Algae with Chlorine Lock

[Pool PhD]

My pool is shaded by trees and has suffered a couple of green algae blooms. I have been able to get the water clear by repeated shocking and cleaning the filter. However, I am unable to get my Free Chlorine level up no matter what I do. CYA levels are fine. I have 7 jumbo tablets in my fully opened feeder. I can't seem to get rid of a cloudy sediment on the floor of the pool and stairs. Could this be mustard algae? I think I need to get the Free Chlorine up but no matter how many times I shock the pool the level stays low. Help me Mr. Wizard!

 

[dfwnoob]

Welcome to TFP, I'm glad you've found us! For what it's worth, I think you're seeing dead algae on the floor of the pool.

Couple of things to get out of the way: "chlorine lock" is a made up pool store term and doesn't really mean anything. You have algae because you do not have a sufficient amount of chlorine for your level of CYA. This will inevitably happen when using chlorine tabs since most are stabilized. The water clears up temporarily when you "shock" because you're bringing your free chlorine level to a point where it can start to destroy a lot of the algae. Of course, as you've been seeing, it drops right back down again once it's depleted since there is still active algae growth, even if you can't see it. The TFP methodology, which you'll find is quite minimalist, only recommends two methods of chlorination: liquid chlorine or a salt water chlorine generator.

How are you currently testing? If you're relying on pool store testing, stop. You will need to make the investment in a quality test kit: Either a Taylor K-2006C or a TFTestKits.net TF-100/TF Pro. Both use the same reagents, but the TFTestKits models are a better deal for what you get. If you do not go with the TF Pro (which includes a magnetic stirring device), it is strongly recommended that you purchase a Taylor SpeedStir to make testing signficantly easier and less error-prone.

To get started, I would read the TFP Pool Care Basics. After that, check out the article on the SLAM Process (Shock Level And Maintain), which you will need to follow once you have a good test kit. You'll need to know your actual CYA number and pick up some liquid chlorine before moving forward with that. SLAMs are considered complete when you can pass an Overnight Chlorine Loss Test.

We'll help you get this cleared up and enjoying your pool again.

 

[Dirk]

What a great post, df! Pool PhD, you gotta get one of those kits. The first step is to get a good CYA test result. Chances are good your CYA is too high, and that will have to be dealt with before you attempt a SLAM. No pool store remedy will help if your CYA is too high. That's job one.

100s of 1000s of people have come here with the exact same story as you. We've helped them all. They've all bought one of those kits. We can help you, too, if you're willing to take a leap of faith. Order the kit, perform a full suite of tests when it arrives, post the results here, and the rest we'll help you with. EZPZ.

 

[Pool PhD]

Here is my water test from Leslie's. Until I get a kit, Leslie's is right down the street. CYA level is good. Going to shock with Liquid Chlorine as soon as I can get my hand on some. Seems to be out of stock at a lot of places here in Austin.

 

[PoolStored]

The only thing you should do until your test kit gets there is to add 5ppm of liquid chlorine per day. Until we get an accurate CYA level from YOUR test kit, don't add more, or any other chemical.

Use Pool Math to figure out how much to add to add 5ppm per DAY. Link-->PoolMath

 

[thetekgeek]

@Pool PhD - I'm glad they printed the test results out for you. Unfortunately, it doesn't look like they were printed on 2-ply paper so it won't be good for what I would use it for. Throw the test away and order a proper test kit. While you're waiting for the kit, ADD NOTHING to your water except 5 PPM worth of liquid chorine every day. Once the kit arrives, run a full set of tests and post them here.

 

[dfwnoob]

Until I get a kit, Leslie's is right down the street. CYA level is good. Going to shock with Liquid Chlorine as soon as I can get my hand on some.

The problem is that you can't bring your pool to shock level because you don't actually have any idea what your CYA level truly is, and a SLAM is not a "one and done" dosing. Shock level is a function of the CYA level, and without a reliable test (Leslie's is not that), you're flying blind. Dose the 5ppm worth of LC every day for now, which for a 25k gal pool would take 1.25gal daily.

 

[JJ_Tex]

I love how their 1st suggestion is to sell you something to get rid of the metal in your pool. Removing metal will have zero impact on your algae issue, and did they happen to tell you how you ended up with metal in your pool? I'll give you a hint, its something they sold you, likely algaecide, tabs with "blue" in the name or some other magic potion like PoolRx.

Next they will get you for $50 of phosphate remover, which again will have zero impact on your actual algae issue.

Then they will get you for a couple hundred more $ on other stuff you don't need before telling you you have chlorine lock or your water is "old" and you need to drain and refill.

The only thing worse than a pool store's testing is their advice.

 

[Dirk]

The problem is that you can't bring your pool to shock level because you don't actually have any idea what your CYA level truly is, and a SLAM is not a "one and done" dosing. Shock level is a function of the CYA level, and without a reliable test (Leslie's is not that), you're flying blind.

This is so important to understand. It is the foundation of what we teach here, and what makes our methods work. This is NOT what Leslie's does. They are using arcane chemical maintenance principles and dubious testing methods. We know both to be a fact, based on 1000s and 1000s of stories from our forum users. We are using science and the best testing method available to the average pool owner at a reasonable cost.

Just using tabs and shocking your pool once a week, with a set amount of shock, will not keep algae at bay indefinitely. Eventually your chemistry will break down and you'll need to reset, by starting over with fresh water. Using tabs is what is driving that endless cycle.

For example, I've been running TFP methods for six years. I've never had algae, and I've never had to shock my pool. Not once. I did have to do a small water exchange this year, to combat the calcium accumulation due to my city's very hard water, but I've never had to do so for excess CYA. And I've never had chlorine-lock.

Contrast that with what my pool was like before, when maintained by a professional company. My chemical and maintenance costs were about 10 times higher than they are now. My pool was blasted with acid and chlorine once a week, which made for a very uncomfortable couple of days. And by the end of the week I usually had some amount of algae growing on the sides of my pool. I had so much CYA in the water the chlorine was virtually ineffective (except at burning my skin). The tabs did not maintain the chlorine at a proper level between pool-guy visits.

I have first hand experience with both methods. They do not compare.