A green pool is alarming and unmistakable. One day the water is clear, the next you cannot see the bottom and the surface has the unmistakable green tint of an algae bloom. The good news: almost every green pool can be cleared without draining, often within a few days, when you follow the right process in the right order.
A green pool is alarming and unmistakable. One day the water is clear, the next you cannot see the bottom and the surface has the unmistakable green tint of an algae bloom. The good news: almost every green pool can be cleared without draining, often within a few days, when you follow the right process in the right order.
This guide is the complete WETYR Pools reference on green pool recovery. We have run green-to-clean recoveries on hundreds of pools across the United States, including pools that were so neglected the surface looked like a swamp. The process below is what works, in the order it has to be done.
If your pool is severely green or has been green for weeks, request a professional green-to-clean visit from WETYR Pools. We can usually have a pool clear within a few days even in extreme cases. Use the form on this page or email [email protected].
A green pool is an algae bloom. Algae spores are present in every pool environment; they bloom when sanitizer levels drop and conditions favor growth. Heat, sunlight, rain that dilutes chemistry, a failed pump, a clogged filter, a vacation without service, or simply running too low on chlorine all trigger blooms.
There are three common algae types. Green algae is the most common and the easiest to clear; it appears as a green tint or floating mats. Yellow or mustard algae looks like sand or pollen settled on walls and floor and is much more resistant to chlorine. Black algae appears as dark spots or patches that root into plaster and is the most stubborn of all.
Identifying the algae type matters because the treatment differs. The process below addresses green algae. Mustard and black algae require specialized algaecides and more aggressive brushing and shocking.
Severity affects how long recovery takes and how much chlorine you need.
Light green (you can still see the bottom): a one-shock recovery, usually clear within 48 hours. Cloudy green (bottom is faintly visible): two shocks needed, three to five days. Opaque green (cannot see anything below the surface): may need three shocks plus floc, five to seven days. Swamp green (with visible debris, mats, mosquitoes): requires draining or professional green-to-clean recovery; a week or more.
If your pool is at the swamp level, do not try to chlorinate your way out of it. The chlorine demand is essentially infinite at that point. Request a WETYR Pools green-to-clean visit; we drain and clean to the level appropriate to the pool's age and finish, then refill and rebalance.
Before you start, gather: a water test kit (drop kit, test strips, or a Taylor K-2006 reagent kit are reliable), pH up and pH down chemicals, calcium hypochlorite shock (also called cal hypo or dichlor) sized for your pool volume, a sturdy pool brush, a manual vacuum or a robotic cleaner, a clarifier or flocculant for severe cases, and a clean filter (cartridge filters often need replacement or deep cleaning before shocking).
Run the pump 24 hours a day during recovery; expect higher electricity cost during the few days of recovery. A working pump, a working skimmer, and a working filter are prerequisites; if any of those are broken, fix them first or the recovery will not work no matter how much chemistry you add.
Test pH, total alkalinity, free chlorine, total chlorine, calcium hardness, and cyanuric acid (stabilizer). Record everything. The numbers tell you what to fix in what order. Total chlorine high but free chlorine low means combined chlorine (chloramines); a heavy shock will clear those. Cyanuric acid extremely high (over 100 ppm) blunts chlorine effectiveness; partial drain may be required.
Brush the walls, floor, steps, and corners thoroughly with a stiff pool brush. Brushing disrupts the algae bloom, exposes cells to chlorine, and is essential to recovery. Brush again before each shock dose. Algae that hides in corners or under ledges will keep blooming if you do not break it loose.
A dirty filter cannot capture the dead algae that shocking produces. Backwash a sand or DE filter, or take a cartridge filter apart and clean it (replace cartridges that are at end of life). Run the filter while you do everything else. The filter is what will carry the algae out of the water; if it is clogged, recovery stalls.
Chlorine is dramatically less effective at high pH (above 7.8) and can degrade liner finishes at low pH (below 7.2). Adjust pH to between 7.2 and 7.4 before shocking. Total alkalinity should be 80 to 120 ppm. Skipping this step is the most common reason home shock attempts fail; chlorine added to high-pH water sanitizes poorly and burns off quickly.
