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MEP 2014 Pipe Sizing Calculator

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Message 1 of 12
rlinzmeier0815
7760 Views, 11 Replies

MEP 2014 Pipe Sizing Calculator

I have been working in Revit MEP 2014 with the pipe sizing calculator for my company.  They want me to prove whether Revit's capabilities to automatically size pipe is correct, which would save alot of time.  We typically design hospital and laboratories so anywhere from 100-500 sinks alone per project.  I believe this tool could be a time saver for everyone utilizing it. However, I found a flaw in how it calculates and was wondering if someone has found a solution or could help me work towards a solution.

 

So in short form Revit uses IPC tables to size pipe.  If you set the connectors on the fixture to the correct fixture units and make sure the calculation method on every fixture is the same the system can have the pipe sized.  However, because the theory of Fixture Units when developed by Hunter were for complete large systems, the pipe sizing is incorrect when branching off.  For instance a back to back lavatory gets sized with a 1" HW pipe feeding it.  Per Revit sizing method it is correct.  (Public Lav 1.5 FU x 2 = 3 FU....3FU = 6.5GPM)  However, logic proves otherwise as I know that faucet is 0.5 gpm so at most 1 GPM needed to be supplied.  This line should be 1/2" and not 1".  

 

Sizing solely on fixture units will make the mains correctly because the theory of fixture units was meant for the whole system.  So as of now allow revit to pipe your system will size the mains correctly but branches to fixutres will be incorrect.  Now we could go back and manually change those pipe sizes but to do that for all the fixtures then what time was saved?  It seems like another IF/Then statement needs to be added to the calculator that would override small FU sums and size on a different parameter embedded in the fixture but still utilize the FU for the overall system?

11 REPLIES 11
Message 2 of 12
adam.jw
in reply to: rlinzmeier0815

I am not a plumbing designer, but this very very relavent to my interests (being that I am the Revit manager for my firm).

 

We would also love to get into pipe-sizing in Revit. But your information has given me pause.

 

Since I am not a plumbing designer, if you have the time, could you explain your problem like I am 5 years old?

 

So I get that it will size the mains correctly.

But why does it not size the branches correctly?

 

Side note:

In our firm, instead of piping up EACH device, we have a Host family, with nested Shared families for lavatories/waterclosets (back to back fixtures).

This gives us a single point of connection, and we manually over-ride the fixture unit calc based on what types of fixtures are nested inside the host family.

 

Again, if you could explain a little better (only if you have time), maybe I can help you out (because I may not be a plumbing designer... but I am a wicked good family editor...)

 

 

____________________________________________________
Please give kudos to the MEP Wish List ideas you like, as this will help the Revit development team prioritize functionality additions!
Message 3 of 12
rlinzmeier0815
in reply to: adam.jw

Sounds like we could help each other.  I would like to learn more about the Host families and nested shared families you are speaking of.  Sounds like it could help out.  I typically pipe one, make it a group and paste it all over so i just have to connect the pipes.

 

IPC has fixture unit values for each plumbing fixture.  These units were developed based on probablity of use and water usage among other things.  Fixture units are then converted to GPM using a chart from IPC.  The GPM is then used on a pipe sizing chart for the type of pipe being used.  Using this chart, a predetermined Velocity, Friction for the system is used with the GPM to find size.  This is what Revit is able to do because it is all equation based.  

 

Sizing smaller branches like a branch containing only 2 LAVs doesnt work because simple logic needs to be used. The Fixture value for a LAV is 1.5 for HW and CW.  So 2 of them are 3 FU.  This coverts to 6.5 GPM using the converter table and then equates to a 1" pipe sizing based on 4 FPS and 1"/100FT friction.  However basic logic knows the faucet is going to be 0.5 GPM.  So worst case GPM needed is 1.0.  So a 1/2" pipe would be sufficient.   

 

So Revit calculates correctly but for small Fixture Unit values more logic needs to be used rather than just a calculation from a table and chart.  

Message 4 of 12
adam.jw
in reply to: rlinzmeier0815

In that case then, you should be able to edit the Type properties of your LAV to use a lower default Fixture Unit value.

 

In Revit, the way things works is follows...

 

Here, in a factory content Revit family, a Lavator has a number of "Plumbing Connector"(s)

This Plumbing Connector is hosted to some geometry so you can make pipe connections to it when it is loaded into the project.

The connector is then linked to a number of parameters, indicated by red arrows in the screenshot below (in this case, the domestic cold watter connector):

connectors.PNG

 

These arrows link to the following parameters (again, indicated by red arrows):

parameters.PNG

 

 

 

So, could you lower your "CWFU" value so that Revit sizes the pipe much smaller?

