*Blasting* through bleach - please help me deconstruct this

[rodrigo]

I'm a follower of "THE METHOD" here, and I love it. But something is going on with my pool which I just can't solve. I apologize for how long this will be. I'm including a lot of gory detail at the outset; I can guess what many of the follow up questions will be.

My setup: 11K gallon fiberglass in-ground; SWG; Sand filter; 1.5HP single speed pump timed to run 14 hours daily. Testing is with a Taylor kit (a K2000 starter to which I added the FAS-DPD and other reagents necessary to test CH and CYA). My pool generally balances comfortably at: pH 7.2 - 7.4; FC 4.0 - 5.0; TA 80 - 90; CYA 60 - 70; CH 200. These are an average of recommendations I find here and those specified in the owners manual of my SWG (AquaRite). I have an automatic cover, but it's almost always open because I like to see the pool and I believe sunlight is good for the water.

-- Note: all chlorine additions below are 12.5% bleach; CYA was 40 ppm four days before this all started. I get 10 - 11 ppm FC increase per added gallon. --

Day 1: Early in the a.m the pool didn't look quite right. Test results: pH 7.2; FC 0.5; CC 0.0; TA 80. Something is wrong. Where is my FC? I put the SWG into 'super chlorinate' mode until I could buy liquid. Midday: FC 1.5; CC 0.0; and the pool was mostly cloudy. By 5:30 pm the pool was 95% cloudy and green with pH 7.2; FC 1.0, CC 0.5; TA 80 and CYA 60. I turned the SWG off and added 2.5 gallons of 12.5% liquid chlorine (targeting 25 ppm) to begin the shock (now it's SLAM?) process. Added another gallon before bed.

Day 2: Morning FC 15.5, CC 1.0 -- Bedtime FC 22.5, CC 1.0. 4 gal bleach added over 4 doses, one dose after the bedtime test. Pool was cloudy, but already significantly improved.

Day 3: Morning FC 27.5, CC 1.0 (approx 5.0 overnight loss) -- Bedtime FC 28.0, CC 0.5; 2 gal bleach added in 3 doses, none after last test. Clarity still improving.

Day 4: Morning FC 26.0, CC 1.0 (2.0 overnight loss) -- bedtime FC 34.0, CC 0.5; 3.5 gal bleach added in 4 doses. Clarity significantly improved - nearly clear.

Day 5: Morning FC 30.5, CC 0.0 (3.5 overnight loss) -- bedtime FC 29.5, CC 0.5; 2.5 gal bleach added in 4 doses. Pool is *almost* back to normal-looking.

Day 6: Morning FC 25.0, CC 0.0 (4.5 overnight loss) -- bedtime FC 28.5, CC 1.0; *5.5* gal bleach added in 5 doses, with 5th dose (1.5 gal) after final FC test. I am getting frustrated. Pool looks almost normal. Where is this chlorine going?

Day 7: Morning FC 35.0, CC 0.5 (9.0 ppm overnight loss???), bedtime FC 31.0, CC 1.0; 3 gal bleach added in 3 doses. Pool looks clear & inviting.

Day 8: Morning FC 25.5, CC 0.5 (5.5 overnight loss), bedtime FC 27.0, CC 0.5; *6* gal bleach added in 4 doses.
** Complete test results in early evening - pH n/a, TA *150* (???), CH 320, CYA 45ish **

Day 9: Morning FC 28.5, CC 1.0 (9.5 overnight loss), bedtime FC 31.5, CC 0.5; *6* gal bleach added in 5 doses, 1 gal of which was added after the bedtime FC test. It looks nearly perfect. I hate this pool. My wife is making noises about taking a sample to the pool store for testing.

Day 10 (today): Morning FC 24.5, cc 0.0 (~ 15.0 ppm overnight loss???). 1 gal bleach added so far, and as expected, FC was 37.0 , CC 0.5 approximately 40 minutes and one thorough brushing later.

