---
title: "Double ring versus single ring infiltrometer"
subject: "Engineering Hydrology"
chapter: 3
key: "semester_5/engineering_hydrology:double-ring-advantages"
source: https://www.bctengineer.com/q/semester_5/engineering_hydrology/double-ring-advantages
site: BCT Engineering
---

# Double ring versus single ring infiltrometer

Engineering Hydrology · Chapter 3: Hydrological Losses

- Asked in: 2079 Bhadra, 4 marks
- Video: [Using a Double Ring Infiltrometer for Soils](https://www.youtube.com/watch?v=YawF0W8PBA0) — SoilSNE
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/engineering_hydrology/double-ring-advantages
- Whole chapter: https://www.bctengineer.com/md/semester_5/engineering_hydrology/chapter-3

## Question

What are the advantages of double ring infiltrometer over single ring infiltrometer?

## Short answer

The outer ring prevents lateral spread, forcing vertical infiltration beneath the inner ring. This yields more accurate and reliable infiltration capacity values with one-dimensional flow, especially in permeable soils.

## Answer

A **double ring infiltrometer** has two concentric rings (inner about 30 cm, outer about 60 cm) driven into the soil, with both kept filled to the same water depth. Only the water added to the inner ring is measured.

**Advantages over a single ring infiltrometer**

1. **Reduces lateral spreading:** water in the outer ring (buffer) forces the water in the inner ring to infiltrate vertically downward, so the rate measured is true vertical infiltration. In a single ring, water spreads sideways under the ring and gives a value that is too high.
2. **More accurate and reliable values** of the infiltration capacity and the constant final rate $f_c$.
3. **Better field representation** because the flow beneath the inner ring is one-dimensional.
4. **Repeatable results:** the effect of soil non-uniformity near the ring edge is reduced, so tests at different sites are comparable.
5. **Usable on all soil types**, including very permeable soils where a single ring would show strong lateral flow.

Its disadvantages are that it needs more water and more labour than a single ring, and that driving the rings can disturb the soil.

## Check yourself

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

1. What is the main advantage of the double ring over the single ring?
   A. It is easier to drive into soil
   B. It uses less water
   C. Water in the outer ring forces inner ring water to go vertically, reducing lateral spreading
   D. It measures runoff
   Answer: C. The buffer ring ensures one-dimensional vertical flow below the inner ring. (Key point: Lateral spreading)

2. Why does a single ring give too high a value?
   A. Soil is compacted
   B. It is too large
   C. Evaporation is high
   D. Water spreads sideways under the ring
   Answer: D. Lateral spread adds extra infiltration that the measured vertical area does not account for. (Key point: Single ring error)

3. Which water is measured in a double ring test?
   A. Only the outer ring
   B. Only that added to the inner ring
   C. Evaporated water
   D. Total of both rings
   Answer: B. Both rings are kept at the same depth but only the inner ring's volume is recorded. (Key point: What is measured)

4. Which is a disadvantage of the double ring?
   A. It needs more water and labour
   B. It cannot be used in permeable soil
   C. It is less accurate
   D. It gives lateral flow
   Answer: A. Two rings need more water and effort, and driving them may disturb the soil. (Key point: Disadvantage)

## Related in Engineering Hydrology

- [Double ring infiltrometer, phi-index versus W-index](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Adouble-ring-phi-vs-w-index) — Engineering Hydrology, chapter 3
- [Horton constants from double ring infiltrometer data](https://www.bctengineer.com/question.md?key=semester_5%2Fengineering_hydrology%3Ahorton-constants-double-ring-data) — Engineering Hydrology, chapter 3

## Related in other subjects

- [Order of Newton's ring with double diameter](https://www.bctengineer.com/question.md?key=semester_1%2Fengineering_physics%3Anewton-ring-double-diameter-order) — Engineering Physics, chapter 4
- [Single, double, multiple timber roofs; king post truss](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Atimber-roofs-king-post) — Building Technology, chapter 4, asked 2×
- [Single and double handshaking](https://www.bctengineer.com/question.md?key=semester_4%2Fmicroprocessor%3Ahandshaking-single-double) — Microprocessor, chapter 4
- [Single vs double earth wire selection](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Asingle-double-earth-wire-criteria) — Transmission and Distribution System Design, chapter 3