# Plumbing Math



## nonbutcrack (Jun 9, 2012)

Hello people I have a question, so I'm trying to figure out is it right to use 1.414 or 1.41 x the center to center to figure out the offset distance of a pipe? I've Heard of both ways but of corse the fraction is different when you get your final answer! Thanks


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## deerslayer (Mar 29, 2012)

There is a 10 or 15 page thread on this subject if you wanna search for it.

The simple answer if you want to do an offset with 45's find your center to center distance between the 2 pipes and multiply by 1.414 and the answer will be your center to center length of your piece of pipe that is on the 45 or the travel piece. Subtract your fittings and cut to length.

Someone will be along shortly with a better or another way to do this. Stay tuned to be confused!


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## plbgbiz (Aug 27, 2010)

nonbutcrack said:


> Hello people I have a question, so I'm trying to figure out is it right to use 1.414 or 1.41 x the center to center to figure out the offset distance of a pipe? I've Heard of both ways but of corse the fraction is different when you get your final answer! Thanks


1.414 has always been the standard. Whoever told you 1.41 needs to go back to apprentice school.

The length of the 45deg run is....

C to C = 1.414 x Offset

Always has been, always will be.


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## phishfood (Nov 18, 2012)

The farther the offset, the more numbers you need behind the decimal point. 

If I am doing a 12 1/2" offset with PVC drainage pipe, I use 1.4 and do it in my head. If you are looking at a 35' offset with 3" threaded pipe, 1.414 might not be quite enough.


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## Gettinit (May 9, 2012)

Just multiply by the √2 and you will never have to worry.

Just in case you do not have access to multiply by the sqare root it is 1.41421356


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## deerslayer (Mar 29, 2012)

plbgbiz said:


> 1.414 has always been the standard. Whoever told you 1.41 needs to go back to apprentice school.
> 
> The length of the 45deg run is....
> 
> ...


Unless you doing a huge offset 1.41 will be more than close enough for plumbing. We are installing plumbing not machining rocket parts. I mean seriously can you cut your piping to the thousandth with a portaband or tubing cutter??

On offsets less than 18" it will make very little difference!


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## TC27 (Mar 10, 2012)

I use 1.41 in the field and 1.414 on drawings.


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## rjbphd (Feb 5, 2010)

deerslayer said:


> Unless you doing a huge offset 1.41 will be more than close enough for plumbing. We are installing plumbing not machining rocket parts. I mean seriously can you cut your piping to the thousandth with a portaband or tubing cutter??
> 
> On offsets less than 18" it will make very little difference!


Don't tell Tex Mech that! It'll screws up his rocket building project!


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## plbgbiz (Aug 27, 2010)

deerslayer said:


> Unless you doing a huge offset 1.41 will be more than close enough for plumbing. We are installing plumbing not machining rocket parts. I mean seriously can you cut your piping to the thousandth with a portaband or tubing cutter??
> 
> On offsets less than 18" it will make very little difference!


Agreed but he is preparing to take his JP test in Chicago.

I don't think they are going to care if it works in the field.


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## deerslayer (Mar 29, 2012)

plbgbiz said:


> Agreed but he is preparing to take his JP test in Chicago.
> 
> I don't think they are going to care if it works in the field.


agreed must know 1.414 for JP test


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## nonbutcrack (Jun 9, 2012)

Thank you for the help so far but yes I was wondering for to take the Chicago written test, will I use the 1.41 technique or the 1.414?? The 1.41 is easier but both give you a different center to center distance resulting in a diffrent fractional answer at the end.


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## plbgbiz (Aug 27, 2010)

nonbutcrack said:


> Thank you for the help so far but yes I was wondering for to take the Chicago written test, will I use the 1.41 technique or the 1.414??....





plbgbiz said:


> 1.414 has always been the standard. Whoever told you 1.41 needs to go back to apprentice school.
> 
> The length of the 45deg run is....
> 
> ...





TC27 said:


> ...1.414 on drawings.





deerslayer said:


> agreed must know 1.414 for JP test


You got the answer three times.


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## grandpa (Jul 13, 2008)

The square root of 2 is 1.41421356237. For practical applications, the common round of is 1.414 Remember that even though you do not ultimately cut a pipe to a 1/1000 inch tolerance, as you do your calcs, rounding errors can add up, so prudence is to use the 1.414 throughout a task.


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## plbgbiz (Aug 27, 2010)

grandpa said:


> The square root of 2 is 1.41421356237. For practical applications, the common round of is 1.414 Remember that even though you do not ultimately cut a pipe to a 1/1000 inch tolerance, as you do your calcs, rounding errors can add up, so prudence is to use the 1.414 throughout a task.


Make that 4 times. :thumbup:


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## nonbutcrack (Jun 9, 2012)

You guys are awesome!! Thanks!


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## U666A (Dec 11, 2010)

nonbutcrack said:


> You guys are awesome!! Thanks!


We try... :jester:


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## TX MECH PLUMBER (May 27, 2011)

deerslayer said:


> There is a 10 or 15 page thread on this subject if you wanna search for it.
> 
> The simple answer if you want to do an offset with 45's find your center to center distance between the 2 pipes and multiply by 1.414 and the answer will be your center to center length of your piece of pipe that is on the 45 or the travel piece. Subtract your fittings and cut to length.
> 
> Someone will be along shortly with a better or another way to do this. Stay tuned to be confused!


Rolling 45 offset. Is the thread !!!


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## U666A (Dec 11, 2010)

TX MECH PLUMBER said:


> Rolling 45 offset. Is the thread !!!


That thread will forever be a dark stain on this forum.


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## SewerRat (Feb 26, 2011)

U666A said:


> We try... :jester:


No, we really are...


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## UA25 (Jan 11, 2013)

*Math*

To double check your math you could use a2 +b2=c2 it would give you length of travel and yes you would have subtract your take-offs. To know the end to end measurement for the travel piece.

One other idea might be once you have used 1.414 to determine the length of the travel is to mutiply that answer by .7071 and that should equal the length of legs of the triangle(set & run). Only for a 45 degree triangle is that constant used. 

Maybe that helped or added to the confusion?

Ryan


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## TX MECH PLUMBER (May 27, 2011)

U666A said:


> That thread will forever be a dark stain on this forum.


Not on my part. Maybe the. Aa just eyeball it Guys. Lol


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## plbgbiz (Aug 27, 2010)

U666A said:


> That thread will forever be a dark stain on this forum.


ONE of them.


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