Introduction, Specifications and a Question

Hello, Everyone.

I've owned a 24' above ground vinyl pool, 13,500 gallon (15k gallon according to the salesman), going on 5 years now. When it was originally installed, it came with the Nature2 system. During the first year, I thought it was the greatest thing in the world. Each subsequent year, I constantly fought algae problems. This year, I've decided to dump the Nature2 system and go with the BBB method. In order to sever my reliance on the pool store, I purchased a Taylor test kit through Watermom's link. I love this kit. While my numbers continue to stay relatively even, the pool store comes up with different numbers each time. It really proves your test results are only as good as the interpreter.

Using the BBB method, I've had stellar results up until last week. We opened around Memorial day to a green hue in the pool, used the BBB method and got it sparkling clear and balanced within a week. Last week we had a heavy rain and the next day awoke to cloudy water and the start of an algae bloom. I had been keeping my FC level in range, according to the best guess chart, and keeping an eye on my pH levels (which were most likely high before the rain).

My numbers before the rain:

FC - 5
CC - 0
TA - 100
CH - 350
CYA - 30 - 35 (I can never figure out when the black dot is considered "gone". At 35, it's only visible if I hold the comparator to my face and squint - it's completely gone at 30)
pH - 7.8+

Before the rain, my pH testing returned a pink-red color. I was working on bringing it back down with some leftover pH Down chemicals I purchased from the pool store last year. After the rain, the FC, CC, TA, CH and CYA hasn't changed much. I'm assuming that my pH was high to start with and the rain kicked the pH too high which, in turn, kicked the algae into overdrive.

After the rain, the pool numbers were:

FC - 3.5
CC - 0
TA - 100
CH - 330
CYA - 30 - 35
pH - 8.0+ (very pinkish red color)

I was able to get my pH into the 7.5 - 7.6 range, and then started the Bleach treatment for the algae. I'm on day 2 of 15ppm chlorine and the pool is improving, but still cloudy with a blue-grey'ish hue. I haven't been able to have confidence in the pH tests since it's likely reading high due to the high chlorine. I'm hoping it's still in the 7.5 - 7.6 range.

So my question: Assuming my pH was too high to start with, will a heavy rain start an algae bloom overnight?

I would like to thank all the contributors and chemical gurus on the site. Without your help over the past 5 years, I would not have had the confidence to switch over to the BBB method. I'm learning more about the pool chemistry, and will have the pool sparkling again in no time.

Thanks in advance!

Quote:

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Originally Posted by DawizNJ

So my question: Assuming my pH was too high to start with, will a heavy rain start an algae bloom overnight?

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No. Usually the reason pools develop algae after rain is because pool owners don't check the water when the weather is bad and their chlorine levels drop too low.

Are you using cal-hypo to chlorinate with? If not, do the calcium hardness test on your fill water and post that result.

By the way, thank you for your kind words. We are glad to have you with us on the forum!

EDIT to add --- please fill in our pool chart with info about your pool.

Pool Chart Entry Form
Pool Chart Results

I filled out the Pool chart entry form and refreshed the Excel'ish spreadsheet, and it seems to have updated accordingly. Thank you for pointing me to that form.

I've been using 6% unscented Walmart/Target bleach to chlorinate the pool. I also have a floater with a 3 inch Trichloro-s-triazinetrione tablet (Leslies Pool leftover from last year), hoping that will slowly increase my CYA level.

My utility water has a CH of 90.

Thanks!

If your fill water has a CH of 90, how did your pool's CH get so high?

Quote:

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Originally Posted by Watermom

If your fill water has a CH of 90, how did your pool's CH get so high?

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That's a question I have as well. In the past, I've always relied upon the pool store to test our water. It's always been in the middle of the expected range when they tested it. Yesterday we ran a sample over to the store for a comparison, and they returned with 210 as the CH level. For all I know, it's been slowly climbing or high for years.

I re-ran the test this morning, on both the pool water and the water from the hose. My test consisted of applying drops of the reagent, swirling to mix, and looking down the comparator tube to the white (red/pink at this point) dot at the bottom of the tube. I applied drops of reagent until that dot turned blue. Maybe my testing process is flawed? I had been looking at the color through the side of the tube, and ensuring the entire thing was blue...which accounted for the higher reading. Which process is correct?

