Every rehabilitation method does one of two jobs. It loosens what is plugging the screen and gravel pack, or it removes what has been loosened. Chemistry loosens. Brushes, swabs and jets loosen and stir. Pumping, airlifting and bailing remove. No single method does both jobs well, which is why the programs that work are combinations, and why a vendor selling one method is selling half a job.
This note goes method by method: what each does physically, what it is for, what it can damage, and what has to follow it. When to rehabilitate is covered in when to rehabilitate a water well; what it costs is in the line-by-line cost note.
Diagnose before you choose
The chemistry has to match the deposit, and the deposit has to be identified, not guessed. Three things identify it:
- A video survey of the casing and screen. Hard mineral scale, soft slimy biofilm, fines packed into the slots and a corroded or collapsed screen all look different, and the last one rules out most treatments.
- Water chemistry. Iron and manganese, pH, hardness and a bacteria test. The U.S. Army Corps of Engineers’ well maintenance guide singles out the ratio of dissolved to oxidized iron as one of the most useful indicators of iron fouling.
- A step test at known rates, so the result can be measured afterward against the same rates. How to read one is in step-drawdown or constant-rate test.
And one question the diagnosis has to answer first: is it the well at all? A pump that has worn or an aquifer that has dropped will not respond to any of what follows. How to tell which.
Mechanical methods
| Method | What it does | Watch for |
|---|---|---|
| Brushing | Scrubs deposits off the casing and screen face | Wire can cut soft or corroded steel; nylon is gentler. Not for plastic |
| Swabbing and surging | A tight-fitting block, pulled up and down, forces water in and out of the screen and pack | Can collapse weak or plastic screen. The block must match the screen’s inside diameter |
| Airlifting | Compressed air lifts water and loosened material out of the well | Needs enough water above the air line to work |
| Jetting | High-velocity water from rotating nozzles, level by level through the screen | Dirty water jetted at pressure acts like a sand blaster on the slots; it can also drive fines deeper into the pack |
| Dual-swab airlift | Two swabs isolate a short interval of screen while an airlift pulls water out of just that interval | Slow and hour-priced, but it cleans one zone at a time instead of the path of least resistance |
The Corps guide gives working numbers for jetting: nozzle velocity of at least 150 feet per second, the tool turned slowly, a couple of minutes at each level, and the well pumped at slightly more than the jetted flow so that material comes out rather than going in. The last condition is the one that separates cleaning from damage.
Chemical methods
Acids, for mineral scale
Acids dissolve carbonate scale and iron and manganese deposits. They do little to biofilm on their own. Agriculture and Agri-Food Canada’s guidance rates the common acids like this:
| Acid | Carbonate scale | Iron and manganese | Biofilm |
|---|---|---|---|
| Hydrochloric | Very good | Very good | Poor |
| Sulfamic | Very good | Fair | Poor |
| Phosphoric | Very good | Good | Poor |
| Hydroxyacetic | Poor to fair | Good | Moderately good |
The practice points that recur across the sources:
- Keep the pH down. Guidance ranges from below 2 to no higher than 3 during treatment; once the pH rises, dissolved iron drops back out as a fresh deposit.
- Mind the contact time. From a few hours to more than fifteen, but shorter where the formation holds clays that swell.
- Mind the metal. Use an inhibitor with metal screens. The Corps guide cautions that hydrochloric acid is harmful to stainless steel, and phosphoric acid leaves phosphate behind, which is food for bacteria.
Chlorine and other oxidizers, for biofouling
Iron-related bacteria build a slime that traps iron and fines. Chlorine at rehabilitation strength (published guidance runs from about 500 to 2,000 mg/L, held for a day or more) attacks the biofilm; acid does not. Two cautions matter. First, pH: chlorine is a much weaker biocide in alkaline water, so the water is often brought down toward pH 6 first. Second, strength: a 2025 Water Well Journal review notes that extreme chlorine concentrations did more harm than good, attacking soft metals and rubber.
Dispersants, for clays and fines
Dispersants keep clay particles from sticking so they can be pumped out. The old choice, polyphosphate, is now discouraged. The Corps guide recommends against it for maintenance treatment, and a 2023 Water Well Journal article notes that phosphate is food for bacteria and can leave a glassy coating. Non-phosphate dispersants are the usual substitute.
Rules that are not optional
- Never mix acid and chlorine, in the well or in a tank. The result is chlorine gas.
- Neutralize at the surface, never in the well. Spent acid is pumped to tanks and neutralized there.
- Use chemicals certified for drinking water. California requires additives to drinking water to be certified to NSF/ANSI 60.
Impulse and energetic methods
These methods send a pressure pulse through the water column and into the pack. They are sold under brand names; the families are:
- Pneumatic impulse. Compressed gas released in bursts inside the screen. Tools marketed as AirBurst and BoreBlast work this way; a federal court opinion describes the latter as a compressed-gas tool fired through a relief valve.
- Detonating cord. Small explosive charges fired in a timed sequence. A 2025 Water Well Journal article describes Sonar-Jet as using a detonating cord and warns that this family can harm older or fragile wells.
- Electro-hydraulic. An electrical discharge in the water makes the pulse. The only material we found on it is the vendor’s own.
- Carbon dioxide injection. Gaseous and then liquid CO2, which forms carbonic acid and expands rapidly as it turns to gas, followed by surging and airlifting. A 2024 peer-reviewed field paper describes injection pressures of 40 to 450 psi and flushing until pH and CO2 return to background.
The honest summary of the evidence: independent, peer-reviewed results are thin, and the large percentage improvements in circulation come mostly from the companies selling the method. One peer-reviewed single-well study of a sonic method found a 25 to 55% improvement. Every one of these methods still needs a removal step afterward, and every one is a risk to casing and screen that is already thin. The video comes first.
