Pipe Sizing

[Anonymous]

Hi guys 
First of all:  I would like to say a big THANKS to all of you because I've learned lots of things from you.... This community is really good in my opinion!

Now it's the time to ask you another help...

I've got an issue when i want to use the magic "automatic pipe sizing" botton....

Let me explan better... maybe with an example:

I'm working in the UK and for Public Health we use different standard to design pipework for domestic water. (Standard BS 806-3-2006 Domestic Water)

We use Loading Units (LU) (Not Fixture Unit as Revit uses).
For my example I have:
3 wc => 1 LU x 3 = 3 LU 
2 Sinks => 2 LU x 2 = 4 LU

4 Wash hand basin => 1 LU x 4 = 4 LU

So the total is 11 LU.

When I know the Loading Units then it's possible to have the flow rate from a chart. (So I can create an equetion:  Flow Rate= f(LU) from Excel)...
When I know The flow rate then I can also use another Chart and see what is the correct pipe size for my flow rate. (see attached pic).

For my 3 wc the size for the pipe should be 15Ømm (flow rate 0.24 l/s)

then the pipe for 3 wc + 2 Sinks should be 22Ømm (flow rate  0.34 l/s)

then the main pipe for 3wc + 2 Sinks + 1 WHB should be 22Ømm (flow rate 0.42 l/s).

Now.... I know that Revit performs a general conversion from fixture units to flow, using the values found in the 2006 International Plumbing Code (IPC), Table E103.3 (3). But is there any way to use my own eqations to sizing pipes?

I know that I could convert Loading Units to Fixture Units (I did it) but Revit Doesn't use the same charts (Flow rate => pipe size ) that we use in the UK. (see attached pic)
So I must use an equation again.... I guess...

my question is:
How can Revit could understand my equations? What I have to do?.... Put my equations in some parameters or create a macro? I really don't know what I have to do...
I've seen lot of people who have asked  the same question... for example here:

http://forums.autodesk.com/t5/revit-mep/fixture-units-vs-flow/td-p/4302974


... but i can't find a solution....

Please.... give a me hand....

Thanks guysssss!!!!

have a good day.

[Anonymous]

Would it be the end of the world for you if you didn't have revit to automatically size your pipes based on your (or any other) formulas? I ask because as convient as what you want sounds, you have to logically think about what revit can do and what can go wrong. Lets say you initially have 5 fixtures, and a common domestic water pipe going to them. Then, all of the sudden, you add 50 more fixtures and the common pipe will automatically be bigger if it goes as you want it to. What happens to any valves along the way if they have a type for each size? How about the fittings - is there enough pipe length for them to fit? Revit may crash because it won't know what to do - abide by your formula or delete some fittings, valves, or the common pipe in general!

Revit does not know your future intentions and account for them. For me, it would seem easier to just put a pipe in there with a preliminary, guessed size and as the project is more and more finalized, just fine tune the pipe as necessary.

[Anonymous]

Hi Sandleaz,

Thanks for your answer....  

After your answer (which probably is correct), I'm wondering: 
What is the meaning of using the pipe sizing botton for both pipes and ducts so?
It's useless so.... I guess...

What I'm doing now (and what Public Health Engineers do usualy) is:

1) Put preliminary/guessed sized pipes where I can see WHB, Sinks, Showers, etc...

2) Connect these pipes to the common main pipes until the plantroom.

3) print out the floor plan

4) do marks up (put the amount of Loading Unit close to the pipes)

5) Use a chart to find the flow rate for each branch.

6) Use another chart to find the sizes for each branch

7) Go back to the revit model and re-size the pipes, pipe fittings....etc...

And what happen if architects will add (or delete) more WHB, WC, Sinks, etc?
You have to do again the job....

How often Architects/clients change the model? well... we all know how ofter right?

Mechanical and Publich Health are much more than do pipe sizing... but how much time do we spend for it?

Maybe my point of view is wrong.... 

Sorry for it....

Thanks again for your answer Sandleaz...

[Anonymous]

Pipe and duct sizing is a feature that can be used (supposedly) in conjunction with automatically routing pipes or ducts .. or constraining your pipes or ducts sizes to your given criteria. For mechanical it's typically based on pressure drop or velocity criteria when the volumetric flow is known. I've never used the feature as it would take plenty of work to setup the flows correctly (only if you need to add up the flows, if diversity or redundancy or other complicated scenarios are involved, revit won't understand it).

About your comment on the arhitects --- that's something you need to let the architect know, how far in advance they need to select and place their fixtures, how much change may be involved later on, etc.. As long as the architect understands how dependent you are of them, they will hopefully give you good warning in advance and make good decisions early on. A good architect does not go out of their way to wrong the other disciplines.

[Anonymous]

Thanks again Sandleaz...

MEP is definitely dependend from Architects....but this is the job and we all shoud play a good game... but unfortunately sometime we are not a good team...

Btw the only thing that i can do if Revit is useless for the pipe sizing is to combine the points 5) and 6) from my last answer... how?
I will create an equation in Excel from my charts.... and I will see.

At least I will be faster...

Have a good day Sandleaz...

[fabiosato]

You can try Color Splasher from BIM One, this is a plug-in in exchange store, to color your pipes, so you can have a visual hint in 3D views for example.