Add a heavy dose of cal hypo, dichlor, or liquid chlorine. The standard recommendation for green algae is to triple-shock: about 3 pounds of cal hypo per 10,000 gallons (read the product label for your specific product). Pour around the perimeter with the pump running. Always add chlorine to water, not water to chlorine. Shock at dusk or after sunset; sunlight burns off chlorine fast and undercuts the shock.
Filtration is what removes the dead algae after chlorine kills it. Run the pump continuously, day and night, until the water clears. Backwash or clean the filter daily during recovery; it will clog quickly. If the filter pressure rises 8 to 10 psi above clean baseline, stop and clean before continuing.
After 24 hours, test the water. If chlorine is still high and the water is turning blue-green or cloudy white, the algae is dying. Brush again. If chlorine has dropped below 5 ppm and the water is still green, the chlorine demand was higher than the first shock; re-shock with another full dose. Repeat until the chlorine holds at 5+ ppm and the water turns clear, cloudy, then transparent.
Dead algae settles to the floor as a fine cloud of debris. Manually vacuum to waste (skipping the filter) if your filter has a multiport valve and the level allows. Alternatively, use floc to drop the debris to the floor overnight, then vacuum. Robotic cleaners can handle modest amounts but will overload their cartridges in heavy recovery.
Once the water is clear, test and re-balance pH, alkalinity, calcium hardness, and cyanuric acid. Bring chlorine to a normal maintenance level (1 to 3 ppm). Add a maintenance dose of algaecide as a preventive (some homeowners do, some do not; it is optional if chemistry is disciplined). Resume normal weekly service.
Light and cloudy green pools recover reliably with the home process above, assuming the pump, filter, and skimmer are all functional. The chemistry is straightforward and the chlorine demand is finite.
DIY recovery fails when the pool is swamp-level, when the equipment is not working, when the pool has been green for weeks with built-up debris and biological mass, when the homeowner cannot run the filter 24/7 (a vacation rental, an absent owner), or when the cyanuric acid is so high that chlorine is functionally inactive.
In any of those situations, the right call is professional green-to-clean. WETYR Pools handles green-to-clean recoveries across the United States as part of our pool maintenance and service program. For severe cases we drain, acid wash if needed, clean the filter completely, and refill. The recovery takes a few days; the cost is usually significantly less than the cost of weeks of failed home attempts.
WETYR Pools provides green-to-clean service across our maintenance markets. A typical professional recovery follows the same steps as above but uses commercial-grade equipment, the right chemistry doses calculated to your specific pool, and an experienced eye on what each color and clarity change means in terms of next steps. For severe cases, drain-and-clean is faster and cheaper than chemical-only recovery.
Cost for professional green-to-clean ranges from about $300 for a simple chemistry recovery on a small clean pool, to $800 to $1,500 for a moderate recovery, to $1,500 to $5,000+ for a severe drain-and-clean job that includes filter media replacement, pump service, and refill. WETYR Pools quotes every green-to-clean job as a fixed itemized proposal after an assessment visit.
The same disciplined maintenance that prevents most pool problems prevents algae. Keep chlorine between 1 and 3 ppm at all times. Keep pH between 7.2 and 7.6 and total alkalinity 80 to 120 ppm. Run the pump enough hours each day to turn the water over at least once. Clean the filter on schedule. Brush the pool weekly. Test water at least weekly.
Pool covers, especially solar covers, dramatically reduce algae risk because they limit sunlight that drives photosynthesis. Salt chlorine generators produce a steady chlorine residual that resists blooms. Variable-speed pumps run longer hours at lower cost, which improves filtration without raising the electric bill. WETYR Pools' weekly service includes all of this routinely; for owners who maintain their own pool, the discipline above is what keeps water from going green.
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20 of the most-asked questions on Reddit, Quora, and pool owner forums, answered by the WETYR Pools team.
Your pool is green because of an algae bloom. Algae spores are always present; they bloom when chlorine drops, when pH is high (which weakens chlorine), when filtration is inadequate, or after a long absence without service. Heat and sunlight accelerate the bloom.
Light green: 24 to 48 hours with disciplined shocking and 24/7 filtration. Cloudy green: 3 to 5 days. Opaque green: 5 to 7 days. Swamp green: a week or more, often requiring drain-and-clean.
