Cannot maintain FC levels w/ BBB

[Slachey]

All,

I have officially switched to the BBB method and turned off my auto-chlorinator! Due to my use of Chlorine Tabs my CYA reading is ~ 90. My other numbers are as follows; PH 7.6, TA 80. My pool is ~ 17,500 gallons and is an above ground vinyl liner using a sand filter. The water temp has been around 76 over the last couple of weeks.

Based on the high CYA I understand that I must keep my FC high (7 to 12 ppm range), but I am having difficulty maintaining this level w/o adding what equates to a gallon of bleach (6.0% or 8.25%) per day. As an example, at 6pm the other day my FC was at 4.6 so I added (2) 121oz jugs of 6% bleach. By 6:40 am the next morning my FC was 10.6 (expected), and by the next morning it was at 6.6 (not expected). So it lost 4ppm of FC in 24 hours. Is this typical? I like the thought of using the bleach, but this could get expensive if I am adding a 121oz bottle of 8.25% bleach (~ 4.5ppm raise in FC of my size pool) everyday.

At the end if the season (3 more months in the NE) I was going to wither drain / refill to lower the CYA or let it sit over the winter to see if the CYA reduces on its own. Is it easier to "maintain" FC with a lower CYA?

Please let me know if I am doing something wrong here. Thanks!

[BigDave]

Usually chlorine consumption goes down with high CYA. I wonder if you don't have an algae bloom trying to start. Do you have the K-2006? Do you have a CC level?

The overnight test is definitive for chlorine demand. Measure FC and CC in the evening close to sunset. Repeat the FC and CC tests the next morning close to sunrise. If you have CC or you lose more than 1 ppm FC overnight, there's something in the pool being oxidised.

[Watermom]

You may be fighting something in the water which is consuming your chlorine.

In your pool, each of those 121-oz jugs will add about 4.5ppm of chlorine. So, if you had 4.6 in there and added 9ppm more, that would put you at 13.6. But, then you report that by 6:40 a.m. the next morning, you were down to 10.6. That is a loss of 3ppm overnight. When you lose more than 1ppm of chlorine overnight, it is a sign that you are fighting something.

What I am going to suggest is that you go ahead and shock the pool up to 20ppm this evening. Then, a couple of hours after you add the bleach, test the FC and the CC (I assume you have a Taylor K2006 kit?) again and make note of the readings. Tomorrow morning, within one hour of sunrise, test FC and CC again and see how much chlorine you lost overnight.

You need to continue to keep your chlorine at shock level until you can go from sundown to sunup without losing more than 1ppm of chlorine AND you have no greater than 0.5ppm of CC.

Let us know in the morning the results of your overnight test.

[Slachey]

Thanks Big Dave.

There is a bit of green spotting on the liner so that could be it.

Yes we have the K-2006 kit and I will have my wife check for CC tonight. I know that it should be at 0, but what should I do if it is higher? Shock the pool?

Thanks again!

[Watermom]

Dave and I were apparently posting at the same time, but you see that the advice is the same.

[Watermom]

Also, brush the pool while the chlorine is high and run the pump 24/7 while you are working on this.

[Slachey]

Thank you Watermom.

We are going to a baseball game tonight, but I will have my wife shock the pool and we will test late tonight.

Thank you all!

[Slachey]

BTW, can my daughter swim if the pool is at 20 FC?

[BigDave]

With a CYA of 90, sure. Wear an old suit.

[Watermom]

Yes, but she will probably want to wear on old swimsuit that she won't care if it fades some.

[Slachey]

Great. Thanks again. I love this site!

[Slachey]

Good morning.

My wife checked the FC level at 6pm last night and it was 7.8. She said the tested water only turned a very light shade of pink when adding the 5 drops of R-0003. That indicated to her that the CC level was near 0. She added (3) 121 oz jugs of 8.25% bleach. When I got home at 11pm I tested and the FC was 20, and similar to my wifes testing of the CC, the water only turned the absolute slightest shade of pink, so I added 1 drop of the R-0871 and it became colorless. This indicates to me that the CC is near 0. This morning at 7:30 I tested again. The FC was at 18 and the CC was similar to the night before.