Additional notes:
- Monthly CYA test was 40 ppm four days prior to the start of this mess. At that point I added 3 lbs dry CYA via a sock in the skimmer targeting 70 ppm; pH was 7.4 at that point. At no point after that did I see it drop below 7.2.
- Pump has been running 24/7 the entire time
- Pool is completely brushed, bottom included, at least once daily, but usually twice. Until Day 4 or 5 water clarity decreased slightly after brushing. After that, brushing did not noticeably impact clarity.
- Vacuumed by hand on Day 5. There was some tree debris on the bottom, but really nothing much.
- Vacuumed by hand on Day 9. No debris on the bottom to speak of, but I felt like I should go through the exercise.
- Backwashed the filter twice over the above period, though I never hit the 20% pressure increase threshold. Filtration is a 200# sand filter with a bit of DE added.
- FAS-DPD reagent comes from a 16 oz bottle purchased late in the 2011 season, and which is stored in the basement when not constantly refilling the dropper bottle. The DPD powder comes from a 4 oz bottle purchased at the same time, and stored in the same conditions.

My issues:
- As the pool clarity improves my chlorine consumption only appears to increase. I undertand the need for patience but I've averaged a 41 ppm FC consumption *per day* over 9 days, for half of which the pool looked completely clear.

- Did my TA suddenly spike because of all this bleach? I wasn't aware that could have an effect. I don't want to add acid because I really have no idea what my pH is (While at work the afternoon of Day 8 the FC slipped down to 16.5. I measured the pH at 7.5 knowing it would skew high due to the FC level). I should ignore the TA until my chlorine holds and I can accurately measure pH, yes?

- And finally, what happened that triggered this episode? At first I assumed my SWG cell had gone bad (this is its 5th season of service). I'm pretty good about maintaining the cell, with monthly inspections and periodic acid-washes. I've never noted any scale on it. However, the control unit never gave any indication of a misbehaving cell. The voltage and amperage while generating didn't change (that I noticed). So now I'm wondering if something got established in my pool and my SWG suddenly just couldn't keep up?

- I added 3 lbs of dry stabilizer to my skimmer in a sock, which I acknowledge was a lot. It took a couple of days to fully dissolve. Did this alter the pH enough at some point that I screwed up the balance? Even though I never measured a pH below 7.2?

I know what I need to do, and that's keep dumping in the bleach. But I've averaged a 41 ppm daily consumption rate when I'm accustomed to seeing 5. Where is all this *&^%$ bleach going?

Any advice & commentary appreciated.

 

[duraleigh]

Re: *Blasting* through bleach - please help me deconstruct t

CYA was 40 ppm four days before this all started

Then your SLAM value should be around 16 ppm or so. Why are you dosing so high (which partially explains the chlorine loss)?

Have you read the SLAM article in Pool School? You seem to understand the process but are not following the suggested guidelines

 

[Bama Rambler]

Re: *Blasting* through bleach - please help me deconstruct t

One thing I notice in your writeup is that it looks like you're only testing and dosing twice a day. Is this true or am I missing something?

You now have a total of ~80 ppm CYA. You really should have waited until you completed the SLAM process to raise it.

Have you checked behind the light and any other penetrations?

 

[rodrigo]

Re: *Blasting* through bleach - please help me deconstruct t

I'm sorry, in my effort to be both thorough and brief, I was confusing.

The CYA adjustment was made before all this began. I measure CYA roughly every 4 weeks, and my last routine test measured it at 40 ppm. I target 70 ppm due to the SWG (owners manual specifies 60 - 80) so I added 3# dry stabilizer. This was the the last significant adjustment I made before the problems started, and is my reason for shocking at such a high level. So even though the last measurement was 40, I had to assume it was more like 70. I didn't bother testing immediately because I understood it took a week or more for CYA additions to reflect in the test... Is this not the case?

** EDIT -- I take it back. I just looked at my log again and see that I did test CYA on Day one, and it was 60 ppm. I missed it before. I apologize. But this begs the question of how it ended up back down at 40 - 50 8 days later... **

So when I tested all levels on Day 8 (11 days after the additional CYA), my CYA was only at 40 - 50 ppm. Is this a reliable result? I feel, as a rule, I should only try to adjust one factor at a time. So I am ignoring the other parameters until I get the chlorine sorted out... unless advised differently here.

I didn't want to clutter the writeup with all my test results. Most days I tested and dosed six times daily. There was one day I was only able to test three times (Day 7). Twice I tested & dosed 7 times. I can post all the intermediate testing and dosing if it will help? I have tried hard to get home and test it as many times as possible each day.

The pool doesn't have many penetrations to speak of. The skimmer opening gets brushed a little more vigorously than the rest of the wall, as does the fish eye fixture for my light (fiber optic). I'm also very careful to get every surface of the steps and even brush the edge of the concrete deck surrounding the pool. My pool has never been this clean.

