HydraSleeve vs. Bailers

HydraSleeve Bailer


  • A 2-inch empty HydraSleeve, including the weight, only displaces ~75 ml. Its shape is streamlined, similar to a ribbon with weight attached to the bottom.
  • Dye studies show minimal disturbance to the water column during HydraSleeve placement
  • The HS is flat, empty and sealed shut during placement.
  • A disposable bailer that fits 2-inch wells displaces 1000 ml, over 10 times as much as a HydraSleeve.
  • Dye studies show considerable mixing and drag-down of fluid in the water column during placement of a bailer.
  • The interior of the bailer is open during placement. Extraneous, stagnant fluid from the casing flows into the bailer is carried down as the bailer descends. This is true for both single and double check valve bailers.

Well Equilibration

  • Underwater, the HydraSleeve can remain flat and sealed for indefinite time periods. It will not open until activated by pulling upward for sample collection.
  • When a bailer is left in water column it is closed on the bottom by the check valve and open on the top. A column of stagnant water forms inside the rigid bailer during the well equilibration period.

Sample Collection

  • When activated, the HydraSleeve collects a sample from a very defined interval in the well with minimal agitation and no displacement. When full it seals itself, isolating the sample from fluid from other zones. HydraSleeve provides a simple method for collecting a water sample from a defined vertical and horizontal interval within the well.

  • Dye studies show that bailers, including dual check valve bailers, will not retain a sample from a specified interval. Any change in recovery speed results in the momentum of the sample in the bailer to continue upward and out the top of the bailer. Simultaneously, water enters the bottom of the bailer to replace the water exiting the top. In short, the bailer continuously pumps itself during recovery (picture a very short inertial lift pump). Only when the top of the bailer clears the water table does the sample become “heavy” enough to seat the bottom check valve, sealing the fluid in the bailer as it is recovered through the air in the casing.

Sample Discharge

  • The pointed discharge tube and flexible HydraSleeve body allows discharge flow rates to be easily controlled. The flexible sleeve collapses as sample is withdrawn, preventing air from contacting the sample in the HydraSleeve.
  • Bailers usually require a bottom discharge device to control the sample flow rate. As water is drained from a bailer it is replaced by air, which comes into direct contact with the sample. If the sample is poured from the top of a bailer an air bubble travels up and down the length of the bailer as the sample is discharged.


  • HydraSleeves are flexible and light. Large volumes of HydraSleeves can be shipped in small, lightweight parcels.
  • Bailers occupy a larger volume and weigh more than HydraSleeves, resulting in higher shipping costs.


  • Used HydraSleeves can be easily rolled or compressed to minimize disposal volume.

  • Rigid bailers occupy a larger, fixed volume and are more difficult to compress for disposal.