So it looks like I lost ~ 2 ppm of FC (assuming a slightly incorrect reading as I tested a couple hours after sunrise).

I did not have a chance to scrub the floor and walls as Watermom suggested and there are small areas of brownish, greenish, yellowish patches sporadically on the pool floor.

What do you guys think?

[Watermom]

Keep the chlorine high again today and brush. I would go ahead and repeat the test tonight.

[Slachey]

Thanks for the quick reply Watermom.

Since the FC is currently at 18, do you recommend that I immediately bring it back up to 20, and ensure it is at 20 pretty much throughout the day and when I test tonight? Or am I ok keeping it in the 18 to 20 "range" throughout the day?

Note that on the pool math calculator, it states with a CYA of 100 that my normal FC range should be 8 to 13 and 39 for shock. With this said, should I go with a higher FC level to ensure I eliminate anything that the FC could be fighting?

[Watermom]

Is the CYA reading 100? Your previous post said 90. 18-25 would be ok but I wouldn't go to 39 especially since you have a vinyl pool. (Not sure where you got the 39 from?)

[Slachey]

Thanks Watermom.

My wife tested the CYA at 90, but I tested at 100. This is a tough test for me, as the disappearance of the black dot is a bit subjective. Must any resemblance of the dot be completely gone including any shadowing?

The FC of 39 came from a Pool Math Chart on Trouble Free Pools. It stated that with a CYA of 100 that my "normal" FC should be in the 8 to 13 range, "shock" is at 39, and "mustard algae shock" is at 54. Sorry if I am mixing apples and oranges and you guys do not follow this.

[Watermom]

The black dot should totally disappear. It is definitely the hardest test to read.

I'm not sure if you are also posting over on TFP, too, or not. TFP was created long after Pool Forum and was basically a spin-off of PF built on the ideas they learned here. (In fact, many of there original members are former members of PF.) However, if you are posting for help on both forums, it is best to choose one or the other. Though mostly similar, we don't totally give the same advice and it makes it hard for everybody if you are trying to use bits of both. Plus it makes it hard for us (and them) to help since we have no idea what advice is being given on the other forum.

Personally, I would not take my vinyl pool up to 39 or 54 unless lower shock levels wouldn't kill whatever type of algae I might have in my pool. Really high levels can bleach out liners. So, I would go with 18-25 and brush and see if that will take care of your issue.

[Slachey]

Watermom.

I am not posting on both forums, I simply did a search for calculating bleach quantities, and that came up. I will use your methods in the Best Guess Chlorine Chart. As there are "ranges" of FC on the chart for "ranges" of CYA, what normal FC range should I be in for a CYA of 90-100?

Thanks again for all of your assistance. Yours and others experience on this forum are invaluable!

[PoolDoc]

There are no absolute ranges, and the data and analysis has continued to develop since I first published the 'Best Guess" chart nearly 14 years ago. Currently, we're not completely sure what happens at very high levels of chlorine, even when the CYA is also very high. It doesn't seem to be a problem for people -- over the past week a local 200,000 country club pool I service has been at CYA=~100 ppm and FC=~25 ppm, with no complaints or problems.

But we're still not sure that a level like CYA=100 and FC=40 won't bleach suits or liners, though we're pretty sure it won't be a problem for 90+% of swimmers. We do KNOW that it's not dangerous, because bleach baths (CYA=0, FC=50 - 100 ppm) have been used by dermatologists for years to treat both adult and pediatric patients.

[Slachey]

Thanks PoolDoc. So would I be safe in a FC range of 8 - 12 for normal everyday use or would you go lower?

[PoolDoc]

With CYA=100, FC = 8 - 12 ppm would be fine.

