What Are Plumbing Riser Diagrams?

What Are Plumbing Riser Diagrams?

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First of all, it is important to understand what risers are. In essence, they are pipes, but very specific pipes.

In the given picture, you can see a large waste pipe, and the cold and hot water supply pipes (marked blue and red respectively) leading to the position of the sink, indicated by a line drawing. The position of all of these, and all other relevant piping, will be shown on a riser diagram. However, only the water supply pipe is actually a riser.

The New York City (NYC) Plumbing Code defines risers as water pipes that extend one full story or more and convey water to a group of fixtures (like baths, sinks, showers, and lavatories) or to branches that extend to fixtures on two or fewer consecutive floors. Branches do not include risers, mains water pipes, or stacks, the latter of which are vertical lines of soil (for sewage), waste (water from fixtures and appliances, commonly called gray water), vents (to get rid of harmful gases), or inside conductor piping (for storm water).

However, it isn’t only risers that are included inplumbing riser diagrams, as you can see in Design of Plumbing Systems below. For instance, the NYC Department of Building (DOB) requires stacks to be shown on plumbing riser diagrams even though they are not risers! So too does the NYC Plumbing Code.

The point of a plumbing riser diagram is to separate out plumbing systems for potable water, waste water, storm water, sewage, and so on to be able to identify exactly where the different piping is located and what it is attached to in terms of appliances, drains, other building systems, and so on.

A plumber riser diagram is not necessarily drawn to scale, but it must be accurate enough to clearly show the concept. It is often created as a 2D diagram rather than an isometric 3D or an even more complicated axiomatic drawing.

What it needs to show is how the risers and various other pipes relate to one another and to fixtures, drains, traps, and valves or taps, but with just a series of lines. Water and waste pipes are shown as solid lines while vents are shown as dotted lines.