NDS Catch Basin Sizes: A Buyer’s Guide
A practical breakdown of one of the most widely stocked residential catch basin product lines.
On this page8 sections
- NDS Catch Basin Line at a Glance
- Why the 6-Inch Round Basin Is the Residential Default
- NDS Terminology on Product Listings
- Accessories Worth Knowing About
- Alternative: Buying a Complete Kit
- 6-Inch Round vs. 9-Inch Square: Which to Start With
- Quick Reference: Size to Typical Use
- Factors to Confirm Before Ordering
NDS is one of the most commonly stocked catch basin brands at home improvement and irrigation supply stores, which makes it a practical reference point when translating a calculated GPM requirement into an actual product to buy. Once the Catch Basin Sizing Calculator gives you a target GPM and footprint, this guide helps you match that number to the closest NDS product.
NDS Catch Basin Line at a Glance
| Product Line | Sizes Available | Material |
|---|---|---|
| Spee-D Basin (round) | 6 in | Styrene |
| Square Catch Basin | 9, 12, 18, 24 in | Polypropylene |
The brand’s stormwater drain lineup spans from a compact 6-inch round basin up through a 24-inch square option, with a range of grate and filter choices across both residential and light commercial projects.
Why the 6-Inch Round Basin Is the Residential Default
The smallest round basin in the lineup is built for exactly the kind of small, single-source drainage most homeowners deal with, such as a downspout or a planted bed low spot. Its compact footprint and simple outlet setup make it the most frequently purchased option for straightforward yard drainage projects, and it’s usually the first size worth checking before moving up to a square basin.
NDS Terminology on Product Listings
| Term | Meaning |
|---|---|
| Outlet Configuration | How many pipe connection points a basin has, such as 1, 2, 3, or 4 outlets |
| Universal Adapter | A fitting that connects a range of pipe diameters to the basin’s outlet |
| Basin Riser | An extension piece that raises basin height to match finished grade |
| Locking Outlet | An outlet type that snaps directly onto corrugated pipe without gluing |
Matching Calculated GPM to a Product Size
Required GPM = Drainage Area (sq ft) × Rainfall Intensity (in/hr) × Runoff Coefficient × 0.623
Compare this result against each product line’s rated per-outlet capacity, and size up to the next available size if your requirement exceeds the smaller option’s rating.
What to Check Before Buying
- Confirm your calculated GPM requirement against the specific model’s rated capacity, not just its footprint
- Check the outlet count and pipe diameter compatibility for your existing drain line
- Decide whether a complete kit (basin plus grate) or separate components better fits your project
Example 1: Single Downspout Project
- Calculated requirement: ~11 GPM
- Product choice: 6-inch round basin, single locking outlet
- Rated capacity: approximately 68 GPM on that outlet configuration
A single downspout’s calculated flow sits well under the rated capacity of even the smallest basin in the line, which is typical for this use case and leaves a comfortable safety margin.
Example 2: Two Downspouts Sharing One Basin
- Calculated requirement: ~20 GPM
- Product choice: 6-inch round basin with a multi-outlet configuration
- Rated capacity: approximately 83 GPM per outlet on that configuration
Multiple outlet configurations exist on the same 6-inch footprint, so combining two downspouts often still fits within the round basin line before a square basin becomes necessary.
Example 3: Driveway Apron Needing a Larger Footprint
- Calculated requirement: ~35 GPM
- Product choice: 12×12-inch square basin, two-outlet polypropylene model
- Reasoning: exceeds the practical range of the round basin line at this flow rate
Once a project moves beyond a single-outlet round basin’s practical capacity, the 12-inch square size is the natural step up for a driveway-scale project.
Get your exact GPM requirement before matching it to a product.
Use the Catch Basin Sizing CalculatorAccessories Worth Knowing About
| Accessory | Purpose |
|---|---|
| Universal Adapter | Connects a range of pipe diameters, from 3 to 12 inches, to square catch basins |
| Basin Riser | Stacks on top of a basin to add height, cuttable to fit finished grade |
| Adapter Plug | Seals an unused outlet on a multi-outlet basin |
Alternative: Buying a Complete Kit
Complete kits pairing a basin body with a matching grate are available across most of the size range, and provide everything needed for a straightforward installation in one package. For a single-basin residential project, a kit is often simpler to shop for than sourcing the basin body, grate, and adapters as separate line items.
Common Buying Mistakes
- Choosing a basin footprint without checking the specific model’s rated GPM per outlet
- Buying a basin and grate separately without confirming they’re compatible sizes
- Assuming every grate option is rated for vehicle traffic, when many are foot-traffic only
- Not accounting for riser height needed to reach finished grade before ordering
- Assuming all outlet sizes are interchangeable without checking adapter compatibility
6-Inch Round vs. 9-Inch Square: Which to Start With
The 6-inch round basin covers most single-source residential jobs at a lower cost, while the 9-inch square basin offers a larger inlet area and more outlet flexibility for combined drainage sources. If a project’s calculated GPM sits close to the round basin’s rated limit, starting with the 9-inch square option provides more headroom without a large cost jump.
Quick Reference: Size to Typical Use
| Size | Typical Use |
|---|---|
| 6 in round | Single downspouts, small landscape low spots |
| 9 in square | Multiple downspouts, larger landscape areas |
| 12 in square | Combined downspouts, small paved areas |
| 18-24 in square | Larger paved areas, light commercial use |
Factors to Confirm Before Ordering
- Calculated GPM requirement compared against the specific model’s rated capacity
- Outlet count and pipe diameter matching your existing or planned drain line
- Whether a riser is needed to reach finished grade
- Grate load class required for the installation location
- Whether a complete kit or separate components better fits the project
Steps to Choose the Right Basin Size
- Calculate your required GPM using your drainage area and rainfall intensity
- Compare that number against the 6-inch round line’s rated per-outlet capacity
- Move to the square line starting at 9 inches if the round basin isn’t sufficient
- Check outlet count and pipe diameter compatibility
- Confirm riser and grate options match your installation depth and traffic needs
- Decide between a complete kit or individually sourced components
Frequently Asked Questions
What sizes do residential catch basins typically come in?
A common lineup includes a 6-inch round basin for small jobs, plus square basins in 9-inch, 12-inch, 18-inch, and 24-inch sizes for larger drainage areas.
What GPM is a 6-inch round catch basin rated for?
A typical 6-inch round basin is rated at roughly 68 GPM per outlet on a single-outlet configuration, or around 83 GPM per outlet on multi-outlet configurations.
Are plastic catch basins rated for vehicle traffic?
Some are rated for light vehicular traffic when properly installed, but this depends on the specific grate chosen alongside the basin, so check the rating before installing in a driveway.
What pipe sizes work with standard square catch basins?
Universal adapters typically allow square catch basins to connect to 3-inch through 12-inch drain pipe, depending on the adapter used.
Can I extend the height of a catch basin after installation?
Yes, basin risers stack on top of the basin and can be cut to size for a precise fit to finished grade.
Should I buy a catch basin kit or separate parts?
A kit is simpler for straightforward single-basin projects since it includes a matching grate, while separate parts offer more flexibility for custom outlet or grate combinations.
Get your exact GPM requirement before shopping.
Try the Catch Basin Sizing Calculator