Declining well yields are often linked to clogging of the filter slots, filter gravel and the area surrounding the well. In groundwater containing iron and manganese, the precipitation of oxides and hydroxides can begin inside the well itself, driven by changes in flow velocity, temperature and oxygen contact during pumping. This process can be accelerated by harmless, naturally occurring bacteria that metabolise these compounds. The case study in the PDF is based on a well in the “Moos bei Plattling” field. Constructed in 2000, it has a DN750 stainless steel winding-wire screen and a ~4 m filter section. Heavy deposits were observed, as well as a drop in performance and temporary sand production. Earlier rehabilitation attempts using a nozzle system that rotated in one plane combined with gas compression impulses did not achieve the desired outcome.
The well was rehabilitated using the High Pressure Impulse Process® with high water pressure (HPI) via the JET Master® system from Etschel Brunnenservice GmbH. A high-pressure pump drives water through nozzles at up to 550 bar; an eccentric arrangement creates recoil-driven rotation at approximately 7,000 rpm. Rather than a sustained, directed jet hitting the well lining, the rotating jets convert energy into pressure-wave impulses upon contact with the well water. These impulses propagate through the screen, extension piping and filter gravel into the formation, generating vibrations that loosen deposits — even hardened encrustations — while continuous pumping removes the mobilised material. The PDF emphasises that the operator must adjust parameters such as pressure, driving speed, nozzle distance, nozzle type and jet angle to match the lining material and structural condition, in order to achieve effective depth without causing damage.
As part of practical field tests, the newly designed and patented MAXINOZ® double rotation unit was used. This unit features two pairs of nozzles that rotate in opposite directions in two planes. Compared with the UNINOZ® unit, which has been in use since 1991, the MAXINOZ® unit also allows the outlet angle to be adapted to the specific geometry of the well lining. In practice, this results in more controlled impulse distribution and better compatibility with different lining materials. Camera inspections documented extensive iron and manganese oxide precipitates in the filter area before rehabilitation, and showed free filter slots after completion (see the before-and-after images in the PDF).
During rehabilitation, the JET Master® discharged a total of 389 litres of fine sand and 11,602 litres of finer components (‘sludge’) at a water flow rate of 545 m³, reaching the termination criterion after two hours. Measurement was performed via extraction from the pump flow, with evaluation using Imhoff hoppers (see the PDF for the discharge diagram and measurement images). The pumping rate was adjusted from 50 l/s to 80 l/s once the removal of finer components began, and this higher rate coincided with a marked increase in fine sand discharge, supporting the ‘desanding effect’ described for this method. Pumping tests performed before and after rehabilitation demonstrate a significant increase in specific yield: at 30 l/s, specific yield increased from 20.3 to 66.7 l/s per metre (+229%), and at 40 l/s, it increased from 17.2 to 51.9 l/s per metre (+201%).
This case study reinforces a key message from the PDF: modern, chemical-free rehabilitation can restore a well’s “true” capacity, even many years after construction. This can effectively complete the development process that the original method did not fully achieve. Improved yields can lower operating costs and energy demand, potentially reducing the number of wells required to meet supply needs. For water suppliers and operators, combining documented inspection, controlled impulse-based cleaning and verifiable pump-test data is key to confirming results.
For more detailed information, please click on the PDF button to access the full technical field report and figures.
Etschel Brunnenservice GmbH supports well operators with inspections, rehabilitation and performance optimisation. If you have any questions about your well’s condition or would like to discuss a rehabilitation approach, please contact us for expert guidance.