If you were in an arid region, and using a DE filter, you could probably go lower. But in Pennsylvania, you'd be risking algae if you did so.

[Watermom]

Please don't think I was 'fussing' at you ------ I wasn't. It's just hard to mix and match advice from multiple forums. I hope that we have been able to answer your questions.

Let us know how your overnight test goes tonight.

[Slachey]

Thanks PoolDoc.

Watermom,

No offense taken at all. As mentioned, this site and the replies to my issue have been a great experience so far. I am leaving again for the evening so I added 2 gallons of 8.25% bleach. My FC was down to 13.8 this evening (No CC) from the 18 I measured this morning.

I'll test when I get home tonight and again in the AM.

I hope this stabilizes soon!

Thanks again.

[Slachey]

So I added (2) gallons of 8.25% bleach at 6pm on 6/28 when the FC was at 13.8. I got home at 10pm and the FC was 18. I checked at 6am the next morning and it was at 17. I did not add anything all day yesterday and checked the FC at sundown last night (~ 8:15pm) and the FC was at 12. It lost 5 ppm of FC all day. I checked again this morning at 6am and it was at 10, so it lost 2 ppm overnight. I added (2) gallons this morning hoping to get it up to close to 20 again for the day.

The CC is reading 0, so I am a bit confused as to what I am to do next. The pool is taking at least (1) gallon per day to "maintain" FC level.

Any additional help would be appreciated.

[Watermom]

I don't think you are in 'maintenance' mode yet. I still think you are fighting something in the water.

At 6pm Saturday night you had 13.8. Adding 2 jugs (I assume they are the 121-oz. and not gallons) would have added 9ppm which would put you at 22.8. Four hours later at 10pm, you had already lost 4.8. Then, you lost another 1ppm overnight. So, you actually lost 5.8 from sundown to sunup which is the time period we look at. (When you lose chlorine in the evening when there is no sun on the pool, it is lost due to oxidizing something in the water. When you lose it during the day, part of the loss is to the sun.)

It appears that your chlorine loss is lessening so hopefully you are getting close. I know you are getting frustrated but hang in there. I have a feeling that you are nearing the end. Report back in the morning.

[Slachey]

Thanks Watermom.

I will keep plugging along. Unfortunately we are leaving town tomorrow night and not returning until Saturday morning. That will be 3 full days of sunlight without me monitoring. How high would you recommend that I take the FC into shock level to hopefully keep us out of trouble while we are gone?

[PoolDoc]

Typical usage would be 2 - 3 ppm per day. But it can be much higher with incipient (barely visible) algal growth.


There is a bit of green spotting on the liner so that could be it.

You have NOT reached chlorine levels that would reliably exterminate mustard algae. Typically, that requires levels equal to 30% of the CYA level, or more -- 30+ ppm in your cause -- PLUS brushing.

Chlorine consumption also goes up, somewhat, as the water temp rises.

And, there are any number of pool additives which will create a long term increase in chlorine consumption: any product from United Chemicals, most products specifically for mustard algae, most stain removers, and plus other products we haven't specifically identified yet. Have you used any of those?

Anyhow, if you would, fill out these two forms, so we can be more confident we're not overlooking something:
http://pool9.net/pf-equip-form/
http://pool9.net/pf-hist-form/

[PoolDoc]

How high would you recommend that I take the FC into shock level to hopefully keep us out of trouble while we are gone?

30 ppm or higher.

[Slachey]

Thanks PoolDoc.

Are you saying that I should maintain 30+ ppm instead of 20 ppm that I have been using as shock level for the foreseeable future (i.e. until the overnight loss is 1ppm)?

I don't have the pump / filter info with me, so I will fill out the forms tomorrow.

[PoolDoc]

30 ppm prior to vacation, ESPECIALLY with possible hidden mustard algae.

Then, look at things when you get back. If there is hidden mustard algae, you'll probably have patches of it when you return.

