High CYA and Algae

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T

ThePhysicsGuy

Member
Aug 6, 2019
8
North Amherst, Massachusetts
Hello Folks,

I'm new to TFP and am hoping someone could offer some insight into my situation.

I'm running with a cartridge filter in a 15,500 gallon above ground pool. A couple of weeks ago I found algae starting to grow in my pool that I, and the pool store, couldn't figure out how to cleanout. I found this forum and ordered the TF-100 test kit to find that the reason for my algae bloom was likely because my CYA was around 80, a bit too high for my FC level.

I calculated that it would take about 2 days to refill the pool half-way given that I was on a 2 hours on, 1 hour off schedule to try and not stress my well pump too much. Over the 2 days I still was scrubbing with the brush consistently thinking that with the new water my PPM CYA would go down and free up some of the bleach to do its work. Around 10:30 PM last night my pool became full.

Right after the pool became full I tested my CYA again and it still tested at 80. Being kind of confused I looked again and saw that I could still kind of see the dot and that perhaps it was only a CYA of 60. The dot is a little difficult to see because of the way my lighting refracts off of the water, but I'm hoping someone could offer some insight into water testing and filling a pool. At this time the pool pump wasn't even running yet so the water hadn't properly cycled, but I was still hoping for some results given the 50% water replacement. Which brings about the question: How long after turning the pump on should I test CYA again to get an accurate result?

Before leaving for work I gave the pool a good scrub down with the algae brush and assumed a CYA of 60, so I added enough bleach per your formulas to bring the FC up to 24.
 
There is no set amount of time, size of pump, number of returns, placement of returns, as well as several other factors will effect how well/fast the water mixes up.

You didn't mention pH, but you should have brought that down to 7.2 before you started.

Assuming 60, 24 is the correct number for FC. When you get home, test and bring it back to 24. Before you go to bed test and bring it back to 24.

Keep repeating this as well as brushing once a day. The pump should run 24/7. These are the basics of the SLAM
 
Thanks Tim. My pH was 7.4 (before the addition this morning). It looks like I missed a step, but in reading it sounds like pH readings ride high when you SLAM. Does this mean you shouldn't lower pH when you SLAM, or is only the test inaccurate? I guess what it really comes down to is can I lower pH now given the results of my previous reading or is it too late?
 
The reason why you lower the PH to 7.2 is that chlorine will raise your PH, and as it burns off, become PH neutral. The SLAM levels, which are higher will keep your PH higher as well. Therefore, lowering your PH will maintain the level accordingly. Please note that with AGP (Above Ground Pools), a SLAM usually takes longer unless you have an oversized system. This is due to the return and skimmer being so close in proximity. Why AGP are built this way is beyond me. There should be at least 2-3 returns scattered all over the pool. Even heaters suffer for this reason.

Follow the instructions of the SLAM and maintain the levels as best as possible (morning and night). Do not shut off the pump and be patient as you will get there. The CYA test is subjective as well. To be on the safer side, always round up to the next level when maintaining chlorine levels or performing a SLAM.

!!! Please add your Signature !!!
 
Thanks for your logic.

About why AGPs are set up as they are, I assume the reasoning is mostly aesthetic. Being that all of the plumbing is above ground you'd see PVC pipe all over the place which wouldn't look as great as the less-efficient way they are typically setup. What do you think about leaving my pool vacuum connected and propping it against the opposite end of the pool while I SLAM? This wouldn't skim the surface, but I could do that manually while it takes in water from the bottom of the opposite side of the pool.

To give an update I went home at lunch and did another CYA test — this time I performed the test outside where I had better lighting. I found CYA just barely above 50. Like if I were to add 1 or 2 more drops it would've been 50. No less, I rounded up to 60 CYA. I found that my FC had dropped down to 20 PPM FC so I added 2 quarts of bleach. When I got back home early this evening (after the sun was over the pool but before sunset) the pool was down to 20.5 PPM FC so I added 7 cups, both of the 12.5%.

Something else interesting of note is that when I put in the bleach around noon time the water looked almost like a lime green color — not a fresh bright algae green, but a little washed out. Earlier this evening when I went to test again it looked like a pale pea soup color. I'm not sure if it's because of the difference in lighting or if something is actually happening in there. I'm keeping my fingers crossed either way.
 
