on the Gas Volume and Pressure that is available at the Point of Use / Appliance - Relating to what is `Published` in the Gas Volume / BTU Tables.
When the Tables were calculated - as I found out from LiQuid - a certain number of Fittings were `Allowed For` - whatever this `Average Number` is [?] - Just adding a few more / adding the Fittings Allowance to the `Equivalent Length` [as shown in these Tables] WILL lower significantly the Volume of Gas that is `Available` for the Appliance.
Simply just measuring the `Actual Length` of the Gas Supply Pipe and referring to these Tables would NOT be an Accurate Method of Calculating / Checking the Available Volume of Gas - UNLESS the Number of Fittings just happened to be within the `Allowed For Amount` in the Tables.
THAT is the point that I was trying to Explain and that I kept referring to.
The reason that I queried this point originally is that this situation where the `Fittings are Allowed For` in the Gas Supply Tables is NOT the case in the U.K. where there are Different Gas Pressures and a Different / Much LESS `Permitted Pressure Drop` - So We want to Calculate to what is obviously a Higher Degree of Accuracy.
The Number of Fittings on an individual Pipe is an Unknown Quantity - there needs to be a Very Close to Correct Number for Correct Calculation of the Pipe Sizes- obviously on New Builds or Extensive Refurbishments this can usually be Identified to a fair degree of Accuracy from the Drawings.
On Installations to Existing Properties where Gas Pipework did not previously exist the Route would need to be found and the Pipe Run Measured and the Number of Fittings Noted for the Calculations.
I was NOT trying to `Put One Over` on Liquid [English Expression].
Regards,
Chris
