Neighborhood pool has been fine, now algae infestation?

[Ethan]

I am a lifegaurd at a private pool in a neighberhood. My boss recently quit and I took on the job of maintaining the pool chemicals. I have some basic experience, having been a gaurd for six years. In the past I've shocked pools, backwashed, vacuumed, etc. Countless times, and never really had much of a problem before.

The pool in question was built in the early 80's and has had the same two pumps since. The former caretaker of the pool used the test kit which has two tubes which take a pool sample and 5 drops of reactant to test for chlorine and ph. No other levels are possible to test with this kit, but there are some walmart test strips. Only thing is they are a coupla months old and I've heard they're inaccurate. The pool is in an L shape with a 12 foot deep end and 3.5 shallow. The deep end leg of the L is about 20 ft wide and around 50-60 ft long. The shallow end of the L is roughly 60 by 30. The pool has had some green moments on and off this summer, but now it isn't doing so good. The water in the shallow end is realtively blue, but a little cloudy. The deep end is a cloudy, green mess. Three days ago the area recieved a heavy rain, and it got progressively worse since. This morning I added about 2 cups of shock ( I know, not enough), and around 10 tonight I added about 10 cups. Yesterday evening I added a bottle of clarifier via a bucket of diluted pool water and another bottle directly into the pool around 2 today. Over the course of today I also added about half a bottle of algecide. The pumps both have chlorinators that I keep stacked with pucks, the deep end pump havng a much, smaller, seemingly less efficient chlorinator stack (which I think is why the shallow end isn't as green as the deep end.)

I'm supposed to be going out of town for 6 days, starting tomorrow. What should I do to get the pool back into reasonable shape? I know that I have to completely kill the algae before it will start to lose the greenish color. How much shock should I use, and how long will it take? Is it possible to completely kill the algae with a single dosing of shock? I have swimmers come on and off all day, with an average of about 5-10 people in the water at a time. I do spend many hours there by myself though.

Also, a chemical exposion took place about 12 miles north of my pool. 70000 people were told to evacuate the neighboring town which is due north and literally shares a border with the town my pool is located in. Although the pool was south of the evacuated area, could this chemical fire have an effect on my pool? It rained pretty hard the day after, which made me think about it. The chemical fire mainly consisted of ammonium nitrate.

Sorry for the long post, but I wanted to gave as detailed a description of the situation as possible. Any quick advise would be awesome. I've already read quite a bit of info on this site and others, but I feel a response to my specific situation would be more useful than somebody elses scenario.

 

[JohnT]

Welcome to TFP Ethan.

You most likely have a very CYA level, which makes your minimum chlorine level and shock level very high as well. Without the CYA number, it's hard to give any advice. You need to raise your chlorine to at least 15ppm, probably a lot higher, and then stay on top of it by testing every few hours. Being gone for 6 days isn't going to help. I hope you can recruit a helper.

Read this article for more information. http://www.troublefreepool.com/pool-school/defeating_algae

 

[Ethan]

What do I use to lower the cya levels? There are two chlorinators for this pool, is there anyway I can lower the cya enough so that the chlorinators will keep my pool at a decent FC level while I'm gone?

 

[JohnT]

What do I use to lower the cya levels? There are two chlorinators for this pool, is there anyway I can lower the cya enough so that the chlorinators will keep my pool at a decent FC level while I'm gone?

The only reasonable way to lower CYA is to replace the water.

 

[Guest]

What do I use to lower the cya levels? T

Replace water. There is no other way. You need to drain and refill but without good test results you are "******* in the dark".

IF you are going to be caing for this pool you need to get a handle on basic water management. Pool School is a good place to start. You also need a good test kit, preferably with the FAS-DPD chlorine test since it is vastly superior to DPD testing. OTO (the yellow chlorine test in the two way comparator) is NOT permitted for commercial pools in just about every state because it does not test for FC but only TC.

 

[Ethan]

The test kit I have is the Taylor k-2005. And I do have a basic understanding of pool chemistry, seeing as Im very aware how important it is to know my cyanuric acid levels. I understand the relation between FC and CYA. As of today I've pretty much takin care of the algae. It is not visible anywhere in the pool. The water color is still ever so slightly green, but I assume that's because of the dead algae particles floating around. My main issue now is the lack of clarity in the water. I have added 1 bottle of blue clarifier each day the last 3 days in a row. I know this stuff combines smaller particles in the pool, making them easier to filter and sometimes sink to the bottom. Is there such a thing as using to much clarifier? Should I add more, or seek a different alternative?

 

[duraleigh]

Should I add more, or seek a different alternative?

To help us help you, you should post a full set of current test results.

 

[Buggsw]

Besides what everyone else asked or recommended...Are you running the pumps 24/7? What kind of filter are you using? Have you backwashed?

 

[Guest]

As of today I've pretty much takin care of the algae. It is not visible anywhere in the pool. The water color is still ever so slightly green, but I assume that's because of the dead algae particles floating around.
IF there is green you have live algae. Dead algae is white!

My main issue now is the lack of clarity in the water.
The algae is not dead. Your water will not clear until you kill all the algae. Keep shocking!

I have added 1 bottle of blue clarifier each day the last 3 days in a row. I know this stuff combines smaller particles in the pool, making them easier to filter and sometimes sink to the bottom. Is there such a thing as using to much clarifier?
IF you are using a polymeric clarifier then it is very possible to overdose with the result of cauding a cloudy collidial suspension in the water that is impossible to clear or filter out.
IF you are using a chitosan based clarifier then overdosing will gunk up your filter media and might require you cleaning it (breaking down a DE filter and soaking the grids in TSP or automatic dishwahwer detergent, soaking a cart overnight they same way, or using an acidic detergent sand cleaner for a sand filter)

Should I add more, or seek a different alternative?

NEVER overdose clarifier. Sometiems it can take a few days for it to work but if you have live algae it's not going to do a thing. If you can vacuum to waste then floc is often a better choice than clarrifer for a commerical pool that needs to be reopened quickly. However, you still need to kill the algae first!

 

[Casey]

I have swimmers come on and off all day, with an average of about 5-10 people in the water at a time.

I hope you are not letting people swim in that pool! It is a death trap if you cannot see the bottom of the pool, especially the 12 ft deep end! Some may think I'm over reacting and that is fine by me but it is *your* job to keep the public safe and if I were the one in charge, I'd shut it down for maintenance, just as I'd shut my own private pool down if it were cloudy or algae ridden. The risk is just too much in my personal, humbled opinion.

I am going to have to dito duraleigh and ask that you post a full set of numbers, even if you have to run a sample to the pool store and have them check it.