The size of the drain pipe for a kitchen sink is an important consideration when installing or replacing a kitchen sink. Using the right sized drain pipe helps ensure proper drainage and prevent clogs or leaks.
The standard drain pipe size used for most residential kitchen sinks in the United States is 1.5 inches in diameter. This size drain pipe allows for adequate water flow for typical household use while still fitting in the confined space under most sinks.
The number of sink compartments, type of garbage disposal if one is used, flow rate of the faucet, and existing plumbing in the home all impact the ideal drain pipe sizing. While 1.5 inches is the most common, some scenarios call for 2 inch drain pipes to allow for maximum water flow. Consulting local plumbing codes is always a smart idea as well.
Drain Pipe is Needed for a Kitchen Sink
The most common drain pipe size used for kitchen sinks is 1.5 inches. However, several factors like the number of compartments, garbage disposal, flow rate, and existing plumbing can impact the ideal size. This comprehensive guide examines how to determine the right drain pipe size for your kitchen sink.
Why Drain Pipe Size Matters
Choosing the wrong drain pipe size can lead to:
- Clogged drains and slow water drainage
- Leaks and water damage
- Noisy pipes and gurgling sounds
- Poor performance of garbage disposal
The key is matching the drain pipe size to the expected water flow rate. An undersized pipe will bottleneck drainage. An oversized pipe wastes money and takes up precious space under the sink.
Standard Kitchen Sink Drain Size
The standard kitchen sink drain pipe size used in most homes is 1.5 inches. This size is suitable for:
- Single bowl sinks
- Double bowl sinks
- Sinks with a garbage disposal
A 1.5 inch pipe allows adequate water flow for typical residential kitchen use. It fits nicely under standard kitchen sinks.
Kitchen Sink Drain Pipe Kit
A kitchen sink drain pipe kit contains the parts needed to install drainage pipes under a kitchen sink. Kits include drain pipes, P-traps, tube extensions, gaskets, and pipe fittings. The most common diameter for kitchen sink drain pipes is 1 1⁄2 inches. Kits are made of materials like plastic polypropylene or chromed metal.
Here is a comparison of some kitchen sink drain pipe kits:
| Brand | Diameter | Material | Length | Price |
| Tovinanna | 1 1⁄2″ | Plastic | 16 inches | $12 |
| Meitianfacai | 1 1⁄4″ | Plastic | 16 inches | $15 |
| Oatey | 1 1⁄2″ | Plastic | Adjustable | $20 |
| Kohler | 1 1⁄2″ | Metal | Adjustable | $30 |
So in summary, standard kitchen sink drain kits contain 1 1⁄2” diameter pipes and fittings to connect the sink to the drain line. Kits come in plastic or metal for adjustable lengths under $30 USD.
When to Use 2 Inch Drain Pipes
Use 2 inch drain pipes for:
- Commercial kitchen sinks
- Multiple compartments
- High flow rate faucets
- Long drain pipe runs
The extra capacity allows for maximum drainage. It prevents bottlenecks with heavy water flow.
Sink Drain Pipe Size In Wall
The standard diameter for a sink drain pipe in the wall is 1.5 inches. This 1.5 inch pipe matches most single and double bowl kitchen sinks. It allows adequate water flow for typical residential use. Many plumbing codes also specify 1.5 inches as the approved size.
Using a 2 inch diameter drain pipe in the wall benefits sinks with high flow rates. Examples are industrial sinks, multiple compartments, or commercial kitchens. The extra capacity prevents drainage bottlenecks with heavy water usage.
Oversized piping wastes money if not needed. Carefully evaluate the expected water flow before sizing up. Proper installation maintaining slope for gravity drainage also remains crucial.
Factors Impacting Drain Pipe Size
Consider the following factors to determine the ideal drain pipe size:
Number of Sink Compartments
- Single compartment – 1.5 inches
- Double compartment – 1.5 inches
- Triple compartment – 2 inches
More compartments increase potential simultaneous water flow.
Garbage Disposal
Units add debris and air bubbles that take up space.
- With disposal – 1.5 inches
- Without disposal – 1.5 inches
Drain Pipe Length
Longer pipes have more friction limiting flow.
