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Solid H(o) Slug ®
By Midwest GeoSciences Group

(click to enlarge)

H(o) Slug Video
Solid H(o) Slug Video

Download the
Solid H(o) Slug Information PDF

Guidelines for Improving the
Quality of Slug Tests

(from Butler, McElwee and Liu, 1996,
see link below)

  • Three or more slug tests per well
  • Two or more Initial Displacements (H(o))
  • Near-Instantaneous H(o)
  • Appropriate data-acquisition equipment
  • If storage parameter is needed, sufficient high-quality data is required
  • Appropriate analytical solution and software
  • Pre- and Post- Analysis Plots
  • Consideration of subsurface conditions and well configuration

Professional Paper:
Butler, McElwee and Liu, NGWA, 1996

Pronounced: H naught slug


The Solid H(o) Slug ® by Midwest GeoSciences Group is a traditional solid slug for slug testing. It is designed to yield a pre-estimated initial displacement in two-inch diameter wells for improving confidence and accuracy of slug testing.

Knowing your expected initial displacement BEFORE the slug test allows you to recognize problems, noise or technical difficulties DURING the test...and the allows you to correct your slug test for better results.

It's a new item available only through Midwest GeoSciences Group. You can choose between imperial or metric initial displacements to match your data collection methods and it's available now for common initial displacement lengths H(o)*:

Imperial UnitsMetric Units
12 inch displacement30 centimeter displacement
18 inch displacement45 centimeter displacement
24 inch displacement60 centimeter displacement

Three slug tests using at least two initial displacements are found to be best-practice standards and recommended by Jim Butler's book: The Design, Performance and Analysis of Slug Tests (see below) which has become the standard reference for slug testing around the world. Three initial displacements allow a measure of test performance and an estimation of the noise to data ratio during normalization of the data during analysis.

Engineered Design

The Solid H(o) Slug is specifically designed with tapered ends exceeding an 80 degree angle to reduce the pressure wave that can occur with other solid slugs leading to noisy data and reducing the reliabilty of test data.

Calculated initial displacement is represented by "H(o)*" where H is the calculated distance of instanteous change at time zero (o) in water level created by the the slug. "H(o)" is the measured initial displacement. It is important to compare calculated H(o)* with measured H(o) as part of the QA/QC of the slug test for checking the reliability of test data.

PVC Version:
Solid H(o) Slug ®

Imperial or Metric Units
3 Slugs:$147.00($49 each)
2 Slugs:$128.00($64 each)
1 Slug:$89.00

  Please Check the "Initial Displacement H(o)" that you prefer:


Performing slug tests with the Midwest GeoSciences Group solid H(o) slugs are perfect for determining K-values efficiently. In my experience, H(o) values tend to fit better at well locations with low K values, however data is also reliable and accurate for wells with high K values. They are straight forward and easy to use.
- Christian Bruchman, Arcadis



The Pneumatic Hi-K Slug™ by Midwest GeoSciences Group is the answer for accurate rising head tests in fast recovery wells!

90-min WEBINAR:

Practical Guidelines to Improve Efficiency and Accuracy

by: Jim Butler, PhD.

The Design, Performance and Analysis
of Slug Tests, Second Edition

By Jim Butler, PhD, (CRC Press, 2020)

Download a free Demo Version or learn more about ordering the analysis software, AQTESOLV, used by more hydrogeologists than any other software.

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