Even well-designed drinking water wells can gradually lose yield as deposits build up in the filter zone and gravel pack. In the Karlsruhe region, detailed monitoring revealed processes that reduce performance, such as ochre formation driven by iron and manganese bacteria. This is often caused by mixing oxygenated, near-surface groundwater with deeper, oxygen-poor water during high-rate operation. For operators, this means increased pumping effort and energy consumption, as well as the need for timely, well-planned rehabilitation.
Stadtwerke Karlsruhe operates a large portfolio of wells (64 across four waterworks) and relies on precise documentation to identify the effects of ageing early on. The rehabilitation campaign described in the report focused on ten drinking-water wells with different constructions and screen types, including stoneware and Johnson-type filter screens (plus a bridge slotted screen). Some of these wells date back several decades and have large diameters and multiple filter sections — conditions that demand robust equipment and experienced execution during rehabilitation.
For the 2015 campaign, the High Pressure Impulse (HPI) process, which uses high water pressure in line with DVGW W 130, was selected. The key innovation tested was the MAXINOZ® nozzle rotation unit with adjustable angles, which allows the impulse direction to be adapted to the geometry of the screen material — unlike conventional systems, which generate impulses at a fixed 90° angle. In practice, rehabilitation pressures ranged from approximately 280 to 400 bar, depending on the screen type. Pre-cleaning was performed at a lower pressure of up to around 200 bar to remove casing deposits before the impulse-effective range begins.
The JET Master® system works by combining high-pressure impulses, vacuum generation and controlled movement through the filter interval. Two counter-rotating nozzle pairs create negative pressure zones that draw in loosened solids while impulses mobilise deposits in the gravel pack, ensuring even energy distribution across the borehole area. Continuous pumping throughout the process helps to keep the filter section active and facilitates the discharge of particles that reduce inflow, while regular solids measurements provide clear termination criteria and help to minimise downtime.
Documented before/after pumping tests show an exceptionally high average increase in specific yield of 152.5% across ten wells when using the JET Master® HPI process with the MAXINOZ® nozzle rotation unit. A differentiated view by screen material shows an average gain of around 143% for stoneware screens and approximately 179% for wells equipped with Johnson-type filters. For operators, this translates into tangible operational benefits, especially reduced energy demand due to a lower pump head after rehabilitation, alongside more reliable production capacity.
For more detailed information and the full report, please click on the PDF button.
Etschel Brunnenservice GmbH supports well operators by helping them to plan and execute professional well rehabilitation. If you have any questions regarding your well’s performance, please contact us for expert guidance.
