Why does my chlorine keep going away

[Beth0277]

I’m a first time pool owner who is frustrated. We have a saltwater pool and have someone checking it weekly to help balance it until we learn. Everything is balanced except the chlorine keeps going down. I have been following the guidance on the pool math app. I’ve added liquid chlorine as recommended and it will look great for a day but then the chlorine goes down again.

I think we have algae. Every morning there is a black line on the shelf that I brush off but it keeps coming back. There is no cover on it but I think it’s algae and is causing the decline of chlorine. I feel like I should treat for algae. Does this picture look like algae? Would you treat for it? If it’s not algae, what is using up the chlorine? The pool is two years old. Everything is working as it should be, I believe. Salt level is good. Help!

 

[PoolStored]

Dunno yet.
Post a full set of results. FC, CC, pH, TA, CH and CYA.
If you are using Pool Math, and you use the same login/pw as TFP, you can share your logs and we can see them (gear upper right, enable sharing with TFP).
I you don't have pool math, get it. Link-->PoolMath
Do this test tonight. Link-->Overnight Chlorine Loss Test
If you Fail, you SLAM to clear the pool. Link-->SLAM Process

 

[Beth0277]

Dunno yet.
Post a full set of results. FC, CC, pH, TA, CH and CYA.
Do this test tonight. Link-->Overnight Chlorine Loss Test
If you Fail, you SLAM to clear the pool. Link-->SLAM Process

I’ll work on getting the full results posted. In the meantime, I have a question.

This morning, my free chlorine was around 1.6 and this even it is pretty much zero. I see the test says to test overnight but what do I do if I have no chlorine now? It was overcast today and no one swam so I wouldn’t think the sun used up too much?

 

[PoolStored]

Sun can consume up to 3-5 FC per day.
Your FC is very low. What is your CYA?

 

[Jimrahbe]

Beth,

Pools use about 2 to 4 ppm of FC (Chlorine) each day when things are 'perfect.'

Just for fun, let's assume your pool does not have algae... How is the 2 to 4 ppm of FC being replaced each day?? This is what your Saltwater Chlorine Generator (SWCG) does..

But, SWCG's have no brain, they have no clue how much FC is in your pool water. It is up to you to test, and then decide if you need to increase your SWCG's output or reduce the SWCG's output..

So, please tell me the following..

What brand and model SWCG do you have, and what is it's rated output???

How long do you run the pump each day?

What is the Stabilizer (CYA) level in your pool??

Do you see a trend here??? You need the ability to test your own pool water so that you can take care of your own pool.. No pool guy will take care of your pool like you can.

Thanks,

Jim R.

 

[Beth0277]

Sun can consume up to 3-5 FC per day.
Your FC is very low. What is your CYA?

CYA is around 70
PH 7.6
Alkalinity 80

 

[Beth0277]

Beth,

Pools use about 2 to 4 ppm of FC (Chlorine) each day when things are 'perfect.'

Just for fun, let's assume your pool does not have algae... How is the 2 to 4 ppm of FC being replaced each day?? This is what your Saltwater Chlorine Generator (SWCG) does..

But, SWCG's have no brain, they have no clue how much FC is in your pool water. It is up to you to test, and then decide if you need to increase your SWCG's output or reduce the SWCG's output..

So, please tell me the following..

What brand and model SWCG do you have, and what is it's rated output???

How long do you run the pump each day?

What is the Stabilizer (CYA) level in your pool??

Do you see a trend here??? You need the ability to test your own pool water so that you can take care of your own pool.. No pool guy will take care of your pool like you can.

Thanks,

Jim R.

I believe it’s a Pentaire Intellichor. I have it set to 40 but my pool tech has done a few boosts to 100 for 24 hours (last one was last week).

Pump runs 24/7

CYA is around 70

 

[Jimrahbe]

Beth,

Please make sure the cell is an IC40 and NOT an IC20.. An IC40 would be perfect for your pool. An IC20 is not...

A CYA of 70 is also perfect and an output of 40% this time a year should be giving you plenty of chlorine...

Running 24/7 is a great way to run a saltwater pool...

Please tell me if you have an automation system, like an EasyTouch or the new IntelliCenter.. I ask because it is possible to run the pump and not the cell 24/7.. I want to make sure that is not happening.

I never recommend using the boost mode.. If the FC is low (which it should not be in a saltwater pool) you need to add Liquid Chlorine, so you can get the FC up quickly..

Unless your cell is not running 24/7, I'd guess that you have algae.. The only way to know for sure to to run an Overnight Chlorine Loss Test (OCLT)

Overnight Chlorine Loss Test

You really can't run any of our tests unless you have the ability to accurately test your own pool water.

The basic idea behind the test is to add enough Liquid Chlorine to get your FC up to about 5 or 6 ppm.. You do this at sun set.. then the next day just before sunrise, you test the FC again and compare that with the first reading.. If you have no algae, the FC numbers should be about the same.. When you have algae, it will consume your FC and the numbers will no longer agree..

Thanks,

Jim R.

