Installing plumbing vent code for waste lines

Installing a proper plumbing vent code system is a requirement. Now, let's move on to Drain, Waste, and Vent systems. Most plumbers now use ABS for these systems because it's so east to use. ABS and PVC is much lighter, less expensive, and more flexible than iron. If your local plumbing code prevents the use of ABS, then you’ll have to use cast iron pipes. Usually though, ABS is an acceptable product to use. plumbing waste


Two types of plastic pipe are ABS and PVC. Both are available anywhere and really inexpensive, but the better of the two is probably the PVC plastic pipe. It is slightly more durable than ABS.

Many plumbers still use ABS because it was the first plastic product for DWV systems and they used it for years. I think that both are great to use.

Plastic pipes are very easy to cut. You can use a saw, or a plastic pipe cutter. An important thing to remember is that when you cut plastic pipes, they leave behind burrs that need to be removed with a utility knife or sand paper on both the outside and inside of the pipe. If you don't do this, junk will catch on the inside of the pipes and the lines will plug up a lot. When you make the DWV layout, you’ll use several different pipe fittings for corners, branches, cleanouts, and traps. You should do a dry run with the fittings and pipes before gluing them.

Once you've made sure that everything fits correctly, you will use the compound and cement them together. PVC and ABS cement is a one-time try. It cements the fittings and pipes together instantly. If you have to get them apart after cementing, you’re probably better off cutting the pipes apart with a saw and putting a coupler in place.

pvc fittings

When you put the pipes and fittings together, make sure they are connected completely and in all the way. This gets kind of difficult when the pipe goes through joists and studs and is fairly hard to reach. A good seal is completely important though. Let’s cover the most common fittings that we use in the DWV system.

pvc elbows

There are several other kinds of connectors and fittings in addition to these, but we’ll just focus on a few of these for now. You don’t want to mix and match ABS and PVC. They are made of different materials and they both use a different type of solvent cement. There's a lot of different variations of fittings because they do specialized things.

An elbow is either a waste water elbow or a vent elbow. The difference is that the vent elbow fitting has a shorter turn radius and the water elbow fitting has a longer turn radius. Air goes around corners a lot easier than water does. Vent pipes can be 1 1/2 inches, but pipes carrying waste water (washing machine, dishwashers, sinks, and baths/showers), have to be 2-inch lines.

Soil pipes carry solids so they have to be at least 3-inch lines. That is the a few of the differences in the sizes and the turn radius of pipes and fittings. Now let’s combine it all to see how they form a good plumbing-vent-code system.

venting diagram

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