Learned a Lesson - and a question

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C

Cinic

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Jul 24, 2015
194
Tempe, AZ
It had been a relatively event free first winter managing my first pool here in AZ. Relative to summer, chlorine demand went down to almost nothing with the shorter days, lower temps and no swimmer load. I'd almost say it's been on cruise control.

Then a couple weeks ago we had a big wind storm. And the tree near the pool has been dropping a lot of tiny yellow flowers in and around the pool. And I got complacent and didn't get the organics out ASAP. And my complacency continued with a lack of proper testing. And then it started getting warmer and the days longer. And then I walked out last Wednesday and the pool had an odd green tint that I'd never seen before.

So I grabbed a sample and FC = 0. Uh oh - I've got my first algae bloom. pH was about 7.5. So I added a bit of acid before I started the SLAM. TA = 90 & CYA = 70. (CYA has been drifting down with filter back washes since we got the house back in July) I didn't have supplies on hand that night, but I added the last gallon of 8.25 bleach I had on hand. Within minutes the green had faded to whiter and cloudy. A gallon of bleach is worth about 6 ppm FC in my pool (ignore my volume below - that was a best guess).

With my CYA, the chart calls for FC of 28. So I loaded up on bleach and got to work. I kept the FC over 28 and vacuumed a couple times. Backwashed after vacuuming and kept all the baskets clean. Pool steadily looked clearer and clearer. It looked essentially normal yesterday so I decided to give the OCLT a try.

Last night at 6:40 the FC was 29 and then 28 with the same sample. CC is just barely pink on both - >0.5. This morning at 07:00 the FC was 27.5 & 26.5 again with the same sample. No CC to be seen. The test says I need to have a FC drop of 1.0 or less. And with the variability in my testing and depending on how you read the numbers, you could say I'm good (best case) or I still have a demand of 2.5 (worst case). Average would be an FC loss of 1.5.

Any advice? Again, water looks clear. Call it good? Give it another day and try again?

I guess my problem is the variability in the testing. With a 10 ml sample, it seems like it's difficult to be exactly consistent enough when testing at FC levels this high. A tiny bit of variability on the sample size (or drop size) seems to impact the readings by at least 1.0 ppm. I don't want to go to bigger samples for accuracy because I can't count that high with drops.

Any input would be appreciated.

Oh - and the obvious lesson I learned is that I can't get complacent. I need to stay on top of things and temps move around and days get longer. And do a better job keeping leaves and such from accumulating.
 
I've been in your shoes believe me. Drove me nuts, especially when you have high FC levels and each drop at that high number counts. Best advice - keep it simple. You did the right thing going into SLAM mode right away. But you don't want to rush a SLAM. Even when algae is caught at its earliest, a SLAM can take a few days, and it looks like you're on day 4. I'm sure you know the 3 SLAM criteria, so if you have any doubt whatsoever, keep that FC up and do another OCLT just to be sure. Best to be safe to prevent algae's return.
 
Average would be an FC loss of 1.5.
Click to expand...
Keep SLAMming. you can do better.

All drops based tests reach their endpoint when the LAST drop you add makes no difference whatsoever to the color change. Subtract that last drop from your total and the result is the end of the test.

To end the SLAM, you need...

1. Your pool water is sparkling and there is no visible algae (dead or alive)
2. Your CC's are .5ppm or less
3. You can hold your FC overnight without losing more than 1ppm.

You have 2 out of three. My bet is if you do the OCLT tonight, you will pass and be done......then allowing your FC to slide back down to normal range.
 
MarianParoo said:
If you have enough reagents, you might consider the 25ml sample for the OCLT.
Click to expand...

I thought of that for accuracy - but man that's a lot of reagent. I also thought of trying to dilute it down with tap or distilled water. IE - do a 1:1 or 2:1 ratio between 250 or 500 ml of tap to pool water and then just double or triple the FC results. I'd be more confident with margin of error between larger samples so my ratios would be accurate. Then maybe I'd be tempted to do a 25 ml test for accuracy. Although I have no idea how much FC (if any) tap water holds so I'd have to test for that first.

I'm going to give one or two more nights with the OCLT on my standard measuring & sampling. If I keep getting testing variations like above I'll drill down to a more accurate testing method.

There's not too much expense in the SLAM now that the levels are already up. I'd rather be done (and be sure that I'm done) rather than stupidly fight an ongoing battle over the next few weeks.
 
Here's another question: I also have a water feature. I've been running it for an hour a couple times per day during this slam. It introduces a lot of aeration into the pool, so I'm hesitant to run it 24/7 as I can't test for pH with the high FC and I don't want the TA to dip too low. I fight high TA and pH in the summer, but it has been the opposite over the winter. My pH has been very stable lately. My fill water has a high TA so I assume the acid demand reduction is due to lower evaporation and fill water use. Is 2 hours/day enough? Or could I be harboring algae in there?

The water feature is another subject all together. It's on a manual switch only and does not get the daily run that it needs to keep the pipes clean. I'm 95% sure that a Stenner pump is in the near future. So I'll need new timing for that and I'll get the feature on an automatic timer at that point.
 
You can't dilute a sample to do an OCLT. If you dilute the sample 1:1 then the testing error doubles which effectively makes it impossible to measure a 1ppm loss.