- Less than 12 feet – 1.5 inches
- More than 12 feet – 2 inches
Faucet Flow Rate
Higher flow demands more capacity.
- Standard faucet – 1.5 inches
- High flow faucet – 2 inches
Existing Plumbing
Match size to other drains. Avoid bottlenecks.
Are All Kitchen Sink Drains The Same Size
The standard diameter for a sink drain pipe in the wall is 1.5 inches. This 1.5 inch pipe matches most single and double bowl kitchen sinks. It allows adequate water flow for typical residential use. Many plumbing codes also specify 1.5 inches as the approved size.
A careful evaluation of the anticipated water flow is essential before opting for larger pipe sizes. Venting a kitchen sink under a window can further optimize the overall functionality and efficiency of the drainage system.
Pipe Material Options
ABS and PVC plastic pipes are common. Plastic is easy to install and inexpensive but less durable than metal.
Plastic Drain Pipes
- ABS (acrylonitrile butadiene styrene)
- PVC (polyvinyl chloride)
Consider galvanized steel for a super durable pipe.
Brass and copper pipes are durable but expensive.
How to Measure Pipe Size
The nominal pipe size refers to the inside diameter. A 1.5 inch pipe measures 1.5 inches across the interior hole.
Pipe sizes are labeled with a nominal size and schedule rating. The schedule rating indicates wall thickness. Thicker walls make pipes stronger and more soundproof.
Common kitchen drain pipe specs:
- 1.5 inch drain – ABS Schedule 40
- 1.5 drain – PVC Schedule 40
- 2 inch drain – PVC Schedule 40
Installing New Drain Pipes
Follow these steps when replacing or installing new drain pipes:
- Shut off water supply
- Disconnect pipes, disposal, and sink strainers
- Measure space under cabinet
- Dry fit pipes, traps, joints to test alignment
- Cut pipe to needed lengths
- Assemble fittings and pipes with primer + cement or Teflon tape if using plastic or steel
- Attach strainers, disposal, etc
- Check for leaks
- Turn water back on
Getting measurements right is crucial for proper slope and alignment. Avoid kinks or dips that prevent good drainage.
Drainage Code Requirements
Kitchen sink drain pipes must meet plumbing drainage codes. Improper installation can allow sewer gases to enter the home.
Key requirements per the International Plumbing Code (IPC) include:
- Air gaps fittings on dishwasher drains
- Minimum 1/4 inch per foot slope
- Smooth interior surfaces
- No leaks
- Proper cleanout access
Check local regulations for any additional rules in your area. Most require passing inspections on plumbing work.
Signs of Improper Drainage
Watch for these red flags if your kitchen sink drainage seems slow:
- Standing water in sink
- Gurgling noises
- Leaks under the sink
- Strong sewer gas smell
- Slow-draining water
- Clogged drains
Fixes may be as simple as snaking the drain. But an undersized pipe should be replaced.
FAQs – Common Drain Pipe Questions
Does drain pipe size include the tailpiece?
No. The tailpiece is a separate short piece that connects the sink strainer or disposal to the drain trap. It is typically 1.5 inches.
How much slope is needed per foot?
Drain pipes should slope 1/4 inch downward for every horizontal foot. This allows gravity drainage.
Can I use a 2 inch drain with a 1.5 inch wall pipe?
Yes, use an adapter fitting to transition from 2 inch to 1.5 inches. Avoid bottlenecks.
What is the standard kitchen sink drain trap size?
The most common is a 1.5 inch drain trap. Use a 2 inch trap with a 2 inch drain pipe.
Conclusion
Choosing the proper drain pipe size for a kitchen sink is important for adequate water flow and preventing clogs. The standard size used for most residential kitchen sinks is 1.5 inches in diameter. This accommodates drainage from a single or double bowl sink, with or without a garbage disposal.
In some situations, increasing to a 2 inch diameter drain pipe is beneficial. Examples include commercial kitchens, sinks with multiple compartments, and long drain pipe runs exceeding 12 feet. Consider factors like existing plumbing, faucet flow rate, and garbage disposal when deciding on the ideal drain line for your kitchen sink installation.
More Information: Home Page
