Sanitary Waste and Vent Piping

[vewright]

A typical plumbing fixture connects into an individual stack or riser. The oulet of the fixture trap connects to the side inlet of a sanitary tee. The bottom outlet of the sanitary tee drains, via an intermediate pipe, into a waste line. The top outlet connects, via intermediate piping, to a vent line or vent stack. Revit has two system classifications and types for sanitary systems--sanitary (waste) and vent. In the real world, vent systems and waste systems are connected at each fixture. However, Revit does not seem to recognize this fact.

If you connect a fixture to the waste system, starting at the fixture, Revit will correctly assign the piping to the sanitary classification and system type. The easiest way to connect the fixture, in my experience, is to select the trap arm outlet, right click, and "Draw pipe" to the main. This places an elbow between the trap arm and the drop to the main. Then, select the elbow, and convert it to a tee by clicking the top plus sign. However, if you select the tee and "draw pipe" from the top outlet of the tee, it will be assigned the sanitary system classification and type, not vent. You can select Pipe from the ribbon, set the system type to Vent, and draw the vent pipe from the top outlet of the tee. So far, so good.

Sooner or later, however, Revit will change the vent piping you just drew to Sanitary. If you use filters to show the sanitary piping as solid lines, and vent piping as dashed lines, all of the vent piping will be rendered in solid lines. Similarly, if you use a pipe tag that includes the size and system abbreviation, all of the piping will be tagged as sanitary.

The only way I have found to get around this problem is to leave a gap between the tee and the vent pipe. That is, the sanitary waste and vent systems have to be isolated from each other.  

You could edit the tee families to assign the top connector to the vent system type, but you also need tees that do not connect to the vent system, and some plumbers use sanitary tees in the vent system instead of vent tees.

This is a pain. There needs to be an easier way to interconnect systems.

On another note, Revit provides the family category of Mechanical Equipment. Mechanical is a broad term, but to many in the AEC world, it usually means HVAC. The problem here is that by default, plumbing equipment (water heaters, circulators) and HVAC equipment are lumped together under Mechanical Equipment. To my knowledge, you can't define new family categories, and the only logical alternative category for a piece of plumbing equipment would be plumbing fixtures. The point is, you need to be able to turn off the HVAC equipment on plumbing views, and vice-versa. To deal with this, I set up an Equipment Type project parameter, which allows me to sub-divide the mechanical equipment category.

[Anonymous]

When you got to draw the vent pipe, draw a small segment to remain "sanitary", add a coupling and then draw the vent pipe.  They should stay separated between waste and vent.

[vewright]

A coupling does not isolate the vent system from the sanitary system. If you
draw the vent pipe from the top opening of the sanitary Tee, by selecting
the opening, right clicking, and selecting "Draw pipe," it will be drawn as
part of the sanitary system. If you draw a short pipe segment, and insert a
coupling, the coupling will be part of the sanitary system. If you continue
with another pipe segment, it will be part of the sanitary system.



Note that you can pick Pipe from the ribbon, change the system type to
Vent, and begin drawing from the top opening of the sanitary Tee, and it
will be part of a vent system. However, if you change that vent pipe
segment to Sanitary, deliberately or accidentally, and then try to change it
back to Vent, you will change the sanitary system to Vent as well.



Revit is a modeling system. However, its strength is not 3D modeling, but
the integration of a wide range of properties with the 3D objects, and the
transparent propagation of changes to those properties between graphic
views, schedules, etc. But, in this instance, Revit does not do a great job.
If all you want to do is make 3D models of piping systems, the behavior
described above is not important. However, many, if not all states, require
the submission of approval drawings to get a plumbing permit. Those drawings
have to clearly distinguish waste piping from vent piping. In our state, we
submit a plumbing plan, and a waste and vent isometric. The isometric
drawing is key, because it is difficult to distinguish the two systems in
plan view. By using filters, and designating piping as waste (sanitary) or
vent, you can quickly generate an isometric view showing the waste piping
with solid lines and the vent piping with dashed lines. If you have to move
a fixture, or change the piping, you can do so in a plan or section view,
and the isometric will change automatically. So, it is frustrating to pull
up the isometric when you think you are done, and find that all of the vent
piping has changed to solid lines.



Vewright

[derxaj]

Has anyone found a solution to this issue, or has anyone from Autodesk addressed this problem?

[asommer]

You could duplicate some fitting families, change the connectors from "fitting" to the proper system type, Link the two sanitary connectors and have the vent connector by itself.  This can get very complicated though.  I had a similar situation with Domestic Hot Water, I had a Recirculating system and had to create a "Special" Tee to separate it from the system and get the calcs to work.  for that reason, I utilize "Pipe Types" to separate Waste from Vent and create a filter to display them differently.  I cannot use the sizing calcs, but that gets done manually here anyway.

