Water is clear, CC is 0, but algae is still present?

[asura1]

Hi all,

New pool owner here, ~12k gallon, SWG, sand filter.

Inherited it in less than perfect shape a few weeks ago, then found out the pump had to be replaced. Only got a new one up and running for about a week.

TF-Pro kit is on the way (if I had done enough research, I would have ordered the test a month ago, oh well); during this past two weeks I have only been getting by with test strips from the previous owner, passively adding chlorine to the pool a couple of times a day (not proper SLAM I know) and brushing and vacuuming daily.

The water finally cleared up yesterday and I had it tested at the local pool store for the first time. The results are

FC: 2 ppm
CC: 0 ppm
pH: 7.7
Hardness: 120 ppm
Alkalinity: 180 ppm
CYA: 7 ppm
Copper: 0.2 ppm
Iron: 0.1 ppm
Phosphate: 40 ppb
Salt: 2700 ppm

Clear water and 0 CC sound encouraging, but it looks like there is still dark greenish/yellowish stuff in the pool, especially at the bottom and on the steps, which reappears hours after I vacuum.

Is it possible that algae is still present?

What are my next steps, assuming the test kit is still several days away?

And the most stupidest question, is it okay to go in for a swim in this condition, if not how long should I expect to wait? I really want to swim

 

[Texas Splash]

Welcome to TFP! Let's not try to rush things until your test kit arrives. Good choice by the way. No guesswork and we'll have very accurate results to reply upon. Until then, continue with what you are doing by adding some chlorine each day and brush it around. Start reviewing the SLAM Process page and we'll watch for your test results. Have a good day.

 

[Bperry]

Clear water and 0 CC sound encouraging, but it looks like there is still dark greenish/yellowish stuff in the pool, especially at the bottom and on the steps, which reappears hours after I vacuum.

Is it possible that algae is still present?

“Greeish/yellowish stuff” means there is algae present.

You can safely toss the test strips in the trash, they are worthless like the pool store test. You can add 5ppm of liquid chlorine until your test kit arrives to keep things from getting worse.

 

[asura1]

Thanks both. How do you accurately measure the pool capacity?

My previous estimate was ~12k gal assuming rectangular shape, but today I came across this calculator

Pool Volume Calculator

Check out Pentair's easy-to-use pool volume calculator to calculate the volume of your swimming pool water by choosing the shape, dimensions and depth.

www.pentair.com

That has the option of specifying an oblong shape, which more closely resembles how my pool looks (33 ft long, large diameter 12ft, small diameter 11ft, shallow end 3ft, deep end 8ft - assuming that's the water level we are measuring, not the distance between bottom and top of pool). Going by this I get an estimate of ~14k gal.

However, I'm still not sure that's most accurate, since the deep end of the pool has a ledge that's approx 3ft and it slopes downwards towards the centre. Based on that I think the actual number may be somewhere between 13.5 and 14k.

How much of a difference does a few thousand gal make? Not quite sure which number I should use.

 

[Texas Splash]

How do you accurately measure the pool capacity?

In an ideal world - when filling the pool and checking the water meter. Ha. Hind-sight is 20/20. But estimate the best you can as a start. From there, the PoolMath APP's "Effects of Adding" may be a good indication to assist. For example, if you believe that adding 1/2 gallon of 10% liquid chlorine should increase your FC by X-amount, but you test and find it went much higher, your pool volume much be smaller. Visa-versa if you never reached your goal, the pool volume must be larger.

 

[asura1]

Just to get an idea of what I'm dealing with here, what kind of algae is this?

Also you can see that there are some yellowish stains that cannot be scrubbed off. Is this due to metal buildup? I'm on a well.

 

[Texas Splash]

stains that cannot be scrubbed off. Is this due to metal buildup? I'm on a well.

Most likely yes. Drop a Vitamin C tablet on the yellow stained area and it should lift the stain where the tablet falls.

As for the stuff, maybe it's just the photo, but it doesn't look like algae to me. Looks more like debris that blew in. Can you grab it between your thumb & index finger? Does that stuff go "poof" into a cloud if you brush it?

You're still waiting on your test kit correct?

 

[JamesW]

The stains are probably iron.

The algae is probably mustard algae.

Algae does not usually cause CCs.

Plants, such as algae, create chemicals like glucose from carbon dioxide and water. Using light, the carbon in carbon dioxide oxidizes the oxide into oxygen.

_____________________________________________________________________________

6CO₂ + 6H₂O --> C₆H₁₂O₆ + 6O₂

Carbon Dioxide + Water--> Glucose + Oxygen.

_____________________________________________________________________________

This is how plants make oxygen and store energy in sugars.

The carbon in carbon dioxide is in the +4 state.

The carbon in glucose is 4 at 0, 1 at -1 and 1 at +1.

The carbon is "reduced", which is the opposite of oxidized.

Reduced just means that the oxidation state is lower or reduced because the atom gained electrons which are negatively charged.

