Alkalinity Test Turns Pink/Red

I used a test kit to test my water. The sample turned pinkish red with just the alkalinity indicator drops.

Does that mean my alkalinity is 0? I have approx 20,000 gal water and right now algae is growing faster than I can clean it out.

Thanks for the question

What kind of kit are you using, a K-2005, 2006, or a yellow OTO test kit?

For the K-2006 kit be sure you're using the right amount of Reagents and in the right order.

R-0007 is Thiosulfate, then 5 drops of the R-0008 Alkalinity indicator, then count the drops of R-0009 until it turns from green to red.

If you have green, then one drop later it's red, and you know you're doing everything right, chances are the TA is only 10ppm. This is much too low. To confirm that I'd encourage you to take a sample of pool water to your local pool store for analysis.

If you're using the OTO kit the color should go from blue to a yellowish/clear color. There shouldn't be any red in there.

If you are in the early stages of an algae bloom I'd like to have the rest of your chemical readings:

Chlorine, CYA (cyanuric acid/stabilizer), pH, Calcium Hardness, and Metals (iron and copper).
It makes troubleshooting much easier and the process of clearing up your pool will go much faster.

You can get this done at your local pool store. Without these numbers I'm just guessing at what the problem is.

Get back to me with the rest of the chemical numbers and I'm sure I can help.

To post a reply, or if you have a similar question, you can see your post on the Q&A page in the "Alkalinity" category.

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Hope this helps and have a great Summer.


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Jun 15, 2012
Alkalinity Test Turns Redish
by: Anonymous

I am using an HTH 5-way OTO test kit. I redid all my test this morning and also did the same tests on my tap water. Results were:

Pool Alk still turned redish with the indicator drops; tap turned green with the indicator and turned red with 11 drops

Pool Hardness clear with indicator; tap red with indicator and 12 drops to clear

Pool PH - 6.8; Cl 5; Br 10
Tap PH 7.5; Cl 0; Br 0

My pool is a mess! I have shocked it and put super algecide in it again yesterday but it still looks like I've done nothing at all. I knocked the green algae off the walls and vacuumed all I could before treating. I backwashed and rinsed the filter before adding the chems. The algae shows no signs of dying.

Jun 15, 2012
Red Alkalinity (TA)
by: Robert

Thanks for the readings.

First I noticed the pH is just a bit low. You need to get that to 7.2 using baking soda. Broadcast it around the perimeter of the pool with the pump on. Keep filtering for 8 - 10 hours, then retest and make another adjustment if needed. Use 2 1/2lbs. of bicarb per 20,000 gallons to raise the pH 0.1.

Swimming Pool pH Levels

Pool pH

Next, I need your stabilizer level (CYA). If it's too high, above 70ppm, you need to do a partial drain and refill. If it's low, below 20ppm, use Dichlor to shock the pool. This is a stabilized form of chlorine. Once you reach the 30 - 35ppm CYA mark, stop with Dichlor and go back to regular liquid chlorine. Optimal level is 30 - 50ppm. 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.

You need to shock the pool morning and evening. The trick is to get and KEEP the chlorine level up at 12ppm. Shock, allow for 8 - 10 hours filtering, then retest. When the chlorine level starts to hold better, you're winning against the algae. Keep a log of what you do...times, amounts, dates, etc... Brush and backwash daily.

Green Pools

It sounds like the TA is low. To raise the TA it's 1.4lbs. of bicarb to raise the TA 10ppm per 10,000 gallons.

Pool Alkalinity

Total Alkalinity

Next is the algaecide. This is used for preventative maintenance only, not to get rid of already existing algae. You can use it to augment the chlorine shock in case the chlorine drops to zero, but please don't think that by adding an algaecide it helps get rid of the algae. It doesn't, regardless of what anyone says.

Jun 16, 2012
Starting Over the Right Way
by: Anonymous

Thank you for your comments. I took a sample of water to pool company yesterday. Alkalinity was in fact "0" and that is why the water turned red with the indicator drops.

I added 30 lbs of Azure Alkalinity Booster in 10 lb intervals finishing this morning. I kept the filter off for 1 hour, then ran 6 hrs before the next dose. I will retest in approx 5 hrs, add 5 lbs of liquid shock and 9.36 oz of algaecide and should be back to normal.

It already looks better and the test after 20lbs of alk booster was greatly improved. I will keep track of this level and go forward with baking soda for pools (it is cheaper). This will also be my FIRST test in the spring. 0 alkalinity eats chems in a matter of hours and very expensive fighting a losing battle. It did cost
$33 to purchase the amount I needed BUT now my opening chems will actually work.

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