Algae Issue - What am I missing??

[Siris21]

Good morning!

Pool:
13,500 Fiberglass
Chlorine pool with Hayward Chlorine Generator (more on this later)

Specs from pool store test:
FC: 6.5
TC: 6.5
CYA: 84 (more on this later)
PH: 7.7
TA: 106
CH: 193
Phosphate: 0
TDS: 1,000

-We were dealing with what I thought was Mustard Algae early in the season, we tried multiple rounds of super shock and it continued to return.

- We then, before coming here, added Yellow-out, which removed the Algae but flipped the pool to Bromine...so we did a total water swap 2 weeks ago without draining, using the method described here. The water was the best it had ever been.

-We are now seeing a dark green, easy to brush algae build-up on the bottom of the splash pool and the main pool. We have tried multiple rounds of shock, as well as rigorous vacuuming and it doesn't seem to go away. The water is clear. We do run a chlorinator, but with the CYA levels already at 84 after the recent water swap, we are going to begin using the SLAM method with liquid chlorine and only relying on the chlorinator when we travel. We test frequently with FAS-DPD kit.

So here are the a few questions and I'm open to thoughts:

1. Is the algae green or yellow?
2. Is the CYA level preventing proper sanitization?
3. Should I drain some water and refill to get the CYA down before beginning liquid bleach?
4. I am trying to avoid putting anything other than Chlorine/Muriatic Acid/Baking Soda/Water in the pool, but am open to other treatment items if you have a suggestion.

Thank you in advance!

 

[Donldson]

Have you done your own CYA test? Unless you added way too much CYA to the water I don't see how a few tabs could have gotten your CYA level up that high in two weeks.

 

[Siris21]

Have you done your own CYA test? Unless you added way too much CYA to the water I don't see how a few tabs could have gotten your CYA level up that high in two weeks.

I have not, I have test strips for CYA, but not a test...it seemed really high to me too...although we drained from the top and filled at the bottom when we did the water swap so it is possible the CYA sunk to the bottom during that process and we didn't remove it all...but I am skeptical at best!

 

[Donldson]

CYA remains evenly mixed in water. Either the test is wrong (pool store isn't exactly known for accuracy, which is why we never rely on it to diagnose a problem) or the no-drain exchange method didn't work correctly which would also mean the bromine problem wasn't solved either.

We would need good data to nail down the problem though. Test Kits Compared

 

[Siris21]

Here is an additional picture of the bottom.

1. I used a TDS meter to measure the drop in TDS to validate the water exchange...we are around 600 on the tap and we were at 1400 prior to the exchange. We dropped to 700 after the exchange which left me feeling like we got almost all of the water out!

2. I'll look at ordering a better CYA test

3. I'm wondering if this is Mustard Algae, it appears green on the bottom, is easy to brush and turns a burnt orange/yellowish color when it enters the water stream after brushing...if so, we may not have shocked high enough to eradicate it.

 

[RLP]

You need more than a cya test, you need the TFP pro, of the Taylor K2006C

 

[Rancho Cost-a-Lotta]

Might be algae, but you need need a proper test kit to confirm by performing an Overnight Chlorine Loss Test. If you determine you do have algae, you'll need the kit to complete the SLAM Process. There are really no shortcuts to having the right tools.

Best wishes!

 

[Newdude]

@Donldson how much mixture is acceptable when attempting a no drain exchange for Bromine? Even if every precaution was taken, a simple breeze mid exchange could stir the water.

 

[Donldson]

@Donldson how much mixture is acceptable when attempting a no drain exchange for Bromine? Even if every precaution was taken, a simple breeze mid exchange could stir the water.

One would want zero mixing, but of course that is impossible. In practice you'd want to bring the bromide below 1 ppm and as close to zero as possible so removing virtually all the original water is needed. But that CYA number is very confusing and would indicate either something went very wrong with the exchange, something went kind of wrong and the original CYA level was in the several hundreds, or the CYA number is completely wrong.

 

[Siris21]

One would want zero mixing, but of course that is impossible. In practice you'd want to bring the bromide below 1 ppm and as close to zero as possible so removing virtually all the original water is needed. But that CYA number is very confusing and would indicate either something went very wrong with the exchange, something went kind of wrong and the original CYA level was in the several hundreds, or the CYA number is completely wrong.

So, the previous owner of the pool had it for 13 years running tabs the whole time...never drained it...so it is likely the CYA was really high to begin with and we missed some of the water. But we did 15,000 gallons to be on the safe side! I will drain some and refill to bring that figure back down!

 

[Donldson]

I will drain some and refill to bring that figure back down!

I did not suggest that. I suggested properly testing your water so you can make accurate decisions.

 

[Siris21]

I did not suggest that. I suggested properly testing your water so you can make accurate decisions.

Test Kit ordered, will get a better CYA number and go from there.

 

[Rancho Cost-a-Lotta]

Test Kit ordered, will get a better CYA number and go from there.

Great choice...you won't regret it.

 

[Siris21]

Great choice...you won't regret it.

Test kit arrived, CYA is at 80, so the next move is to get it down to "normal" range by doing a water swap...then shut down the chlorinator and start with SLAM and Mustard Algae treatment!

 

[Rancho Cost-a-Lotta]

Let us know if you need some help. Best of luck!

 

[Siris21]

We did a partial drain and refill and now we are back with some updated stats from our new Taylor K-2006:

FC: 6
CYA: 32 (A little lower than anticipated)
PH: 7.2
TA: 210 (this is high, and I'm hoping it will come down a little on its own)
CH: 320

Now that CYA is lower we are going to begin daily dosing 24oz of 12.5% bleach and testing FC daily to see what the "normal" demand is. We did a massive shock prior to the water swap which should have knocked the algae down. I think we were dealing with too high of CYA for the FC to be effective.

Thanks for your help, I will continue to keep you posted!

 

[Rancho Cost-a-Lotta]

I think you should rule out algae. I would do an Overnight Chlorine Loss Test to be sure. Won't cost anything except a bit of sleep.

 

[Newdude]

+1. You need to know the algae is gone. It grows exponentially and the last couple of growth cycles are the difference between clear water algae and a swamp.

 

[Siris21]

Will do! I am planning to do that with a few rounds of Shock if needed till there is no overnight loss...right after my inlaws leave! They want to use the pool!

 

[Rancho Cost-a-Lotta]

Will do! I am planning to do that with a few rounds of Shock if needed till there is no overnight loss...right after my inlaws leave! They want to use the pool!

If you don't pass the OCLT, plan on completing SLAM Process. Don't take shortcuts. You have the tools to eliminate algae and to ensure it stays away.