Standard guidance is to triple-shock for green algae: about 3 pounds of calcium hypochlorite per 10,000 gallons (read the specific product label). Re-shock if the chlorine demand is high. Always balance pH to 7.2 to 7.4 before shocking.
No. A green pool has high bacteria and unbalanced chemistry. Risks include ear infections, eye irritation, and gastrointestinal illness. Wait until the pool is fully clear and chemistry is balanced (chlorine 1 to 3 ppm, pH 7.2 to 7.6) before swimming.
Usually no. Most green pools clear with chemistry-only recovery. Drain-and-clean is needed only for swamp-level pools, pools with excessive cyanuric acid (over 100 ppm), or pools with heavy debris and biological mass. WETYR Pools assesses on visit.
Common causes are pH too high (chlorine ineffective), filter clogged or broken, cyanuric acid too high, mustard or black algae instead of green, or the shock dose was too small for the bloom size. Re-test, brush, clean the filter, and re-shock with a larger dose.
Green is the most common and clears with standard shocking. Mustard (yellow) algae looks like sand on walls and resists chlorine; treatment requires specialized algaecide and aggressive brushing. Black algae roots into plaster as dark spots; the most stubborn type, often requiring repeated treatment over weeks.
Indirectly, yes. The algae mass loads the filter heavily and can crack a clogged cartridge or push DE through grids. Pumps running with restricted flow may overheat. Always clean or replace filter media after green pool recovery.
Maintain free chlorine 1 to 3 ppm always, pH 7.2 to 7.6, run the pump enough hours per day for full turnover, brush weekly, clean the filter on schedule. A salt chlorine generator and a pool cover dramatically reduce risk. WETYR Pools weekly service handles all of it.
Chemistry-only professional recovery: $300 to $800. Recovery with floc or partial drain: $500 to $1,200. Full drain, acid wash, and refill on a severe case: $1,500 to $5,000+. WETYR Pools quotes after an assessment visit.
Yes. WETYR Pools provides green-to-clean recovery as part of our pool maintenance and service program across the United States. Request a visit through the form on this page or email [email protected].
The bucket test isolates evaporation from a leak. It is not used to diagnose green pool, which is a chemistry and biology problem. See our How to Stop a Pool Leak guide for the bucket test.
Rain dilutes chlorine and adds organic debris, which can trigger an algae bloom if chlorine was already marginal. Shock the pool after major storms as a preventive.
Maintenance algaecide is optional. If chemistry is consistently disciplined, you do not need it. It can help as a preventive in pools with recurring algae or as a treatment for mustard or black algae alongside shocking.
Algae itself does not damage plaster, but a green pool often signals that chemistry has been off, and unbalanced chemistry does erode finishes. Recovery uses higher-than-normal chlorine briefly; this does not damage plaster if pH stays in range. Acid washing during severe drain-and-clean does etch plaster slightly; it is a tradeoff in extreme cases.
Calcium hypochlorite shock runs about $5 to $10 per pound; dichlor is similar. A typical residential green pool recovery uses 5 to 15 pounds, so $25 to $150 in shock for DIY. Liquid chlorine is cheaper per pound but heavier to handle.
Salt chlorine generators reduce algae risk but do not eliminate it. The cell may be dirty or failing (clean or replace), the salt level may be low (test), or the generator output may be set too low. Shock the pool with regular chlorine (not by raising salt cell output), then diagnose the cell.
Yes, household bleach (6 to 8.25 percent sodium hypochlorite) is the same chemical as liquid pool chlorine. You need significantly more bleach than concentrated shock product for the same result, but it works. Check the percentage on the bottle.
Once a week to once every two weeks during the swim season, plus after storms, after heavy use, and any time combined chlorine builds up. Many salt pool owners do not regularly shock because the generator produces continuous chlorine.
We use calcium hypochlorite (cal hypo) for most green pool recoveries because it dissolves cleanly, adds calcium hardness as a side benefit, and has minimal stabilizer. Dichlor is fine for normal weekly shocking. Liquid chlorine is fine for budget-conscious recovery. Avoid trichlor tablets for shocking.
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