What Is a Rough In Plumbing Diagram and Why Do You Need It?

Adding a bathroom to your home or extensively renovating an existing bathroom, kitchen, or utility room will require a building permit. Whether you are hiring a professional plumber or attempting this as a DIY project, you will be asked to supply a rough-in plumbing diagram. This simple drawing offers the building department a three-dimensional view of your plumbing plans and allows for a much faster and more accurate inspection.

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But rough-in plumbing diagrams are valuable to the homeowner and/or plumber as well, providing a pre-installation plan that helps to uncover problems and brainstorm solutions. This straightforward diagram also provides the plumber (or homeowner) a map of the system and nearly a step-by-step method of installation.

What Is a Rough In Plumbing Diagram?

This particular type of drawing uses lines and symbols to display the layout of your venting and drainage pipes behind the walls and underneath the floorboards. It is usually necessary for the permit application process and acts as a guide during installation.

The linear drawing shows three dimensions, giving the layout depth. This doesn’t need to be complicated. By using angles and symbols you can easily show the three dimensional design, including connections, fittings and sizes of all pipes.

Drawing this diagram may be easier than you think. Experts suggest that by imagining the plumbing layout from above and at an angle you will gain the proper perspective. Use a ruler and a special drafting square that offers 30, 60, and 90-degree angles.

Always draw the connection angles as they will actually appear. For instance, a hard 90-degree turn in your plumbing should be indicated with a 90-degree corner. A 45-degree turn should be accurately drawn with that acute angle, and so on. That drafting square will come in handy when you’re in need of accurate, easily drawn angles.

How Does Your Current Plumbing System Fit In?

Your rough in diagram does not need to include the existing plumbing system. You will specify where and how the new plumbing connects to the existing system, but otherwise those details can be left out. Consider the rough in diagram to be a supplement, adding to the details of the existing system and outlining the proposed changes in a clear way.

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Important Inclusions

Venting is one of the most important elements of plumbing. These pipes provide a pathway for harmful gases to exit your home, preventing dangerous situations from arising. A rough-in plumbing diagram always includes the venting pipes, connections, and fittings.

Venting pipes are marked using a dotted line. The new vent pipes will either be connected to an existing vent system or exit the home with a new exterior vent. Both of those installations can be indicated on the rough in diagram. Show a portion of the existing vent pipes with a clear label marked “existing” and indicating the size of that pipe. For new venting configurations simply include all of the vent pipe in the drawing and it will be understood as a new vent.

Plumbing that carries water, such as drainage pipes, are indicated with a solid line on your rough in plumbing diagram. Drainage is the second important element in your diagram, and required by the permit application process. Be sure to mark all of the places where the new drainage pipes will connect to the existing systems, in the same way that you indicated new and existing venting configurations.

Sizing should also be included wherever possible, from the vent piping to the drainage and so on. The diameter of the plumbing should be clearly marked beside the line and connected with a short arrow and another type of label.

Some permit applications will require the materials to be specified as well. This may or may not be applicable in your circumstance. Take the time to find out and leave out any information that is not required. This will allow your diagram to be clean and clear, as opposed to a cluttered sketch that may be difficult to read.

Samples and Direction

The best place to find samples is straight from your local building department. This allows you to see what type of information is required and how the plumbing inspectors prefer those details to be communicated. Ask for samples from your local plumbing inspector. They may charge a small fee for access, but the time saved is generally well worth the investment.

If you run up against a particularly difficult or unusual situation, a sample may not be helpful. Hire a professional plumber to draw up the diagram, even if you are planning to tackle this project yourself. This investment will provide you with a smoother permit application process and a roadmap for your work. Be aware that plumbers will charge for this service and for any time they spend explaining the drawing to you. This charge covers their expertise and industry knowledge, as well as their time.

A copy of the local plumbing codes is often available in book form or as an electronic document. This publication generally includes samples of rough in plumbing diagrams and may have more information about how to install and design a plumbing system that will meet code.

The rough-in plumbing diagram is an important part of your bathroom, kitchen, or utility room renovation. Take the time to make sure this step is done properly, and hire a professional plumber to draw the diagram if you are not confident. This accurate and three-dimensional sketch acts as a road map for the plumbing inspector and the installer – whether that is the homeowner or a plumber. Posted by: Diana