Comments for I Can't Get All The Algae Out!

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Aug 11, 2011
by: Robert

Thanks for the reply David

It's really up to you if you want to close the pool a little early. It sounds like that's what you're considering. I've closed a few pools here in Oregon. None in Arizona which is where my pool route was. Lows are in the mid 30's in Winter and it rarely freezes enough to ice over a pool.

But there's a rule for closing and opening pools: Close late and open early. Some people close their pools too early, maybe mid September. You might still have some warm days, into the 70's or 80's. A covered pool can have an increase of 20 - 30 degrees or more when it's that warm. Perfect situation for algae.

If you're going to do a 2/3 drain and refill to get the TDS down, I'd just go ahead and shock with chlorine, clear it up, and enjoy it one last time for Labor Day. Maintain it for as long as possible, then close it as late as you can. All of the other readings are o.k., it's just the algae that needs work.

For the two readings, it could be the test kit that was used, the the experience of the guy who ran the tests, or a combination of both. If they're professionals, they should be using a Taylor FAS-DPD K-2006 or TF-100 test kit. The K-2006 kit is the one I've used since 1999 and the one the Oregon Dept. of Health uses. I know this from dealing with them with public pools and the YMCA pool. I've found it to be the most accurate. I plan on uploading a segmented video I did with the K-2006 kit. I run through all the tests at a local water park. I did this to teach people exactly how to use the kit.

If the pool guys aren't using these kits, ask them to do it with your sample water. Both readings were a bit off but not by much.

Check your chlorine once per week. If you remove the pump and filter you'll need to mix the chlorine manually. Don't just pour liquid chlorine in the pool, that's a sure way to ruin the liner. Use the 5 gallon bucket with water and chlorine and, the best you can, put it around the perimeter of the pool, and then sweep very well. The chlorine should hold pretty well because the water will be very cold. Not a good environment for algae.

How much chlorine will depend on what the reading is. If you keep the chlorine around 1 - 2ppm the algae shouldn't be bad at Spring opening.

Here are links with charts to my chlorine pages:

Swimming Pool Chlorine

Pool Shock

Pool Chlorine

Don't throw tablets into the pool. They'll sink to the bottom and will stain the liner and there's no way to remove a bleached stain. A dose of chlorine every couple of weeks or so to keep the level around 1 - 2ppm should do it. That should be enough to kill some or most of the algae but not enough to stain the liner.

Hope this helps and have a great rest of the Summer.


Aug 11, 2011
Green Algae Pool
by: David

Thank you for such thorough and easy to understand information. I am out of town right now, so I will follow up later.

However, one question I have right away: is it really worth it to go through all of the fuss right now BEFORE I close the pool, or would it be a better use of time and money to just do all of this when I open next year?

Also, what do you make of the differences between the two readings? How do decide whose to follow? Finally, how much and how often should I add Cl throughout the seasons when my pool cover is on (and is incubating algae?

Again, thanks for all the advice!


Jan 18, 2015
Pool Chemical Readings
by: David

Sorry for the delay, but I have my chemical levels. Over the weekend, I added two packets of powdered Cl. The particles on the bottom of the pool still look green, also when I brush it. I went to two different pool stores, with slightly different results. Both samples were from the same area of the pool (deep end), same time of day, on the same day.

Pool is ~25K gallons, 18'x36', with a vinyl liner. Water tempurature is averaging about 76 degrees Farenheit. One store recommended adding another packet of shock while the other told me that I need to add more stabilizer (CYA).

Tell me what you think.

Pool Store #1:
Free Cl: 5.0 ppm
Total Cl: Not Run
pH: 7.9
Hardness: 210 ppm
Alkalinity (w/stabilizer correction): 85 ppm
Cyanuric Acid: 33 ppm
Copper: 0 ppm
Iron: 0 ppm
Total Dissolved Solids: Not Run

Pool Store #2:
Free Cl: 5.0
Total Cl: Not Run
pH: 7..6
Alkalinity: 100 ppm
Cyanuric Acid: 60 ppm
Hardness: 220 ppm
Total Dissolved Solids: 2450
Copper/Iron: 0 ppm
Phosphates: <100 ppm

The fact is that I will be closing this pool around Labor Day, so all of this might be slightly moot; however, I still value your advice and evaluation which I will utilize next spring when I reopen.



