If you need to replace or repair any issues with your home’s drain and sewer system or are adding to your plumbing system, it’s essential that you get the correct type and size drain. When it comes to drains, there are far more options than you may realize. As such, it’s important that you consider the following factors and ensure you trust the job to an experienced professional if in doubt.

1. Size of Drain and Drain Pipe

When replacing or installing any type of drain, one of the first steps is determining what size pipe you need. Different types of drains have different requirements in terms of how many gallons of water they need to be capable of handling per minute. For instance, a floor drain in a basement or garage generally needs to be able to handle more water than a sink drain. If any drain pipe isn’t large enough, you’ll have issues with water draining more slowly than it should. That’s why there are general rules as to what size of pipe you need for different types of drains.

Choosing the Right Size for Your Drain

Residential bathroom and sink drains normally have either a 1.25-inch or 1.5-inch drain pipe, but a large, deep kitchen sink may sometimes instead have a 2-inch drain pipe. Another thing to consider in terms of a kitchen drain pipe is whether the kitchen has a dishwasher. In this case, you always need either a 1.5-inch or 2-inch pipe since the dishwasher discharge hose is connected directly to the drain underneath the kitchen sink. Shower, bathtub, washing machine, and floor drains always require a 2-inch pipe, while toilet drains are always at least 3 inches or even 4 inches in some cases.

In terms of sink drains, you sometimes have the option to choose either a 1.25- or 1.5-inch pipe. It all depends on the size of the pipe located behind the wall. The tailpiece on many sink drains that sticks down below the sink is often only 1.25 inches. In this case, you can use a 1.5-inch x 1.25-inch washer to connect the tailpiece to a larger P-trap and drain pipe to reduce the chances of the drain getting clogged.

However, this is only possible if the drain pipe within the wall is also 1.5 inches. That’s because you can always step up in size, but you can’t step down. Even if it was allowed, you’d end up creating a restriction that prevented the sink from draining properly and would also lead to the drain constantly getting clogged. That means if the drain pipe sticking through the wall underneath the sink is only 1.25 inches, you need to make sure you choose a sink that also has the same size drain.

2. Type of Drain Pipe

Drain pipes are made out of a variety of different materials. The most common options used nowadays are PVC and ABS, but you can also find copper, cast iron, brass, galvanized steel, and stainless steel drain pipes. Generally speaking, it is almost always better to match like for like. That means if the rest of your home’s drain system is PVC or ABS, you want to choose the same material when installing a new drain or replacing an existing pipe.

Connecting Different Pipe Materials

While you can connect PVC and ABS together, it requires a special connector instead of just being able to glue the pipes together or use a screw connection. One time when you’ll commonly see two different types of pipes connected together is in an older home that mostly has the original cast iron drain system. In this case, you almost always want to use PVC pipes when making any changes to the original drain system.

The main reason is that PVC lasts longer and is more durable. It’s also fully resistant to corrosion, unlike cast iron. The inside of a PVC pipe is also completely smooth so that everything drains through the pipe easily. Cast iron pipes are more likely to clog partly as a result of corrosion and also because the inside often isn’t entirely smooth, which can result in solids getting stuck.

PVC vs. ABS: Which Should You Choose?

For most residential situations, either PVC or ABS is always going to be the best choice. If you’re not sure which type of pipe your home has, you can easily tell by the color since PVC is almost always white and ABS is almost always black. ABS is typically a bit cheaper while also being slightly stronger and more resistant to impact damage than PVC. Nonetheless, it tends to become brittle over time and may only last for 30 to 40 years.

PVC pipes, on the other hand, can potentially last for 100 years. Another issue with ABS pipes is that they can be noisy, meaning you can easily hear water flowing through them since the pipe doesn’t really muffle the sound. That’s why ABS is more commonly used for underground drain pipes outdoors. PVC is far better at muffling sound, which is one of the many reasons why it’s usually the preferred choice for indoor drains.

Choosing the Right P-Trap for Your Sink

When choosing a P-trap for your bathroom sink drain, you may also want to consider what type of sink you have and whether the trap is exposed or hidden. If you have a vanity sink where the trap is hidden in the cabinet underneath the sink, a PVC trap will usually be the best choice due to the cost. If you have a pedestal sink where the trap is exposed, you may instead want to consider a chrome-plated trap for aesthetic reasons. While we said that you generally want to choose like-for-like materials, there is no issue with connecting a chrome-plated trap to a PVC or most other types of piping.

3. Building Code Regulations

While the above factors are important, the most important thing is to make sure that whatever drain option you choose conforms to all of the local building code regulations. The regulations for commercial buildings are often much stricter due to the need for commercial buildings to have adequate fireproofing. That means there are some cases in a commercial building where you can only use certain types of metal piping such as copper or stainless steel.

Common Building Code Requirements for Drain Sizes

For residential buildings, you generally have a much wider range in terms of what materials you can use within a building and for the underground drain and sewer system. The main regulations you need to be aware of mostly concern the minimum size of drain pipe that different plumbing fixtures are required to have. Making sure you understand and follow all of the necessary code requirements when it comes to your home’s drain, sewer, and plumbing vents can help you avoid major hassles and expensive repairs in the future, and the best way to do so is to always hire a licensed, experienced local plumbing service.

Contact Knoxville’s Trusted Plumbing Team

Tennessee Standard Plumbing is an industry-leading company providing exceptional plumbing, drain, and sewer services throughout the Greater Knoxville area. Our team of licensed plumbers has years of experience in the full range of plumbing services and is ready to expertly handle all of your installation, replacement, repair, and maintenance needs. Whether you’re dealing with a leaky drain pipe or any other issue with your drains, give us a call and we’ll ensure everything is done quickly and correctly from start to finish.

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