Could Milkweed be eating up my chlorine?

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kennethm

0
Dec 4, 2016
4
Sarasota, Florida
I've enjoyed my pool for about 10 years with not much trouble, weekly pool-service, etc. Installed a new SWG 6 months ago to replace the original one, and it has been working great.
HOWEVER....about 5 days ago, pool service tech told me chlorine was down to 0 and asked if I wanted him to apply liquid chlorine? (Since it had been 3.5 or 4 PPM just a couple days previously (measured by me with the recommended Taylor Test Kit on TFP--as well as similar measurements via pool store), I wondered if the SWG had some kind of hiccup. So I told him not for a couple days.

Instead, last Friday I added about 64 oz of 8% bleach as per pool math....48 hours later I tested again....No chlorine. Doesn't even turn pink after adding 3 or 4 ladles of the Taylor powder to prepare for the chlorine drops test.

So today...I added about 86 more ounces of chlorine....and 4 hours later tried to test for chlorine. Same thing...(after the powder was added and I let the sample sit for 15 minutes, got a little blush of pink color...but color vanished after 1 to 2 drops...so chlorine was either nothing or less than 1 ppm based on this test reading (had filled the tube to the 10 ml line).

SO...CYA is about 90; (has always been kind of high...and all has worked fine for years at that level). TA is generally around 120, ph around 7.7 or so...(our well water supply generally has high TA so muriatic acid is needed wheneever we replenish the pool). (Though these measurements are my average and as of 10 days ago...haven't re-done them all just now)....

The SWG voltage and amps and lights are normal, salt ranges from 3100 to 3000....(rose to around 3200 after all the bleach added today)....

BUT WHERE HAS ALL THE CHLORINE GONE? And why can't I see any measurement of FC after adding all that bleach? This has never happened before.

My only idea: This outdoor pool without screening is in the middle of a milk-weed invasion. Little tendrils of weed puffs floating all over the top of the pool. Has been happening for about a week. \
Could all that milkweed (while almost no users in the pool) be consuming the chlorine somehow, throwing everything out of kilter?

Why else would a SWG that has been working great, is 6 months new and not clogged up, PLUS supplemental bleach (maybe 170 ounces over 2 days) still fail to produce FC on the test either by my service tech or by my own test using the TFP preferred Kit method?
 
Back to basics.......two things consume chlorine. Either organics in your pool or UV from sunlight.

You have reduced sunlight deterioration with a CYA of 90 so organics is about all that's left.

The OCLT should only confirm your rapid chlorine loss so I would go ahead with the SLAM..........there are few options left.

By the way, use one scoop of DPD powder. Adding extra serves no purpose unless your FC is VERY VERY high.
 
kennethm said:
I've enjoyed my pool for about 10 years with not much trouble, weekly pool-service, etc. Installed a new SWG 6 months ago to replace the original one, and it has been working great.
HOWEVER....about 5 days ago, pool service tech told me chlorine was down to 0 and asked if I wanted him to apply liquid chlorine? (Since it had been 3.5 or 4 PPM just a couple days previously (measured by me with the recommended Taylor Test Kit on TFP--as well as similar measurements via pool store), I wondered if the SWG had some kind of hiccup. So I told him not for a couple days.

Instead, last Friday I added about 64 oz of 8% bleach as per pool math....48 hours later I tested again....No chlorine. Doesn't even turn pink after adding 3 or 4 ladles of the Taylor powder to prepare for the chlorine drops test.

So today...I added about 86 more ounces of chlorine....and 4 hours later tried to test for chlorine. Same thing...(after the powder was added and I let the sample sit for 15 minutes, got a little blush of pink color...but color vanished after 1 to 2 drops...so chlorine was either nothing or less than 1 ppm based on this test reading (had filled the tube to the 10 ml line).

SO...CYA is about 90; (has always been kind of high...and all has worked fine for years at that level). TA is generally around 120, ph around 7.7 or so...(our well water supply generally has high TA so muriatic acid is needed wheneever we replenish the pool). (Though these measurements are my average and as of 10 days ago...haven't re-done them all just now)....

The SWG voltage and amps and lights are normal, salt ranges from 3100 to 3000....(rose to around 3200 after all the bleach added today)....

BUT WHERE HAS ALL THE CHLORINE GONE? And why can't I see any measurement of FC after adding all that bleach? This has never happened before.

My only idea: This outdoor pool without screening is in the middle of a milk-weed invasion. Little tendrils of weed puffs floating all over the top of the pool. Has been happening for about a week. \
Could all that milkweed (while almost no users in the pool) be consuming the chlorine somehow, throwing everything out of kilter?

Why else would a SWG that has been working great, is 6 months new and not clogged up, PLUS supplemental bleach (maybe 170 ounces over 2 days) still fail to produce FC on the test either by my service tech or by my own test using the TFP preferred Kit method?
Click to expand...
Welcome to the forum.

You are dealing with the beginnings of an algae bloom, and should perform a SLAM as soon as practical.

How to SLAM

The reason I say this is because you have let your daily FC level dip too low. With a CYA of 90ppm, your absolute minimum FC level is 4.5ppm (5% of CYA), and your daily target should be 7ppm (7.5% of CYA).

Chlorine / CYA Chart

If your FC was 3.5 - 4ppm, then zero two days later, and stayed at nearly zero for a few more days, that is an open invitation to an algae party! SWG are fantastic at maintaining a clean pool. Once algae starts to grow (before you can see it even) it can easily overcome a SWG, especially one that is marginally sized for the pool it services.

