Why is my pool water green?

Here is advice and input:

  • Your pool water turned green most likely because of an algae bloom in your pool water. When you shocked the pool and added the copper algaecide you might have oxidized the copper in the algaecide. What I would do if I were you is take a sample of the water (about 16oz.) to your local pool store and have them test for metals.
  • Another possibility is that there is metal in the water, which will react with chlorine and turn green or brown. Many parts of the country have naturally high levels of metal in their water, so this can be a problem any time replacement water is added to a pool. Use Natural Chemistry’s MetalFree or another chelating agent.
  • Algae is probably at the bottom of your pool. I had the same problem; the bottom of my pool was brown. I went to the pool store and they told me to do the following: raise the ph above 8 test ph. Next, 1 lb of yellow out and 1 lb of shock. Run filter, then brush and vacuum. Next 12 hrs later, 1/2 bag of shock. Next 12 hrs later, 1/2 bag shock. Test your chemicals, run the filter, brush, vacuum and you should be good to go. My pool is above ground; 4,500 gallons, so talk to a pool store.
  • Yellow out is shock. By the way, always read the product labels. Mixing the wrong chemicals together pose health risks. Your pool water is green because your PH is out of balance making your chlorine ineffective; therefore your filtering system is not working correctly.
  • Algae is certainly the cause of the green, but an imbalance of pH and/or alkalinity is why you have algae in the first place (while there is adequate chlorine). Very high or low pH significantly decreases the effectiveness of chlorine. I suggest that you test and adjust your pH and alkalinity first (take a water sample to your local pool store and have them test it if needed). Once those are balanced, shock the water and use an algaecide. Run the filter 24 hrs per day and vacuum the dead algae debris often – you’ll also have to clean the filter almost daily. Once the green starts to disappear, add a blue clarifier to help clear the dead algae from the water and eliminate any cloudiness.

The oxidation rate of your chlorine is affected by the pH level. PPM of your chlorine is just a quantity and the oxidation rate is the quality of the water. To properly control a pool, you should use a pool controller that measures the oxidation rate or ORP.

The absolute fix for algae bloomed pool: DRAIN, ACID WASH and REFILL.

Acid Washing an In Ground Pool: Also called a drain; An acid wash becomes necessary if the pool has turned into the “black lagoon”. This may occur if the winterizing process is not done properly, or if the pool has been stagnant for a period of time so that algae has taken over. If you notice scaly, man-phibian creatures splashing around out back, it’s probably time to drain.

Our general rule of thumb for determining the need for an acid wash is: if you can see the bottom of the pool (the floor) then you can usually bring it back with chemicals, labor and extensive filtering. However, once a pool has turned dark green or even black, algae and mold spores have impregnated themselves into every porous depth of the pool surface and are difficult or impossible to remove by traditional cleaning and chlorinating methods.

As a result the pool will continue to spawn new mold, algae and bacteria at an accelerated rate causing the pool to turn green quickly even though you may be vacuuming and chlorinating more. This will play havoc on your filter media such as sand, cartridges or DE, requiring frequent media changes to remove the contaminants.

If the floor is not visible, the cost of the chemicals and labor will generally be greater than the acid wash charge, and take much, much longer. Also, extensive algae blooms will permanently stain and adhere to plastered, concrete and gunite pools, making an acid wash desirable.

An acid wash is, put simply, purposeful stripping of a tiny layer of plaster or concrete, exposing fresher, undamaged and clean material beneath. Therefore, it is ill-advised to make it an annual custom, which will accelerate the need for replastering. Most plaster coats, (sometimes called whitecoat or marcite), are in excess of 1/2″, so a few careful acid washes should not hurt. Pools can also be commercial strength bleach washed or high pressure washed if the effected area isn’t that bad.

Costs to acid wash and empty a pool range between 900.00 and 1200.00 in Maryland, Virginia and DC. If your pool is filled with contaminated water and debris, the cost to drain and acid wash may range from 1600.00 to 2800.00 depending on the degree of contamination and the amount of non-drainable debris that must be removed and disposed of by manual labor.

You may also decide on an acid wash not because of swamp conditions, mold, algae and bacteria but just to bring out a brighter, whiter finish. For mineral stains and/or deposits, chlorine stains, even dirt stains…an acid wash is always a dramatic aesthetic improvement.

If your pool has had years of algae blooms, and if your pool seems to grow algae overnight or just bloom very easily….changing the water and acid washing the surfaces algae sticks to can give you an algae free summer and save you a bundle in lost pool time, labor, filter media and chemicals.

Acid is a dangerous substance. Pool company personnel are specially trained in its application and wear protective clothing and breathing apparatus during the acid wash. To protect our environment, the acid/water waste should be neutralized with soda ash prior to its being pumped to a safe location. In many states, permits may be required.

If it is a clear green, then it is copper. Cloudy green is algae. The best, safest, and cheapest way to remove the copper is by using Alum. The same Alum is used when making pickles; just look down the spice isle in the short bottles.