Sanitary System Adjustments and Lavatory Connections: Plumbing Design Tutorial

Adjusting Pipe Sizes and Adding P-Traps for Sanitary System Connections

The article provides a step-by-step guide on how to adjust a sanitary system's piping system, with focus on the lavatories. It describes the process of altering pipe sizes and ensuring that the pipes are correctly centered and aligned.

Key Insights

  • The article emphasizes the significance of adjusting pipe sizes in a sanitary system to match the size of the P-trap, specifically giving an example of altering a 3-inch pipe to a 2-inch pipe.
  • It further highlights the use of the 'tab select' function to easily select and change pipe sizes in the system, thereby simplifying the process and saving time.
  • The article also discusses the importance of correctly aligning the pipes, advocating for adjustments to center the pipes with the sinks for optimal functioning of the sanitary system.

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And in the previous video, we went ahead and got most of our system kind of dialed in for this next series of videos—at least for the hot and cold water. We ended up connecting really all the hot and cold water.

What we want to go ahead and do now is start looking at our sanitary systems and reviewing those items. So you can see that I have these different connections here. We have those guys, we have these guys—we’ve already tied in the lavatories and the urinals—or the toilets and the urinals, excuse me—but now we need to go ahead and start tying in the lavatories.

Now, there's a couple of things I want to talk about before we get into that. We need to make some adjustments to our system. Now, if I look at one of these lavatories, I'm going to select my pipe—my P-trap here.

You'll notice that my P-trap is a one-and-a-quarter-inch P-trap. Now, currently though, we have a larger size pipe. So in this instance, I have a three-inch pipe.

In this instance, I have a two-inch pipe. Well, I could go ahead and actually change these pretty easily to match this pipe size. If you recall, a couple of videos ago, we ended up adding in and changing out for this Tee Reducing Sanitary.

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So let me show you a quick way to go ahead and do this. What I could end up doing is tab-select. And when I tab-select, it's going to select the system of all those same pipe sizes up until the next fitting.

If you notice, it goes to this Tee Reducing Sanitary. And if I tab-select over this three-inch one, see how it picks all those? So what I could do is tab-select this, and I could change it to one-and-a-quarter.

And there we go. Or I could leave it at two-inch. Let's go ahead and leave these at two-inch because we'll have a two-inch vent going up.

That'll be fine. So what I can do here is tab-click, and then I could change it.

Two-inch. And there we go. Tab-click.

Two-inch. Tab-click. Two-inch.

If I want to do two at a time, I could do this, but here's the last one. So tab-click, change it to two-inch. Understanding how your tab selection works is actually an extremely helpful tool that you can use to make your life a little bit easier.

If I go over here to my other one—let's say I want to do more at one time—so these are all three-inch ones over here. I can go ahead, hit TAB, click.

I'm going to hit TAB, hold Control, click. TAB, Control, click. TAB, Control, click.

And then TAB, Control, click. So the Control key is adding to that selection set, right? Let me try to do it one more time a little bit faster.

TAB, Control, click. TAB, Control, click. TAB, Control, click.

TAB, Control, click. TAB, Control, click. I'm not picking up this other one because this is the vertical going up to the next floor.

Then I'm going to change all of these just to be two-inch. And there we go. We've made that a little bit nicer there.

Let's double-check our other ones. I believe we should be good. And then I think on these—we haven’t quite tied—we have tied in the classroom sinks.

We just have these last lavatories to do. Let's double-check up here. Make sure these are all the right size.

So these are all two-inch. That's good. That's good.

And these are all two-inch. That's great. We could do this in plan view.

We could do it in section view. It's kind of up to you on how you want to go about it. We could do it in 3D too.

If I do this—select it, right-click, Draw Pipe—again, I want to make sure I'm on that 90-degree. And there we go.

It looks like I missed a couple of P-traps. If you’ve missed a P-trap, there's actually a really easy way to go ahead and fix that. What I'm going to end up doing is select one of these.

I'm going to go up here to my Create Similar. So I've selected the P-trap. I'm going to go to Create Similar, and that's going to put me back into my P-trap command.

Let me get my endpoint. Then I just need to rotate this guy a couple of times. It's in the right location now, but we're not quite centered on our pipes yet.

This one happened to work out because we were centered on that pipe, but we need to go into our plan view real quickly and align these pipes to the centerline of our sinks. Also, by changing this pipe size, we give ourselves a little bit more flexibility in the differences between these fittings so that we can actually make this adjustment. So I'm going to go to my Plumbing 1 Plan and let's see here.

I'm going to go ahead, hit AL for Align, pick there. And I can pick the centerline of the pipe—or I could—it’s going to be kind of tough to get this centerline. So I'm just going to pick the centerline of this pipe.

Tyler Grant

Revit MEP Instructor

Tyler Grant is a BIM Manager a Delawie. A dedicated, goal-oriented, and experienced architect. Tyler has managed multiple design/build BIM projects from inception to construction completion, through all phases. Technology-driven and experienced educator to train and instruct users, both novice and advanced, in the workflow and processes of the modern architecture, engineering, and construction field. 

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