Ask three districts when they rehabilitate a well and you get three answers: on a fixed cycle, when a pump comes out for other reasons, or when the well can no longer meet demand. All three are guesses. The decision has a right answer for each well, and it is an economic one: the moment the cost of waiting another year exceeds the cost of treating now.
Know which kind of decline you have
Rehabilitation only helps the part of the decline that lives in the well — the screen, the gravel pack and the near-well formation. Before scheduling it, separate the signals: the specific capacity trend for plugging, the static level trend for the aquifer, the wire-to-water efficiency trend for the pump. A well whose specific capacity has held but whose efficiency has fallen needs a pump rebuild, not a chemical treatment. A video survey resolves the rest: encrustation looks different from biofilm, and both look different from a collapsed screen.
Methods, matched to the fouling
| Fouling | What works | What to avoid |
|---|---|---|
| Carbonate and iron/manganese mineral scale | Acidization with an inhibited acid, followed by mechanical agitation (brushing, surging, jetting) and thorough development pumping | Acid without agitation — the scale softens and stays put |
| Biofouling (iron-related bacteria) | Shock chlorination or a biocide with a dispersant, then mechanical removal and development; sometimes repeated | A single chlorine dose with no mechanical step — regrowth in months |
| Silt, sand and clay in the pack | Dispersant (polyphosphate) and energetic development — surging, airlifting, jetting; pressure-pulse or gas-impulse tools where the casing condition allows | Over-pumping to ‘clear it out’, which pulls more fines |
| Screen corrosion or collapse | Liner, screen replacement or a new well | Any chemical treatment |
Why earlier is cheaper
Mineral scale that has been in place for years mineralizes and bonds to the screen; a treatment that would have restored 90% of the original specific capacity in year three restores 60% in year six, and the next cycle starts from a lower baseline. Meanwhile the deeper pumping level raises energy cost every day (each additional foot of lift on a 900 gpm well at $0.18/kWh is roughly $250–350 a year at typical run hours), the pump drifts off its curve, and peak-season capacity quietly shrinks. Districts that treat at a 15–25% decline in specific capacity typically see three outcomes: better recovery, longer intervals between treatments, and a rehabilitation bill that the energy savings alone repay.
A worked decision
A 1,000 gpm well has fallen from 22 to 17 gpm/ft — a 23% decline. The extra 14 ft of drawdown costs about $3,500 a year in energy at $0.18/kWh. A brushing-and-acid program with a post-treatment test is quoted at $45,000 and, on this well’s history, recovers 85% of the loss. Waiting two more years at the observed rate takes the decline past 40%, where recovery on similar wells in the district has averaged 55%, and the energy penalty compounds. The numbers say treat now. The Markov lifecycle model in Waterwell IQ makes this comparison for every well every month, using the district’s own transition history rather than a generic rule.
What to record
A rehabilitation is only as useful as its record: the pre-treatment step test and video, the chemicals and quantities, the mechanical steps, the development pumping log, the post-treatment test at the same rate, and the itemized cost. That record is what tells you, five years on, whether the same program is worth repeating. Waterwell IQ’s rehabilitation template captures all of it, including an itemized cost breakdown, and the AI reads a contractor’s own report into the same structure.
See where your wells sit on the lifecycle model, with a probability on each rehabilitation window. Request a walkthrough →
Sources
- Water Well Journal (National Ground Water Association). Well Development and Rehabilitation Methods, Ed Butts, PE, CPI. 2025.
- National Ground Water Association. Water Well Rehabilitation: Private Wells and Public Water Systems. 2016.
- Water Replenishment District of Southern California. Specific Capacity — A Measure of Well Performance, Well Problems, and Aquifer Transmissivity, Technical Bulletin TB02 (Part 1 of 2). 2005. Source for specific capacity as gpm per foot of drawdown, its decline as perforations and filter pack plug, and the 25% decline commonly used as a rehabilitation trigger.
Every link above was retrieved and read on 2026-09-09. Paid standards are named by designation so you can check them against your own copy.