My results:
Pool water: 300
Hose water: 90

I do not fully understand what raises CH levels. I've read that applying chemicals that contain calcium can do it (makes sense). I've used many of Leslie's products over the past 4 years, for whatever they recommended. While that may not be the cause of the CH level, it may have contributed. Sadly, I don't have the ingredients handy.

Also, every year I have to fill in some water from the hose. Even with the application of an Aqua Door and plugging up the holes in the skimmer and return port I still lose water to below the skimmer. I'm hoping that as long as my CH doesn't rise, I can slowly bring it back down into a more acceptable range with those refills.

Thanks for all your help!

You pobably have just used cal-hypo powder to shock the pool with, if you've been operating based on the pool store's recommendations. Don't use any more cal-hypo, and the levels should drift down as you lose/refill water. 300 is a little on the high side, but as long as you keep your pH and TA fairly low, and don't add any more calcium, it shouldn't create a problem for you.

Quote:

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Originally Posted by aylad

You pobably have just used cal-hypo powder to shock the pool with, if you've been operating based on the pool store's recommendations. Don't use any more cal-hypo, and the levels should drift down as you lose/refill water. 300 is a little on the high side, but as long as you keep your pH and TA fairly low, and don't add any more calcium, it shouldn't create a problem for you.

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Ugh, you're 100% correct. My powder of choice was the Powder Plus. I had a bag left over from last year sitting on my shelf. After reading the ingredients, it's 73% cal-hypo.

I'm using nothing but bleach now. Well, except for the tri-chlor tablet in the floater...which I only plan to use until my CYA reaches 50.

Mystery solved!

Hi Daw;

Two quick notes:

1. Let's be sure we're talking about the correct kit (K2006) and not the K2005. When you test chlorine, do you match colors, or do you add drops till the color disappears.

(Your pH test results sound like a possible high chlorine result -- but that's not consistent with your test results UNLESS you have a K2005! Also, pink isn't really a phenol red color, so if you would, read this post: http://www.poolforum.com/pf2/showthread.php?15322)

2. You have a sand filter. If you have left over cal hypo, there is a way to use it up, chlorinate your pool and NOT raise your calcium level further. But we need to resolve any questions about pH first.

Hi, PoolDoc.

The kit reads K-2006 Complete (FAS-DPD chlorine) on the label. The chlorine tests are done using drops until the color disappears.

I ran through the post you linked and saw all the numbers in the tests. As of this morning, my pH test resulted in a orangish-red color. I just got done with a 15ppm shock (it's at 9.5 FC, 0.5 CC now), so I'm going to retest it this evening. Before the shock I was getting an orange color on the pH test.

What was the pH reading?

My water has gotten cloudy again.

Since the last algae cleanup I got the water sparkling clean and made sure I tested the water every morning and evening, focusing on the chlorine levels (using the K-2006 Taylor test kit). Since July 1st, the lowest reading I've gotten was 6.0 free chlorine. Since my CYA has been 30 up until last week, when I increased it to 50, I figured it should be more than enough chlorine according to the best guess chart.

We've had our trees cut down this past week with the last day of work being on the 18th. Some sawdust settled to the bottom of the pool, probably a six inch circle, which I vacuumed up. On the 18th, we had a heavy bather load followed by some rain on the 19th. After the rain, the water became cloudy...although mildly. On the evening of the 18th, my FC was 8.0. On the morning of the 19th, the FC was 7.5. I dumped a little chlorine in the pool when the rain started, since my last algae outbreak happened during some rain. In the evening of the 19th, the FC read 9.0. I did my best to make sure the FC didn't drop too low.

Today, the water is very cloudy - blue in color, with a hint of green. I'm on day 2 of treating it with bleach, trying to keep it at 20ppm. Brushing, Vacuuming, etc. go along with it.

My numbers, as of this morning:

FC 20.0
CC 0.0
CH 290
TA 100
CYA 50
pH 7.4 (before the chlorine shock)

I'm going to do an OCLT tomorrow morning to see if I'm still losing chlorine overnight. I'm confident I'll get the water clean again, but I'm concerned I'm either doing something wrong or missing some fundamental step or understanding.

I had thought that keeping the chlorine levels at 6.0 or higher would prevent the algae from returning, but that appears to be incorrect. I'm wondering what I'm missing? I'd like to prevent this from happening in the future.

I probably haven't provided enough information to determine the cause, so fire away if I have neglected to include some details.