Thanks for the readings David. It makes life so much easier for me. We'll go from the top to the bottom with the readings. Even is your chlorine is at 5ppm, you can still have any algae bloom because it's the consistency of the chlorination that kills the algae.

I would suggest getting the pH down to 7.2ppm. Chlorine works better at a slightly lower pH. For a 25,000 gallon pool, you would use 1 qt. of acid.

Get a 5 gallon bucket filled with pool water and then add the acid. Stir with a PVC pipe or stick and broadcast it around the perimeter of the pool. Sweep the sides and bottom to break up any hot spots. Keep the filter running 24/7.

Hardness is fine. Next year go light on the hardness if you can, maybe 150ppm. It's not that important with vinyl pools. If your fill water is already hard there's really nothing you can do about it, but don't add any calcium to the pool.

Alkalinity is fine, between 80 - 100ppm. No baking soda, alkalinity or pH up. CYA is fine. Normal range is between 30 - 50ppm, but you're fine with 60. The total dissolved solids (TDS) are a bit high. 1500ppm is really the max. you want to go. The only way to reduce them is to do a partial drain and refill. And the phosphates...don't even worry about them. Here's a good post about that. Be sure to read the visitor's comments as well:

High Phosphates Over 1000 & Cloudy Water

Next is to shock the pool with liquid chlorine. Do this about 2 hours after you adjust the pH.

Don't shock with regular chlorine granules. It has a pH of 12. If you shock with granules the pool pH will go through the roof and you'll be adding hardness to the pool. For 25,000 gallons, 4 gallons with bring the chlorine level up to 10ppm. Use 4 1/2. It's better to go a little over than under.

Again, get your 5 gallon bucket filled 1/2 with water and then slowly add the chlorine and stir. Broadcast around the perimeter of the pool. Sweep the sides and bottom to break up any hot spots of chlorine. You'll want to get the chlorine level up to 12 - 15ppm. Shock in the evening, then retest the chlorine and CYA in the morning. You'll see how much chlorine has been used through the night.

During this process you can use a PolyQuat 60 algaecide as an added backup against any algae blooms that might occur. The trick in clearing up your pool is to get the pH in line and keeping the chlorine level above 12ppm for a period of time. That's why you shock in the evening, retest in the morning, then shock again.

Be sure to clean the filters every day. Get new ones and swap them out with the old ones. Clean them, and swap them out. Remember to test morning and evening and keep the chlorine level at 12ppm or above as best you can. You may need to do this for a few days.

When the pool turns a white/gray color and you only lose 1 - 2ppm of chlorine through the night you'll know the algae is dead. If the chlorine loss is more you probably still have some residual algae. Let the filter do its job. And keep the cartridges clean.

If you have a pool store that's close, take a sample of water to be tested after every turnover of the water. This is normally about 8 hours. Morning and night. They should do it for free. If you're going to be closing the pool in a few weeks, don't worry about the TDS, but in the Spring it would be good to do a 2/3 drain and refill.

Do this first before putting any chemicals in the pool. If you balance everything out it will be destroyed when you add the fresh water. More time and money wasted. Remember, after you refill with fresh water in the Spring the CYA will bottom out. This is the way you reduce the CYA. Shock with Dichlor. This is a stabilized chlorine and will get the CYA in the pool quickly.

Be careful when using Dichlor as it can get out of hand quickly. For every 10ppm of chlorine added with Dichlor, you'll raise the CYA by 9ppm. Once you reach the 30 - 50ppm mark, switch to liquid chlorine for weekly maintenance.

Hope this helps and have a great rest of the Summer. Let me know how it turns out for you.


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