---
title: "Street inlets: curb vs gutter inlet"
subject: "Sanitary Engineering"
chapter: 4
key: "semester_6/sanitary_engineering:street-inlets-curb-gutter"
source: https://www.bctengineer.com/q/semester_6/sanitary_engineering/street-inlets-curb-gutter
site: BCT Engineering
---

# Street inlets: curb vs gutter inlet

Sanitary Engineering · Chapter 4: Sewer Appurtenances

- Asked in: 2068 Magh (old course), 1+2+3 marks
- Video: [Sewer Inlets | street inlets | Curb inlets | Gutter inlets with diagram |  IN HINDI by EASY CIVIL](https://www.youtube.com/watch?v=KQPGvbz4KE4) — EASY CIVIL
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/sanitary_engineering/street-inlets-curb-gutter
- Whole chapter: https://www.bctengineer.com/md/semester_6/sanitary_engineering/chapter-4

## Question

What do you understand by street inlets? Where are these located? Differentiate between a curb inlet and a gutter inlet.

## Short answer

Street inlets are structures that admit road storm water into drains, located at corners, low points, and 30–60 m intervals. Curb inlets have a vertical kerb opening, less prone to clogging but less efficient on slopes; gutter inlets use a horizontal grating, better on continuous grades but clog more.

## Answer

#### Street inlets
Street inlets are openings or structures that admit storm water from the street surface into the storm drain or combined sewer.

#### Location
- At the **street corners** (upstream of pedestrian crossings) and along the kerb.
- At **low points** and sag points of the road where water collects.
- At intervals of about 30-60 m on a continuous grade, closer when the road is flat and the area is large; also at the **end of a catchment length** where gutter flow exceeds its capacity.
- In the side of the road at the downhill side of junctions, so that water does not cross the intersection.

#### Difference between curb inlet and gutter inlet
| Point | Curb inlet | Gutter inlet |
|---|---|---|
| Opening | Vertical opening in the kerb face | Horizontal opening in the gutter |
| Cover | Open, sometimes with a bar | Cast iron grating |
| Water enters | Sideways, as the gutter water flows past | By falling through the grating |
| Clogging | Less by leaves and paper | More by leaves, paper and debris |
| Efficiency | Good on flat slopes and at sags; loses efficiency on steep grades | Better on continuous (moderate to steep) grades, but some fast flow may skip over the grating |
| Safety | Safe for traffic and cyclists | Grating can be a hazard to bicycles |
| Capacity | Smaller; depends on the depth of water at the kerb | Larger when the grating is clear |
| Suitable for | Kerbed roads on flat grades, sag points and where debris is heavy | Roads on continuous grades with little debris |

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Where are street inlets located?
   A. At street corners, low points and every 30-60 m on a grade
   B. Only at hilltops
   C. Only inside buildings
   D. Only at the end of the sewer
   Answer: A. Corners, sags and regular intervals are where water collects. (Key point: Location)

2. How does a curb inlet differ from a gutter inlet in opening?
   A. Curb inlet is horizontal; gutter inlet is vertical
   B. Curb inlet has a vertical opening in the kerb face; gutter inlet has a horizontal opening in the gutter
   C. Both are vertical
   D. Both are horizontal
   Answer: B. Curb is vertical in the kerb; gutter is a horizontal grating. (Key point: Opening)

3. Which inlet is more easily clogged by leaves and paper?
   A. Curb inlet
   B. Neither
   C. Gutter inlet
   D. Both equally
   Answer: C. The horizontal grating collects debris. (Key point: Clogging)

4. Which inlet can be a hazard to bicycles?
   A. Curb inlet
   B. Drop manhole
   C. Catch basin hood
   D. Gutter inlet grating
   Answer: D. Gratings in the road surface are a hazard for cyclists. (Key point: Safety)

## Related in Sanitary Engineering

- [Street inlets and their types](https://www.bctengineer.com/question.md?key=semester_6%2Fsanitary_engineering%3Astreet-inlets-types) — Sanitary Engineering, chapter 4, asked 2×
- [Street inlets and catch basins](https://www.bctengineer.com/question.md?key=semester_6%2Fsanitary_engineering%3Astreet-inlets-catch-basins) — Sanitary Engineering, chapter 4

## Related in other subjects

- [On-street vs off-street parking; kerb parking geometry](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Aparking-onstreet-offstreet-comparison-geometry) — Transportation Engineering II, chapter 1