incomprehensible Flow Vales Result

[SdinizF]

Hello,

I inserted a Plumbing Fixture (Sink) with a pipe conection on Cold Water.

The fixture Unit is 1.0 and the Flow result is 0.95l/s (liters per second).

Is Revit Calculating this values correctly?? It is a lot of water for a simple sink. The water velocity is too high too due the high flow.

I 

[iainsavage]

You need to look at the International Plumbing Code which is what Revit uses.

There are also two calculation methods, one fir systems which use flushing thanks on WCs, the other for systems which use direct flushing valves.

The direct flushing valve option generates a minimum flow of 15 usgpm.(0.95 l/s).

[iainsavage]

[SdinizF]

Thank you a lot for your answer.

In fact the calculations are following the Flushometer Valves parameters of the tabble, less then 5 fixture units result on 15 gallons per minute, but I tested for some Flush Fanks and it worked like valves.

2.2 fu on Flush Tanks resulting in 15 GPM:

On family Editor:

Do you know how to configure it?

[iainsavage · Accepted solution]

It doesn’t matter if the appliance family has a flush tank, you need to edit the properties of the pipe system and change the calculation method from “Predominantly flush valves” to “Predominantly flush tanks”. There are other posts on the same topic.

[robert2JCCH]

We're a bit overdue for either:

-Interpolation of flow at extremely low fixture units

-Revision of fixture unit to flow conversion tables based on prevalence of low-flow fixtures, both from a code mandated and energy conservation perspective.

From a user standpoint, it does get a bit unintuitive that you might need to model a flush valve system as a flush tank pipe system to avoid oversized pressure drop calculations due to terminal fixtures like service sinks and hose bibbs. There's some value in the meantime to build some rough curve-fit tables so that you can compare the total flow for both system cases.

[iainsavage]

I don’t disagree and I’m not endorsing it but that’s the way that the IPC method seems to work. 

I’d never heard of the “International” Plumbing Code until I started using Revit and had the same problem as @SdinizF.

By “International” I think it means USA and Canada?

It would be better if they offered a choice of calculation methods by country etc and I know its possible to create your own calculators but I don’t have the programming skills to do so.

[robert2JCCH]

From the website:

The International Code Council was established in 1994, with the goal of developing a single set of national model construction codes. It brought together three different organizations that had developed three separate sets of model codes throughout the U.S.: Building Offi­cials and Code Administrators International, Inc. (BOCA), International Conference of Building Officials (ICBO) and Southern Building Code Congress International, Inc. (SBCCI).

---

To my knowledge the founding organizations are all US-based, and overseas adoption is actually quite limited... a bit of a misnomer.

The hunter curves don't have a particularly good polynomial or exponential curve fit to plug into a Calculated Parameter, you'll inevitably wind up with ~10% deviation across some portion of the fixture unit range, but it can still be used as a rough check. I'd love to see an updated building study that challenges the original hunter curve in terms of use patterns and fixture flow rates. Till then, local code is local code.

[SdinizF]

My first contact with IPC was last week with Revit, I've studied the norm a bit and understood enough to compare the results with my country (Brazil) rules to dimentionating pipe systems.

The results are around 30% different sometimes and I don't feel comfortable to use them here.

If Revit were more adaptable to other calculation methods it would be awesome. I will contact a developer to ask if he can do it for me.