When chlorine oxidizes the carbon in glucose back to a +4 oxidation state, it reverts back to carbon dioxide.

_____________________________________________________________________________

C₆H₁₂O₆ + 6O₂ --> 6CO₂ + 6H₂O.

Glucose + Oxygen --> Carbon Dioxide + Water.

_____________________________________________________________________________

C₆H₁₂O₆ + 6OCl^- + 6HOCl --> 6CO₂ + 6H₂O + 6H⁺ + 12Cl^-

Glucose + Chlorine --> Carbon Dioxide + Water + Hydrogen ions + Chloride ions.

_____________________________________________________________________________

This is a similar process to an animal using oxygen to burn sugars to release energy and exhale carbon dioxide.

So, chlorine reacting with algae is mostly an oxidation reaction and not a combination. Algae is mostly converted back into carbon dioxide and water.

Chlorine can combine with carbon compounds, such as methane (CH4) by replacing the hydrogen ions.

Carbon in methane is in the -4 oxidation state.

Algae mostly does not create CCs.

CCs are mostly created by compounds like ammonia where the nitrogen is in the -3 state.

For ammonia, you get combination and oxidation.

So, the CCs eventually go away, especially in sunlight where UV photons knock loose electrons from the nitrogen and make it easier for the chlorine to take them.

Active chlorine is +1, so it bonds with more negatively charged atoms, like nitrogen in the -3 state or carbon in the -4 state.

The carbon in algae has a zero net charge.

So, the reaction of chlorine with algae is mostly oxidation and not combination.

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[asura1]

Can you grab it between your thumb & index finger?

The larger black stuff I can pick up with my fingers.

Does that stuff go "poof" into a cloud if you brush it?

Here is a video when I brush it,

You're still waiting on your test kit correct?

Yes, takes forever to get it shipped to Canada through a third party service!

 

[asura1]

The algae is probably mustard algae.

Sigh, can't be anything else right, wouldn't want to make it too easy for myself

Plants, such as algae, create chemicals like glucose from carbon dioxide and water. Using light, the carbon in carbon dioxide oxidizes the oxide into oxygen.

Thanks for the detailed explanation, I will have to digest this

 

[Texas Splash]

Once the kit makes it in, we'll walk you through everything. No worries. For now though, get familiar with the SLAM Process and keep in mind that with any iron staining or content in the water, we always have to treat algae first. Once the owner passes all 3 SLAM criteria, then we can look into the best options for metal control and/or stain removal. If this turns out to be Mustard, you still do the regular SLAM first to pass all 3 criteria. The only difference with MA is that you go an additional 24 hrs at a higher (MA) FC level to eradicate the MA spores. But we'll come back to that later.

 

[asura1]

I managed to pull the ladder up to get a good look at the inside of the steps, which I haven't been able to brush.



Well, what's the best way to really clean this out?

 

[JamesW]

Replace the treads.

They are no longer safe to use.

 

[asura1]

Replace the treads.

They are no longer safe to use.

Okay will do.

 

[Texas Splash]

Wow. Those were indeed nasty inside. Good catch.

 

[asura1]

Alright folks I just got the test kit. Here are my results,

FC - 9.5/10.5

My eyes were really struggling to tell when it's still light pink and when it turned completely clear. Maybe it's the lighting where I tested - I did it in the bathroom with a very bright light. 19 drops was my count. Did a second test with my wife by my side looking for the colour change and she counted 21 drops = 10.5 FC.

CC - 1
PH - 8.2
TA - 160
CYA - 20 (corrected by PoolStored below)

black dot only disappeared when the cylinder was filled to the brim, I guess that's closest to 30?

CH - 175
Salt - 2,400

 

[asura1]

One more question - when the instruction says "rinse", should I rinse with tap water or pool water? I took it to mean tap water.

 

[PoolStored]

I did it in the bathroom with a very bright light. 19 drops was my count. Did a second test with my wife by my side looking for the colour change and she counted 21 drops = 10.5 FC.

That is within the margin of error for the test...+/-1 drop in 10.

Good read here...Link-->Water Testing Errors - Further Reading

black dot only disappeared when the cylinder was filled to the brim, I guess that's closest to 30?

CYA <20.

One more question - when the instruction says "rinse", should I rinse with tap water or pool water? I took it to mean tap water.

I rinse with tap water and dry with a coffee filter...doesn't leave "hairs" behind. Every couple days I rinse and clean with Alcohol. If I do the salt test I ALWAYS clean with alcohol (rubbing) after every test.

 

[asura1]

Good read here...Link-->Water Testing Errors - Further Reading

"Are you red-green colorblind? It may make it hard for you to distinguish between shades of pink with a DPD test."

I do have a red-green colour deficiency...that explains the difficulty getting that one right

 

[proavia]

"Are you red-green colorblind? It may make it hard for you to distinguish between shades of pink with a DPD test."

I do have a red-green colour deficiency...that explains the difficulty getting that one right

Many color-blind members do NOT have an issue with the FAS-DPD test as for them it changes from "some" color to clear.