[Slachey]

Thanks PoolDoc.

Last night I took the FC level to 34 at 8:30pm (sunset). At 6am (sunrise) the FC was at 29 (loss of 5 ppm overnight). And at 1pm the FC was 21. I am leaving for 3 days and am very concerned about not having enough chlorine in the pool to last even if I take it to ~ 30.

Watermom said that she would never take a vinyl pool to 39, so I would like to know what is the level I should take it to before I leave, knowing the losses I have been experiencing?

As an FYI, over the last 3 days the pool has been clear and there has been no greenish spots, and the CC is close to 0.

This is getting very frustrating, as I really want this to work, but I cannot see myself continuing to dump gallon after gallon of bleach in this pool everyday. Any further assistance would be appreciated.

Thanks!

[PoolDoc]

Cleaning up is much harder than running a cleaned up pool.

A *SINGLE* episode of algae will often consume more than a month's worth of chlorine! And, mustard algae is the worst. Plus, for unknown reasons, some pools tend to have recurrent episodes of mustard algae.

The fact that you lost 5 ppm overnight strongly suggests that something is still going wrong in your pool. You need to continue raising the chlorine overnight, till the overnight loss is closer to 1 ppm.

Regarding liners, there's no particular answer. Liners vary greatly in susceptibility to bleaching, even within a single manufacturer's product line, and the details that would allow you to predict which is which are generally known only to the companies printing the vinyl sheet stock -- which are NOT the same as the companies making the liner.

The mustard algae guide is here: http://pool9.net/mustard .

And . . .

Anyhow, if you would, fill out these two forms, so we can be more confident we're not overlooking something:
http://pool9.net/pf-equip-form/
http://pool9.net/pf-hist-form/

[Slachey]

Thanks Ben.

I will stick with this method and will fill out the chart when I can. I have had a crazy couple of weeks.

Back to my current situation. How high do you think I should take my FC today, knowing that I will be gone for 3 days?

[PoolDoc]

That's why I was asking for the that info -- so I could advise you better.

Probably your best bet is to keep boosting to near 30 ppm, and hope it's under control when you leave. If you want to take an additional step, borates over 60 ppm permanently inhibit algae, although it's not as effective against mustard algae.

You don't really have time to lower phosphates, if you are leaving this week. That requires that you have sufficient phosphate remover AND can test accurately. It's useless to lower PO4 levels from 2 ppm to 0.5 ppm (500 ppb): it only begins to be effective as you go below 0.2 ppm. The target is 0.1 ppm or less.

But you can raise borates quickly with boric acid: just dump the correct amount (or more) in. Some small pH adjustments may be needed after.

I just finished a dosing guide: http://pool9.net/chart/vacation-dose/ ; there are links to the products in the chart.

[Slachey]

PoolDoc,

So I took your advice and increased my FC to ~ 34 ppm before I left on a short vacation on 7/2. During my vacation I had someone come over on 7/3 and add 3 jugs of bleach to keep the FC high while I was gone. I was not sure what the FC was during this time, but on 7/4 when I came home the FC was 22. Fast-forward to last night at 8:40 pm (a little past sunset) my FC was at 11.2. When I awoke and tested at 5:30am the FC tested at 12??? This was a bit odd, but after I returned at 11am and tested again the FC was at 11.0. I added a 121oz jug of 8.25% bleach at this time as I was not sure if things were completely cleared. I just tested at 8pm (a little prior to sunset) and the FC was 12.4.
.
I don't want to get excited just yet, but I think that I may be on the right track here as the bleach consumption has gone down dramatically.

I'll keep you informed as to my progress.

Thanks again for all your patience!

Slachey

[PoolDoc]

Unfortunately, mustard algae tends to be persistent. Brush the pool as thoroughly and carefully as you can. The goal is to scratch off the slime that protects tiny algae pockets and expose them to chlorine.