 

 

____________________________________________________
Please give kudos to the MEP Wish List ideas you like, as this will help the Revit development team prioritize functionality additions!
Message 5 of 12
adam.jw
in reply to: adam.jw

Another thing you could do, is set the Flow Configuration of the plumbing connector to be "Preset" instead of based on fixture units, and then apply a GPM you know the LAV will use:

gpm.PNG

____________________________________________________
Please give kudos to the MEP Wish List ideas you like, as this will help the Revit development team prioritize functionality additions!
Message 6 of 12
rlinzmeier0815
in reply to: adam.jw

You could so it pipes the branch correctly.  But the whole system needs the right FU value to size the complete system correctly.  If i have 50 LAVs and instead of using 1.5 I use 0.25 so I get a 1/2" size then instead of getting 75 FU and a 2-1/2" main I get 12.5 FU and a 1-1/4" main.  Which would be incorrect. 

Message 7 of 12

Problem with changing the LAV to a preset value is the whole system has to have the same calculation method for the system to be sized by revit.  Then it doesnt take into account probability of use.  There almost needs to be FU to size the system.  But if the FU is under 10 (or some rational amount)  the pipe be sized on a preset flow basis?

Message 8 of 12
adam.jw
in reply to: rlinzmeier0815

Poop! I've got nothing at this point. Wish I had something better to offer 😞 maybe our resident genius Cadastrophe has some ideas...
____________________________________________________
Please give kudos to the MEP Wish List ideas you like, as this will help the Revit development team prioritize functionality additions!
Message 9 of 12
CoreyDaun
in reply to: rlinzmeier0815


thewrz wrote:

"Poop! I've got nothing at this point. Wish I had something better to offer 😞 maybe our resident genius Cadastrophe has some ideas..."


Whoa there... I think you're giving me quite a bit more credit than warranted!

 


rlinzmeier0815 wrote:

"Problem with changing the LAV to a preset value is the whole system has to have the same calculation method for the system to be sized by revit.  Then it doesnt take into account probability of use.  There almost needs to be FU to size the system.  But if the FU is under 10 (or some rational amount)  the pipe be sized on a preset flow basis?"


Bear with me here as I'm not a plumbing guy either. So in my view, the bottom line is: can you adjust the FU's of the fixtures so that Revit correctly sizes the branch piping? For the purposes of this question, do not consider the impact on the main's sizing - answer as if only the branch sizing matters. Would you be able to get Revit to size it as you would, taking into account the little bits of logic that you need to apply? If you can get to a "yes" answer for this, then maybe there is hope.

Corey D.                                                                                                                  ADSK_Logo_EE_2013.png    AutoCAD 2014 User  Revit 2014 User
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Message 10 of 12
RKLindner
in reply to: rlinzmeier0815

I had quickly looked into sizing plumbing systems via Revit and gave up before I got too far.  The way to size a sanitary or domestic water system is to use paper charts that require interpolation and some intelligence in order to select the proper sizing information and then to also subject the design to personal preference as well as how the overall system is layed out.. ie do I keep that pipe 3/4" with slightly more pressure drop or increase it to 1" for lower pressure drop.  We won't even talk about which code you might be following - IPC, UPC, NSPC just in USA.

 

I find that initially sizing all my domestic water to 1/2" for lavs, 3/4" for urinals, 1 1/2" for wc, etc., printing out my floor plans when my layout is substantially complete and using my trusty red and blue pencils, I can size the systems very fast.  Then I go back into Revit and update the pipes per my markups.  Same goes for sanitary, storm, med gas, etc.

 

Unless I am missing something in the latest version (haven't had time to get into 2014 yet).

Message 11 of 12
Omar1988
in reply to: rlinzmeier0815

Hi,,,

 

I found this discussion during my search on the Internet about the ability of Revit MEP 2014 to size pipes.

 

As I can understand the problem is appear when you are trying to size branch lines, which is connected to one fixture as it is not applicable to use the flow calculated based on FU values to size these branches. I think this problem can be solved by selecting "Match connector size" as a constraint in pipe sizing. then the branch line size will be same to the connector size which is already defined in the family.

 

Message 12 of 12
rlinzmeier0815
in reply to: Omar1988

As we have looked further into plumbing systems in revit we have found there are advantages to utilizing plumbing systems even if revit isnt 100% accurate.  (job security) Still havent solved the small branch piping problem but revit systems are at a 60-75% completion rate.  There are several different aspects that go into sizing a plumbing system and in order to have a program to give us everything we need in order to size correctly they need to add more parameters to size pipes than FPS, Friction and Connectors.  

 

The first question that should be asked by revit when starting a Domestic Water system is "What is your flow test results?"  Where we would plug in static, residual and flow characteristics. 

 

We have found Revit for sanitary piping to be useable only to keep track of DFU's.  The issue comes because revit wants to use DFU's as a sizing method but becomes an issue because many fixtures DFU are lower than pipe size needed for other reasons. I.E. A floor drain in a mechanical room considered as a primary drain would have 4 or 6 DFUs however, will be a 4" pipe outlet in order to keep the trap from drying out.  

 

There will be an article in an upcoming Plumbing Engineer magazine which will document pros and cons of systems in Revit.  

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