Why combinations work
The sources agree more on this point than on any other. The Corps guide says chemical treatments are far more effective with mechanical mixing and development. The National Ground Water Association’s well-owner guidance says to agitate the chemicals frequently for 24 to 72 hours. A chemical left to sit in a well dissolves the deposit it touches and not much else.
A typical sequence for a plugged municipal well therefore looks like this: brush, then bail or airlift what the brush loosened; video; chemical treatment matched to the deposit, agitated by swabbing; remove and neutralize at the surface; dual-swab airlift zone by zone until the water runs clear; repeat the chemistry if the first pass was not enough; disinfect; video and test.
| Method | What it removes | Main risk | What must follow |
|---|---|---|---|
| Brushing | Deposits on the screen face | Soft or corroded steel | Bailing or airlift |
| Swabbing | Fines; mixes chemicals | Collapse of weak or plastic screen | Airlift or pumping |
| Jetting | Plugging in screen and pack | Slot erosion; fines driven inward | Pumping at more than the jetted flow |
| Acid | Carbonate and iron scale | Metal attack; gas if mixed with chlorine | Surface neutralization |
| Chlorine | Biofilm | Weak at high pH; rubber and soft metal | Dechlorination; bacteria tests |
| Polyphosphate | Clays | Feeds bacteria | Better avoided |
| Impulse | Plugging in pack and screen | Weak casing | Airlift or swabbing |
Proving it worked
A rehabilitation is proved by numbers, not by how clean the video looks:
- A step test before and after, at the same rates. The change in well loss is the measured result of the work. The Corps guide calls the step-drawdown test probably the most valuable hydraulic testing tool available for this.
- A video before and after, so the screen’s condition is on record, not just its output.
- A wire-to-water test when the pump goes back in, so the pump’s share of any change is separated from the well’s.
- Disinfection and bacteriological sampling before the well returns to service, as California’s drinking water rules require for a repaired well.
What to do with this on Monday
- Before scoping any rehabilitation, pull the well’s water chemistry and latest video. If neither exists, that is the first line item.
- Write the method as a sequence, loosen then remove, with the removal steps named and quantified, not “chemical treatment as needed.”
- Put the chemical rules in the specification: certified products, no mixing, surface neutralization, a named disposal route.
- Ask for the evidence behind any impulse method: independent results on wells like yours, and what happens to a screen in the condition your video shows.
- Make the before-and-after step test a pay item, at rates written into the contract.
Quick answers
What is the best method to rehabilitate a water well?
There is no single best method. The treatment has to match the deposit (acid for mineral scale, chlorine for biofouling, dispersant for clays), and it only works when combined with mechanical agitation and thorough removal by swabbing, airlifting or pumping.
Can you use acid and chlorine together in a well?
Not at the same time. Mixing acid and chlorine releases chlorine gas. Programs that use both run them as separate steps, with the acid removed and neutralized at the surface before the chlorine goes in.
How do you know if a well rehabilitation worked?
Run a step test at the same rates before and after, and compare the drawdown at each rate. A video survey before and after documents the screen, and a wire-to-water test on the reinstalled pump separates the pump’s condition from the well’s.
See every treatment on your wells next to the step tests before and after it. Request a walkthrough →
Sources
- U.S. Army Corps of Engineers. EP 1110-1-27, Operation and Maintenance of Extraction and Injection Wells at HTRW Sites. 2000. Source for jetting practice, acid pH and contact time, the stainless steel and phosphoric acid cautions, the recommendation against polyphosphates, surface neutralization, iron ratio as an indicator, mechanical mixing with chemicals, and the step-drawdown test as the key measure.
- Agriculture and Agri-Food Canada. Well rehabilitation. Source for the acid effectiveness ratings.
- Schnieders, M. Mechanical Well Rehabilitation and Well Rehabilitation Done Right. Water Well Journal, 2020. Source for brush materials, jetting driving material into the pack, and combined chemical and mechanical programs.
- Schnieders. Chemical Usage in Well Rehabilitation. Water Well Journal, 2017. Source for acid dosing ranges and inhibitor practice.
- Butts, E. Well Development and Rehabilitation Methods. Water Well Journal, 2025. Source for the detonating-cord description, its risk to fragile wells, and the harm from extreme chlorine concentrations.
- Hanna. The Well Development Process. Water Well Journal, 2023. Source for swab sizing, collapse risk in plastic screen and polyphosphate drawbacks.
- Schofield. Chemical Well Rehabilitation. Water Well Journal, 2025. Source for pH adjustment before chlorination.
- Penn State Extension. Water Well Maintenance and Rehabilitation. 2025. Source for rehabilitation-strength chlorine ranges and the warning against mixing acid and chlorine.
- National Ground Water Association. Restoring flow. Source for agitating chemicals for 24 to 72 hours and identifying the clog before choosing chemicals.
- California Code of Regulations. Title 22, section 64590. Source for NSF/ANSI 60 certification of drinking water additives.
- California Code of Regulations. Title 22, section 64583. Source for bacteriological sampling of a repaired well before use.
- Frazier v. Layne Christensen Co., 370 F. Supp. 2d 823 (W.D. Wis. 2005). Source for the description of a compressed-gas impulse tool.
- Kahuda et al. Coatings 11:1250. 2021. Source for the single-well sonic study result.
- Patil et al. Scientific Reports 14:13838. 2024. Source for CO2 injection pressures and post-treatment flushing.
Every link above was retrieved and read on 2026-09-26. Paid standards are named by designation so you can check them against your own copy.