ThePhysicsGuy said:
What do you think about leaving my pool vacuum connected and propping it against the opposite end of the pool while I SLAM? This wouldn't skim the surface, but I could do that manually while it takes in water from the bottom of the opposite side of the pool.

Something else interesting of note is that when I put in the bleach around noon time the water looked almost like a lime green color — not a fresh bright algae green, but a little washed out. Earlier this evening when I went to test again it looked like a pale pea soup color. I'm not sure if it's because of the difference in lighting or if something is actually happening in there. I'm keeping my fingers crossed either way.
Click to expand...
Anything you can do to get "more" circulation in the entire pool will help. Along the lines of what you are saying, I have hooed up my vacuum to one skimmer and left the other open. These along with a main drain in the deep end increased the circulation.

You wan to see a color change. What many people do is stand at teh top of their steps and take a picture looking down each day. It may not seem like much as it is happening, but looking back you can see a remarkable change.
 
As Tim mentioned, please take a picture daily around the same time in the same area. Your eyes can be deceiving and lighting will throw colors off. My white steps sometimes look like something is on there (depending on the sun/overcast), but when I go under water with goggles, nothing. Trust the test results and the daily pictures. Your pool will clear up and yes work off the higher CYA level.

The vacuum idea is a great idea, however do this an hour later after you skimmed the surface. It does not take long to skim the top of the water. Then you can leave the vacuum in the pool, just disconnect the hose and repeat the process. Tip the vacuum sideways and be careful not to tear the liner.

As for why they build AGP like this, I do not know. There have been half a dozen times that I recommended this to people and the answer form PB is "NO", we can do this later. Guess what, it never happens later. Everyone is in such a hurry. If one hard piped and ran up the wall, clearly the aesthetics portion of the pool would not be too bad. Even one more return eye ball would be great, but everything should be spaced out. A total of 3 returns and one skimmer is all a pool really needs.

My pool is over kill. In the spring, upon opening, the pool water takes less than 3 hours to full clear up, front dirty to crystal clear. I would be curious to know how long a SLAM would take, but then again, the probability is SLIM to none unless I leave for 3 weeks during the hot summer months as no one does anything.

Please take some pictures of the progress and eventually upload for our viewing pleasure. Thank you.
 
Ask and you shall receive. I present you 50 Shades of Green:

https://imgur.com/UFWyBKH
https://imgur.com/xuofLre
https://imgur.com/EdzldvQ
https://imgur.com/cbylAIU
https://imgur.com/FuDggZu

This is my progress since Tuesday, oldest to newest, taken a little more than one picture per day. The last picture was from around 6:30 AM this morning. My first OCLT required 8 cups of 12.5% bleach, while this morning only required 3 cups, so the pool is definitely making progress. I removed my stairs prior to SLAM process so I could more easily reach those hard-to-get spots with the algae brush, but I think it's easy to see progress without the stairs in place.
 
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After the results yesterday morning, I came home yesterday afternoon and swapped out the filters. Here is the dirty one:

https://imgur.com/PB23mId

Also, the water this morning:

https://imgur.com/RnCAHzA

The water test this morning showed a FC level of 23.5 PPM, 0 CC and the water is clear. I'm going to do another OCLT tonight given no additional bleach prior to make sure everything is good.

While the water is clear, it does have a greenish tint to it. I suspect this is the result of a chemical reaction between the high level of FC and metals in the well water. I don't have copper in my well, but there is a low amount of iron. I'm going to try and filter this out on my own, and perhaps use a combination of a sequestrant and CuLator prior to opening the pool for next summer.
 
If you fail the overnight test, allow your levels to drop down under 10 ppm before you test again. There is a lot of testing error at higher levels given the amount and frequency of drops from the test kit. I would not put too much emphasis on the greenish tint. Look at the water through a clear glass. A lot of times, the light, tree surroundings, etc. will make the water appear green. If you see the greenish tint under a light in the kitchen with a clear glass, then the water is green.

As an FYI, the water tint (if any) will clear up in a few days. The high chlorine levels sometimes create a change in color and some members have reported this. Luckily, I have never had to SLAM my pool because I found TFP real early on.
 

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