Tap water can have anywhere from 0-2ppm FC and between 0.5-1 ppm CCs (if your water provider uses chloramination instead of chlorination). If you ever do any form of dilution, it is best to go to the supermarket and buy DISTILLED water as that will have a pH of 7, little or no TA and no chlorine or minerals in it.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006
 
Is there a valve to shut off the water feature and send all water to the returns? That would be best. It is important to circulate the water in the pool and brush to expose the algae to the chlorine. If you have a 2 speed pump run it on low.
 

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I did two tests last night that were within 0.5 ppm of each other. 29.5 and 30.0. Took extra time to try and be as accurate as possible with the water level. Pool seemed to need less chlorine yesterday during the day. But it there were some passing clouds.

This morning the FC levels were 25.5 and 26.0 for an average drop of 4.0. Clearly something is still going on. So I'm re-stocking the reagents & bleach and will march on with the SLAM.

And thanks to all of you yesterday who advised me to continue with the SLAM. It's like you've seen this story before. :)

Couple questions:
1. How much FC can a small amount of leaves/flowers in the skimmer use? What I emptied this morning wound't have been a handful so I don't think that's enough to account for the FC use.
2. Does letting the FC drop below 28 (shock level for my CYA of 70) do any 'damage' to the SLAM process? The 25.5 is the lowest it's been since I started the SLAM. Am I still inhibiting new growth at 25.5? Or is this allowing 'things' to multiply?
3. I can't babysit the pool during the week and spend the whole day away. How high can I safely elevate the FC before I need to worry about damaging anything? I raised it up to about 34-35 before leaving for the day today. I know I'll lose relatively more to sunlight but I'm OK with that to keep moving forward with the SLAM. But I don't want to hurt any pool equipment or materials.
Thanks again for all the input.
 
I'll try to answer those for you:
1 - Just leaves from overnight aren't what's stealing your FC. That's active algae/organics somewhere in the pool/water.
2 - When the FC drops below your required shock level, it can slow the process down a bit depending upon how long it was low. But it's not a deal breaker. Just increase and try to stay with it.
3 - Going a little higher is not a big problem. During swimming season the biggest concern is to swimmers and clothing. But going too high also can be a waste as the FC will be lowered by the sun and some may not be as productive to the SLAM (algae) as you would like. But going slightly over to help hold during your absence is fine.

- - - Updated - - -

Not sure what items you may have in your pool, but make sure to check any items that may be harboring algae like pool light (and behind them), ladders, under steps, waterfalls, etc. Sometimes those are a treasure-trove for algae.
 
The only thing like that in the pool is a light. I don't know how I'd get behind the light to scrub right now without hypothermia.

My gut is telling me that the water feature is harboring algae. Like I said before I wasn't really good about running that daily. The water feature is 3 concrete 'pots' that are filled from below and the water spills into the pool. I believe it drains back down to pool water level when it's off, but there's still water that's not circulating. The feature draws water from two 'grates' on the side of the pool. So there could be stuff behind there as well. But again, I don't know how I'd get them off right now to scrub behind.

Should I forget my worry about over aeration and leave the feature on all the time? Or is running it twice/day for 30 to 60 minutes enough? I'd imagine if it's really over-run with algae, the FC in the small volume of water in the pipes could get overwhelmed fairly quickly.

Maybe it's not that cold...man I don't want to do that. Although if I'm going to give it a shot, this is the week. Supposed to be in the 90's on Wednesday.


http://www.troublefreepool.com/thre...irst-Day-Today?p=885282&viewfull=1#post885282

Post above shows the water feature. The intakes for the feature is right along the wall on the left side of the photo. Out of view in this shot.
 
If you decide to do a polar dip, please record that for us. :) Ideally, inspecting/cleaning the water feature items would be best, but in some cases you simply have to rely on the bleach to do its job. Depending upon your type of light, some have a retaining ring with a screw that keeps it in place. Removing that allows the light fixture to be pulled-out so you can look behind. It may not be a plausible thing to do right now based on water temps, but may be something to consider as soon as you are able to take a dip. You can run the water feature a bit more, it won't hurt pH all that bad with a little more activity.

- - - Updated - - -

Oh, now I see the water feature (from the link you gave). Very possible stagnant water created an algae home inside. If you ever find a way to inspect from above by pulling the top part off that would be ideal. For now though ...bleach, bleach, bleach. :)
 
Those pots should be sprayed with a dilute bleach solution and any "significant" amount of "stuff" in it should be wiped out with a rag or suctioned out with a shopvac.

This is why we say during a SLAM you should have ALL PUMPS running. If there is any algae or bacteria in the pipes then you will now reintroduce that into the pool and prolong your SLAM.

Turn on your water features and continue with the SLAM.

As for aeration, stop worrying about that now as it is of only secondary importance. You can figure out its impact on pH later.

Don't worry about the light either for now. Get those pots clean.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006
 
The pots are dry when the pump turns off. I believe it back drains down to water level as even the pump strainer basket is empty when I fire up the pump. There is a layer of decorative rocks inside the pots and I do need to remove the rocks and do a good cleaning in there. But more for dust and leaves that get trapped in the rocks. I'll yank all the rocks out and clean tonight before I fire up the feature.

Any algae would have to be somewhere below the pots and deep inside the pipes.

All that being said, I'll turn the water feature pump on 24/7 too until the slam is done.

I need to fabricate some covers for those pots. I'm sick of them acting like giant leaf and dust collectors that then spill into the pool when the feature is on.
 

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