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Waterra Well Slug for aquifer characterization

A Waterra Well Slug helps characterize your aquifer permeability

The Waterra Well Slug is a convenient, fixed volume, cylindrical solid for performing instantaneous, rising or falling, head permeability tests (hydraulic conductivity) in boreholes.

The Waterra Well Slug (WWS-2X3) is designed specifically for 2″ Schedule 40 monitoring wells, but in practice can be used in larger monitoring well. It consists of three sections (and is sold as a 3 section assembly) of solid Acetal Rod which can be used either individually or together to produce greater displacement.

It is constructed of Acetal (Delrin) thermoplastic because of its long acceptance as a material of choice for groundwater monitoring equipment. It is known for its durability, its chemical resilience in harsh environments, and unlike some polymers, acetal thermoplastic is PFOA and PFAS free.


  • Constructed in three segments for flexible use and easy transportation
  • Durable, long lasting, chemically resistant material of construction
  • Easy to use


Individual Section of the Waterra Well Slug
Length1.63' (497.4 mm)
Diameter1-5/8" (41.28 mm)
Volume0.15 imp gal (0.18 US gal) (0.67 L)
Three Sections of the Waterra Well Slug
Length4.9' (1492 mm)
Diameter1-5/8" (41.28 mm)
Volume0.44 imp gal (0.53 US gal) (2.0 L)
Waterra Well slug showing 3 sections and assembled slug

Let’s get started...

Waterra Words of Wisdom

  • Permeability (Hydraulic Conductivity) tests help understand aquifers
  • The test is simple, quick and requires a minimum of equipment
  • Waterra Well Slugs are made of Acetal (Delrin) which is a tough thermoplastic
  • Acetal / Delrin does not contain PFOAs or PFAS
  • Call us or our distributors if you need help
  • We have graduated tape as an accessory below that you may find useful.

Variable Head Permeability Tests

One of the oldest methods of calculating a formation’s permeability (hydraulic conductivity) is to use a simple tool known as well slug.

The slug is a solid object of a known volume and displacement, which can be quickly immersed or withdrawn from a water column. This produces near instantaneous head level changes in a well. Values for permeability can be calculated with the use of a slug, a stopwatch, and a water level indicator.

Today many people use a pressure transducer and data logger which will produce more precise data; often taking readings in ¼ second intervals.

There are two approaches; a Falling Slug Test and a Rising Head Test as illustrated below.

Waterra Well Slug Rising & Falling Head Tests

Rising Head Test                        Falling Head Test

2" Schedule 40 PVC (2.069" ID) Volumes & Displacements

Linear Volume Per Unit Length
1 Foot0.145 Imp. Gal. / 0.174 US gal.
1 Meter2.169 Litre
Slug Displacements With WWS-2X3
No. of SectionsDisplacement
112.1" (307 mm)
336.3" (922 mm)
Technical Paper:
Pumping and Slug Tests
State of Ohio EPA

Waterra Graduated Tether

Waterra Graduated Tether
Length3000 feet (914 m)
Width3/16" (4.8 mm)
Markingsgraduated in feet from 0' to 3000' with markings at one foot increments
Materialwaterproof polyester
Average Breaking Strength170 lbs (0.756 kN)
Volume0.44 imp gal (0.53 US gal) (2.0 L)
Waterra Graduated Cord
Purchase Graduated Tether

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