 

[Bama Rambler]

Re: *Blasting* through bleach - please help me deconstruct t

Sounds like you're doing everything fairly correctly. They aren't fertilizing near you are they?

 

[rodrigo]

Re: *Blasting* through bleach - please help me deconstruct t

Fertilizing? Hmm... good question.

There is a cornfield almost immediately adjacent to our yard. It's about... oh... 150-200 feet or so from the northern edge of the pool. But it's separated by a lot of trees and a privacy fence. Plus, the corn is beginning to dry out already, so I can't imagine they're fertilizing now.

I had not considered some other chemical influence from elsewhere in the environment...

 

[Bama Rambler]

Re: *Blasting* through bleach - please help me deconstruct t

I know they're starting to crop dust around here and while they're no where close to me, they can wreck havoc on pools near the fields.

 

[y_not]

Re: *Blasting* through bleach - please help me deconstruct t

So what is your actual CYA reading and how old is your reagent?
Do you test outside, in daylight, waist level, back to the Sun?

Whatever your CYA is, that's what you have to match your FC to for SLAMing, using the chart in PS.
CYA can be broken down by a bacteria, but this generally happens over the course of the winter and in a swamp like pool.
Maybe you have some of this in there, or you're backwashing far more water than you realize, thus when you top it off it dilutes it.
Possibly a mysterious leak somewhere? Or massive evaporation, because in actuality you're pool is located in the Mars desert??

You ABSOLUTELY MUST check behind that light, behind the skimmer sealing plate even. I would even check behind the return eye fitting nuts. These latter 2 aren't common, but I have seen it here and there.
See here for evidence.
think-i-may-have-found-my-fc-demand-issue-t65957.html

 

[rodrigo]

Re: *Blasting* through bleach - please help me deconstruct t

thank you for the link to that thread. It was a very interesting read!

CYA reagent was purchased this year... maybe May or June. I don't recall exactly. I do the test according to instructions, outside at waist level. the test I did on day 1 was at 5:30 in the evening, so it wasn't exactly broad, blazing daylight in which I did the test. The test on day 8 was at 4:45 pm, so the sun may have dropped behind the neighbor's trees by that point as well. So it wasn't full daylight in either case... but it wasn't twilight either. The CYA reagent is cheap. I don't mind running that test often. I'll do it again.

My light is a fiber optic setup, so it's configured a bit differently than a normal light. There is a clear fish-eye shaped cover forming a watertight seal over an opening that is about the same size as the returns. The fiber optic cable just gets pushed through a dry conduit and rests behind this lens. There isn't a typical light niche exposed to the water. However, with that said, there are still edges and crannies I guess which could bear some extra-thorough scrubbing. Plus, I will absolutely pull out the return eyes to scrub behind them. I appreciate that tip.

 

[rodrigo]

Re: *Blasting* through bleach - please help me deconstruct t

You ABSOLUTELY MUST check behind that light, behind the skimmer sealing plate even. think-i-may-have-found-my-fc-demand-issue-t65957.html

Props to you, Tony. I took a close look around my skimmer. I ran my fingernail along the back of the face plate inside the skimmer opening and *all kinds* of black stuff started flaking off and getting sucked into the skimmer. I was flabbergasted. I scrubbed thoroughly with a small brush. I ended up breaking some of the exposed sealant loose, so I suspect I'll need to replace that at some point. But the algae (black? ) seemed to take up comfortable residence on the surface of the silicone bead.

I've scrubbed it a number of times between last night and this morning. It will continue to get special attention.

I lost 4.5 ppm FC overnight. I retested CYA and it's now down to 30 (we replaced a lot of water due to the backwashing -- bit that is a much larger decline from I expected ). So the quantity of my chlorine doses can be correspondingly reduced.

 

[y_not]

Re: *Blasting* through bleach - please help me deconstruct t

Ghetto Fabulous!!
Glad you found the culprit, almost no one finds any there, but hey, it was worth checking as it can hide aaaaaannnyyyywhere!
Glad it panned out.

Care to post a pic of where it was?

It sounds like FC consumption is reducing?
BTW, when did you last clean and flush the sand bed of your filter as per my Sig?
I don't mean backwashing.
If not, do it ASAP! It makes a woooorld of difference and should be done yearly.

Hang in there and keep your CL levels elevated to shock level in accordance to your cya, as you continue the SLAM process.