topic Can Revit understand how flow separates when a pipe branches off and reconnects? in Revit MEP Forum

Can Revit understand how flow separates when a pipe branches off and reconnects?

andredelattre — Thu, 17 Aug 2023 14:49:07 GMT

Hi all,

I'm still learning Revit and mostly trying to see how it can handle pressure loss calculations and flow reports.

I created the following setup shown below to see if Revit could predict pipe flow in separating and reconnecting branches. The pipes are well connected and, in both scenarios, form a single cold water supply system. The numbers shown below are the section labels which are relevant to the pressure loss report.

After running a pressure loss report, I noticed the left system behaved somewhat expectedly: the 4 GPM flow through section 2 splits into 2 GPM flow in sections 3 and 1, as shown in the report below:

However, the right system behaves very strangely. Section 6 has a flow associated to it (to supply the sink), but it's not pulling that flow from everywhere: the connected sections 5 and 2 both claim to have 0 GPM of flow going through them.

The same behavior appears right before the top right sink (Section 4) where there is flow, but the connecting pipes sections 3 and 1 don't claim to have any flow. The sinks both have a connector flow direction of "In", so I don't think it's assuming a supply from the sink.

I was wondering if anyone knows whether this is a bug or instead if Revit isn't able to model this? Alternatively, could I be missing something? Thanks in advance for any help or even input on your experience with pipe pressure loss reports!

André

P.S. Notice that this last Pipe Report has a section 9 with a Plumbing Fixture, neither of which actually exist. This report is for some reason seeing 3 separate sinks. However, the report here is looking at Domestic Cold Water 5 (the name of this system), which only has 2 sinks connected to it, further emphasized in the System Browser. However, I doubt this is the cause of the issue but rather another symptom of whatever's causing the problem.

Re: Can Revit understand how flow separates when a pipe branches off and reconnects?

RLY_15 — Thu, 17 Aug 2023 15:19:29 GMT

No, Revit does not handle parallel piping.

It does (sort of) handle the hydraulic separation of Primary/Secondary loop structures, but that's an adjacent use case.

You're going to see this problem come up again in the deployment of sanitary/vent systems - you'll need to include system separation methods in your workflow or the vent piping will create a loop in your sanitary piping which will disrupt waste fixture unit calculation and pipe flow direction.

You may also see this crop up when you connect domestic hot water return into your supply line, depending on how its modeled.

Re: Can Revit understand how flow separates when a pipe branches off and reconnects?

andredelattre — Thu, 17 Aug 2023 15:29:07 GMT

Wow, thanks for the help! I'll definitely keep an eye out for it in the sanitary and venting systems. It's pretty unfortunate that it can't handle parallel piping, especially for sprinkler systems, but I suppose that's not an easy thing to calculate. Thanks again!

Re: Can Revit understand how flow separates when a pipe branches off and reconnects?

iainsavage — Thu, 17 Aug 2023 19:39:53 GMT

There was a previous post about a similar situation with ductwork and a solution(?) involving placing balancing dampers in each branch and assigning flow percentages to them - not sure if that would work for pipes with balancing valves, never tried it.

Re: Can Revit understand how flow separates when a pipe branches off and reconnects?

andredelattre — Thu, 17 Aug 2023 19:42:19 GMT

Interesting, thanks for the info. I'll take a look at it and see if it works for piping.

Re: Can Revit understand how flow separates when a pipe branches off and reconnects?

iainsavage — Thu, 17 Aug 2023 20:14:24 GMT

https://forums.autodesk.com/t5/revit-mep-forum/airflow-through-a-duct-that-splits-into-multiple-taps-then/m-p/11151599