[SteveKStafford]

You could review this BLOG post to see the approach described there.

[derxaj]

The issue described in the blog/video is not exactly the same as discussed in this forum.  Has anyone from Autodesk ever responded to this problem or offered an offical soultion?  

[SteveKStafford]

The blog post focus is on the fixture units calculating properly but it's really all the same problem, sanitary and vent system documentation/behavior. The solution for now is to break the two systems so they don't interfere with each other. As describe in the blog post, putting a cap between the sanitary and vent pipe sections doesn't really harm the model and allows the fixture count (and pipe appearance) to maintain their own integrity.

No, Autodesk has not resolved the issue yet, as of Revit 2015.

Alfredo wrote a reply to another thread (at RevitForum) about a carrier family which might offer another solution. I don't recall whether the family manages to propagate the fixture units properly when vent pipe is connected or what my post describes is necessary.

[bvm76]

Have you tried creating a piece of element which has sanitary connector and vent connector? I always start to draw a pipe from this element and never insert it to break a pipe run.

[emm]

It is not ideal, but the only way I have been able to succesfully keep my piping in order "graphically" is through the use of worksets. I have a workset for sanitary, vent, storm, domestic water, plumbing equipment (fixtures, drains, etc.), natural gas, and others on a project by project basis. I then created filters for the vent and plumbing equipment worksets that I use to control the visibility of the pipes / fixtures. This is not ideal, as my vent piping is technically on the sanitary system, but it allows me to create drawings that look nice.

You could say that I use worksets in a similar way as one would use layers in AutoCAD. I also do my calculations outside of Revit, so I am not sure what kind of impact this has on Revit's calculation features.

I hope this is a helpful work around... It seems to me that the best way to work with Revit is to work around it...

[Anonymous]

My two cents:

Unless you are using Revit for sanitary vent pipe sizing (I doubt anyone does), I see no reason at all to use a separate vent system for the vent piping. I set my projects up with a sanitary vent pipe type, which I use for all vent piping in the sanitary system. I also use a template that includes one simple filter that applies the typical dashed line type to the vent pipe type. So other than just using my san-vent pipe type when modeling my sanitary system, it's just a quick application of the template to my sanitary views. This setup does require modifying a pipe tag for the vent piping that references the pipe type as opposed to the piping system abbreviation.

This setup has worked great for me. I doubt Revit will ever be used to size sanitary vent piping. The fact that the venting method used in your sanitary branch or fixture layout will have greater influence over the size of the vent, not the drainage fixture unit count, Revit still has a long way to go before real sanitary vent sizing is available.

[chrisplyler]

I just use a dedicated vent pipe type and accepting that it's still on the sanitary system. It's annoying, but that's what I do.

[Anonymous]

I ususally draw the sanitary pipe from the trap and elbow down to start the stack.  Then click the "+" sign on the elblow to create a sanitary tee and draw that up the ceiling.  Then from a 3D view, I click vent pipe from the sanitary tee and drag it up vertically a little bit to create a space and then change the system type to vent from sanitary.  Then I drag and connect back to the sanitary tee, and it doesn't affect the sanitary system.  This has worked well for me, and with the added feature of "divide system", I rarely cause a global headache.

Another method I have used works well if you don't use plumbing fixtures in the MEP model, and just reference those from the architectural link.  I would have plumbing fixture families for all fixture types, but they would be very simple with minimal graphics, and only have sanitary, vent, and trap connections.  I would copy these around at all of my fixture locations, and they would already have the correct size, fixture units, and systems ready to go.  

Both these methods work well with copying the assemblies around to save time.  I thought about saving these assemblies as "groups" in revit, but the systems tend to go "undefined" once the group is loaded.  

[CharlesGoin]

The reason is for visibility and view filters. Also san/storm is sloped and vent is not. 

Revit really needs to fix this I have a system that is broken everyway I can and STAYS San.. if I check the broken section to a different system, try to remove it.. etc.. etc.. etc.. it changes all that system to vent. 

Hopefully this is better addressed in 2017. 

[CharlesGoin]

Problem I run into is when I am going behind an engineer and all his systems are screwed up and I want to break the system. Even the divide system doesn't seem to break the interconnection of the pieces in teh system I broke. Neither does deleting elbow so the vent system isn't even physically attached to the other system anymore. Still won't let me change it. 