What makes matters worse, is that with a CYA of 90ppm, that is about as high as the CYA test will reliably go. Your CYA could actually be a bit higher, and you should perform an extended test to get a better CYA level.

Extended CYA test directions
 
SLAM INTERRUPTED: Am I right to pause and start over because the SLAM seemed to hit a barrier?

After trying to SLAM my pool from Monday thru Wednesday, I decided I had erred in starting the process with CYA too high, so I’m taking a pause before trying again. My question now is...how long should I expect a SLAM to take, am I being too impatient, and does the possibility that CYA was too high seem like a good explanation for a barrier to progress after two days?

Here’s what’s happened over the last 2.5 days and 2 nights.

Even though CYA was in the vicinity of 100 (updated now via Pool store).. for my SWG pool, I decided to jump right in and begin to SLAM because I was worried about the speed of the “green” algae-like color taking over the pool and the 0 level of FC that I had never experienced before despite a presumably working SWG
Here’s what happened. Beginning with FC at 0, it took 8.5 gallons of 7.85% bleach to reach FC of 31 PPM. This was Monday at about 3 pm. Avg increase in PPM per gallon of added bleach: 3.65 ppm

About 5 hours later, this had dropped to about 16 ppm of FC..(water still fairly green and not real clear); added about 3.8 gallons more bleach, achieving about FC 32 ppm. Avg increase in FC PPM per gallon of added bleach this time was a little higher...4.2 ppm increase per gallon of added bleach.

Next morning (Tues AM), FC had dropped overnight to FC 24.5..Loss overnight in FC totalled about 7.5 ppm, or 23%. Adding 1.9 gallons of bleach raised this to FC 36 ppm: avg increase in FC PPM per gallon: about 6 ppm.

Tues nite at 8 pm, FC decline seemed to be slowing...reading now was FC 27 ppm. Water looking better. Oh boy, I figured this is working. But after dark and 2.5 hours later, at 10:35 pm, FC continued dropping—to about 23.5 ppm. Adding 1.4 gallons of bleach raised FC to about 33.5 ppm Tuesday night at 10 pm.

To my surprise, on Wednesday morning, though water looked much clearer, overnight the drop in FC did not slow down –FC early morning was 18 ppm, a loss of about 15 ppm or about 45% loss in FC overnight. THIS SEEMED TO ME TO BE A BIGGER AND FASTER OVERNIGHT LOSS in Free Chlorine then had occurred at the start of the SLAM on Night 1. And now the Combined chlorine was about 2 ppm, whereas the previous night it had been closer to about .5

I took this to mean that this process wasn’t making further progress after the first 30 hours. (Was that conclusion correct? ) I figure this may be because high CYA is preventing the shock from being fully effective in combatting the algae or Unknown organic matter in the water—at least with only 33 ppm of FC as my shock level. SO...I am making plans to replace about 20% of my water, rebalance it, and then start anoth er SLAM once there is a lower level of CYA in the pool . Any advice or reaction to this reasoning or this whole unsettling experience?
Thanks very much. And if I’ve got it all mixed up, I'd be happy to try and do better somehow.
 
I took this to mean that this process wasn’t making further progress after the first 30 hours. (Was that conclusion correct? )
Click to expand...
No, it is the wrong conclusion. Don't try to outthink the chlorine. Dose it correctly (as you have done) and then keep it dosed, brushed, vacuumed until your pool is crystal clear
This may take longer than you expect and certainly don't expect it to change suddenly. This is a deliberate process that involves all of the suggestions in the SLAM article.

Follow that article to a T. Don't second guess it or read something into it that is not there. It works as advertised.

Lowering your CYA will be helpful.
 
Dave is SO right! The chlorine was working. You just could not see it with your eyes. Here is you job:

-lower CYA

-Get more chlorine

-Take a picture of your pool looking down at the steps

-take this same picture each day so you can see the difference in the color of the pool. Some days it will be slight others it will be more.

-Follow the SLAM paying extra attention to the M (maintain the FC at SLAM level)

Kim:kim:
 

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Thank you all for very helpful comments. SLAM continues. CYA is lower (it actually dropped by 25% although I was only able to replace maybe 6% of the water...so I do not know just how that happened...but anyway, CYA is now around 70 ppm.

However, my confusion upon reading the recent advice of Dave S. in his recent post seems to be this: I was assuming (and the SLAM directions seem to suggest that) each day while SLAMMING things ought to be tending towards getting a little better. SO I was puzzled, and troubled, so learn that on night 2 the rate at which I lost FC during the darkness seemed GREATER than it had seemed during the overnight on first day. (Okay, I am not keeping exact time-clock records of the number of interval-hours between measurements overnight, and this is a living process, and there can be sampling and measurement errors....and temperatures vary...and maybe it rains on one night....But still: if this is the right process to fix the problem, shouldn't the rate of loss in FC be diminishing as time passes....rather than staying constant or increasing? How am I going to get to loss of 1 ppm FC overnight if instead the loss in FC overnight seems to be getting BIGGER?
 
Could be any number of things. Brushing uncovered some algae, a bird or a squirrel did a drive by night deposit. It won't keep getting bigger forever, stay with it, it always works. Maybe it isn't always predictable day to day but following the SLAM process always ends with a clear pool.
 
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