Why Did New Pool Water Turn Yellowish Green?

by Leslie
(Chesterfield, Va)

After filling the pool, my children put chlorine tablets in a floater and tossed it into the pool.

Within 12 hours the fresh water had turned to a yellowish-light green color.

We used water from an artesian well.

How do we fix this as it happened a lot last year also.

Thanks for the question Leslie

And I hope all is well in Chesterfield. I'm a Richmond boy myself. Left in 1999 to help with my uncle's pool business.

Correct me if I'm wrong, but an artesian well is slightly different than a "drilled" well.

The water could be a bit deeper and flows naturally without an aid of a pump. It also is filtered through layers of rock, where a drilled well is mainly surface and/or ground water that has not necessarily been filtered.

Ground/well water is subject to contaminants and high metal content such as copper and iron.

A good page with some information can be found here:


I'm not all too familiar with artesian wells, but these are some of things I know.

Some water in artesian wells do tend to have a light yellow/brown colored water.

Some wells have a kind of "tank/brine tank" setup. One is a softener and the other tank is a media filter of some sort.

If either one sits for a long period of time, it may be a good time to get it serviced and the media replaced.

Don't try to flush out well. You might stir up silt or clay which could get into the water.

I would encourage you to get your well water tested by a local pool store. Have them test for pH level,
alkalinity, hardness, heavy metals, and total dissolved solids (TDS).

The TDS should not be over 1500ppm. If it is you might need to bring in some water from a pool water delivery company. You can't keep adding the same water and get different results.

Pool Water Delivery

If your well water has metals you will need to use a metal sequestrant to prevent your pool from metal stains. Or you can use a water delivery service. Their water should be metal free and ready to go, already balanced out.

Sequestrants bind to the metals and prevent metal staining.

All sequestrants break down so you'll need to regularly dose your pool to maintain the correct level.

ProTeam's Metal Magic

Jack's Magic the Pink Stuff (regular)

Blue Stuff (new plaster)

Purple Stuff (SWG)

These are some good products.

Sequestrants with HEDP, phosphonic acid, or phosphonic acid are the most effective.

If you have an emerald green color, more than likely this is a pH issue that can be resolved easily.

Swimming Pool pH Levels

Swimming Pool Chemistry

Keep your chlorine level between 1.5 - 3.5ppm and cyanuric acid (CYA/stabilizer) between 30 - 50ppm.

Swimming Pool Chlorine

The chlorine tabs are good maintenance but will result in the CYA increasing. The only way to reduce that is to drain 1/3 - 1/2 of the water and refill.

Be sure your using Trichlor tablets.

From what the question says, I don't think you have any kind of algae problem. It could be you have pretty good well water but you're having a chemical reaction when chlorine tablets or other chemicals are put in the pool.

Now it needs to be adjusted for pool water.


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