[fabiosato]

Hello,

You need to remove the fitting and then divide the system

[CADmonkey_UK_Building_Services]

Hi,

This problem affects other services, too. HVAC pipework with Bypasses, for example.

The fix is simple: change the connectors' Classification in the Family editor.

Classifications have 3 settings that are not named after a specific service: Global, Fitting and Other. If you right click the fitting you're using and edit the family, you'll notice that all the connector classifications are set to 'Fitting'. Change the middle one to 'Vent' and the others to 'Global', save it as new family with a suitably obvious name and load it in. You won't need that many 'special' fittings and it takes moments.

TBH, although it works perfectly for me, I don't truly understand the differences between Global, Fitting and Other, I just try different things until it works.

A problem with existing fittings getting redefined this way is they seem to have a habit of holding on to their old ways. You have to Tab-select until you can select the System, delete it (which makes the system 'undefined'), and then add a scrap piece of pipe with the system you want. Sometimes you have to delete multiple systems in this way. Eventually it works!

I should point out that I don't produce anything in Revit for any kind of engineering Analysis; all my pipes systems are joined up but I only really do all this to make my Annotation Tags display the right Systems. I'm only interested in spatial coordination and Installation drawings.

[vewright]

This isn't a reply, but a continuation of my original post. In answer to one post, NO, Autodesk has not made a comment that I am aware of. 

I opened the generic coupling family, saved it as a "separator coupling". Both connector elements were set to FITTING. I changed one to SANITARY, and the other to VENT. If I place the separator coupling at the end of a sanitary pipe, I can then pick the other end and select DRAW PIPE to draw the vent pipe. I can change the sanitary section to vent and back, and the vent section is not affected. When I attach the separator coupling to the end of a sanitary line, it appears that Revit orients it correctly. However, if you insert it into a sanitary line, the results are uncertain.

Notice that the FITTING connector type allows the system type to propagate through the fitting--the fitting assumes the system type of the pipe connected to it. The separator coupling doesn't have this flexibility. If I connect pipe to both sides, and then change one of them to, say, Hydronic Supply, the pipe disappears. BTW, changing both connectors to GLOBAL doesn't work. The system type will be the same on both sides.

Needless to say, my separator coupling only works with VENT to SANITARY connections. I will have to create another coupling to connect a BYPASS line, for example, into a SUPPLY/RETURN network.

Now, on to another topic--Mechanical Equipment,. Revit still insists on lumping HVAC equipment and Plumbing equipment together. Now, if Revit did offer separate categories for HVAC and plumbing equipment, I would also want a Process equipment type, and so on. I set up a MECHANICAL EQUIPMENT TYPE project parameter that I can use to identify a piece of equipment as HVAC, PLUMBING  or anything else. Then I use filters to hide or show the type I select for a view. This approach works, but it seems that Autodesk should be able to come up with a more elegant solution.

Another topic: Revit allows you to connect one pipe to another with a TEE or a TAP. That's fine for most piping systems, but it's not enough for sanitary waste lines. You frequently need to connect one waste line to another with a WYE, or a combination WYe & 1/8th BEND. Yes, if you start far enough away from the line and draw the branch at a 45 degree angle, Revit will make the connection with a WYE fitting--SOMETIMES. At other times, it draws a fitting that I have never seen it a fitting catalog. Actually, I believe it's trying to draw a WYE, but since it apparently can't determine the flow direction, it draws it facing the wrong way and makes a 135 degree connection instead of a 45 degree connection. BTW, why can't Revit determine the flow direction when the line already contains tees or wyes that are properly oriented?

[CADmonkey_UK_Building_Services]

I didn't make it clear in my previous post that it's the T-fittings I'm modifying, not the Couplers/Union pieces. Couplers have a habit of disappearing if you edit the pipe in some ways.

So I have a 4" rising stack, branch off to the side so it creates a Tee-piece, then I change the T-piece to my Custom Tee with 'vent' as the middle connector class. With the fittings I use, you can change the branch angle to say 45 degrees by pulling the branch pipe up in an elevation view. I have a few customised Valves also that I use for Flow/Return bypasses.

Re: Wyes - If you join two pipes at 45degrees, what happens when you click the little '+' sign on the elbow?

Re: Mech / Plumbing Equipment: Isn't it all 'mechanical' equipment, as in, it has moving parts? A pump on a drainage system is still Mechanical and you might get the same pump used for other services. A motor driven valve would be a Pipe Accessory.

[AzWoodWarrior]

Got so tired of the water heater being under MECH I made my own! At first it wouldn't let me call it water heater, so I have to call it hydrologic temperature increaser. Take that!