 

[Beth0277]

Beth,

Please make sure the cell is an IC40 and NOT an IC20.. An IC40 would be perfect for your pool. An IC20 is not...

A CYA of 70 is also perfect and an output of 40% this time a year should be giving you plenty of chlorine...

Running 24/7 is a great way to run a saltwater pool...

Please tell me if you have an automation system, like an EasyTouch or the new IntelliCenter.. I ask because it is possible to run the pump and not the cell 24/7.. I want to make sure that is not happening.

I never recommend using the boost mode.. If the FC is low (which it should not be in a saltwater pool) you need to add Liquid Chlorine, so you can get the FC up quickly..

Unless your cell is not running 24/7, I'd guess that you have algae.. The only way to know for sure to to run an Overnight Chlorine Loss Test (OCLT)

Overnight Chlorine Loss Test

You really can't run any of our tests unless you have the ability to accurately test your own pool water.

The basic idea behind the test is to add enough Liquid Chlorine to get your FC up to about 5 or 6 ppm.. You do this at sun set.. then the next day just before sunrise, you test the FC again and compare that with the first reading.. If you have no algae, the FC numbers should be about the same.. When you have algae, it will consume your FC and the numbers will no longer agree..

Thanks,

Jim R.

How do I know if I have an automation system? I believe the cell runs 24/7 but guess I don’t know that for sure. I will check if it’s a 40 or 20. Assuming it says that on there.

Also - I am testing using a Taylor kit. Still learning but feel good about it so far.

 

[PoolStored]

CYA is around 70
PH 7.6
Alkalinity 80

Add 10ppm of liquid chlorine, pump running, turn off SWG. Test 30 minutes later, use that as your evening OCLT test. Post result.
Test FC in the morning BEFORE SUNRISE at 6:00am. Before 6. Post result.

 

[Beth0277]

Beth,

Please make sure the cell is an IC40 and NOT an IC20.. An IC40 would be perfect for your pool. An IC20 is not...

A CYA of 70 is also perfect and an output of 40% this time a year should be giving you plenty of chlorine...

Running 24/7 is a great way to run a saltwater pool...

Please tell me if you have an automation system, like an EasyTouch or the new IntelliCenter.. I ask because it is possible to run the pump and not the cell 24/7.. I want to make sure that is not happening.

I never recommend using the boost mode.. If the FC is low (which it should not be in a saltwater pool) you need to add Liquid Chlorine, so you can get the FC up quickly..

Unless your cell is not running 24/7, I'd guess that you have algae.. The only way to know for sure to to run an Overnight Chlorine Loss Test (OCLT)

Overnight Chlorine Loss Test

You really can't run any of our tests unless you have the ability to accurately test your own pool water.

The basic idea behind the test is to add enough Liquid Chlorine to get your FC up to about 5 or 6 ppm.. You do this at sun set.. then the next day just before sunrise, you test the FC again and compare that with the first reading.. If you have no algae, the FC numbers should be about the same.. When you have algae, it will consume your FC and the numbers will no longer agree..

Thanks,

Jim R.

How do I know if I have an automation system? I believe the cell runs 24/7 but guess I don’t know that for sure. I will check if it’s a 40 or 20. Assuming it says that on there

Add 10ppm of liquid chlorine, pump running, turn off SWG. Test 30 minutes later, use that as your evening OCLT test. Post result.
Test FC in the morning BEFORE SUNRISE at 6:00am. Before 6. Post result.

Can you help me know how much liquid chlorine that is equal to? I have one of these bottles attached. 19,700 gallon pool.

 

[PoolStored]

Two gallons. Add the one, that should get you to 5, which is plenty for the test.

 

[Beth0277]

Two gallons. Add the one, that should get you to 5, which is plenty for the test.

Done! I’ll test it in 30 minutes. Is it a huge deal if I don’t turn the swg off? I know how to turn everything off (one button for pump and all) but not just the swg. My husband knows but is already asleep for the night - lol. If it’s a huge deal, I can try to figure it out.

 

[PoolStored]

Is it a huge deal if I don’t turn the swg off?

Yes. Big deal. We are testing your FC loss without UV. If > 1, you have algae. SWG will add FC overnight.
No big deal if you need a day to figure out how to turn off SWG tomorrow and do OCLT tomorrow night.

 

[mknauss]

How do I know if I have an automation system?

Post pictures of your equipment pad. Include any boxes attached to a wall.

 

[Beth0277]

Yes. Big deal. We are testing your FC loss without UV. If > 1, you have algae. SWG will add FC overnight.
No big deal if you need a day to figure out how to turn off SWG tomorrow and do OCLT tomorrow night.

I figured out how to turn the cell off. I just tested and I’m at 8.4 30 minutes after adding. I’ll test again at 6:00 am.

 

[Beth0277]

Post pictures of your equipment pad. Include any boxes attached to a wall.

Will do tomorrow when it’s light outside. I did see that it’s an IC20 when I was just out turning it off. Is it really bad that it’s not an IC40?

I will say, it was running just now at 10:00 pm so I am going to assume it runs 24/7.

 

[mknauss]

The IC20 would need to run 24 hours per day at a high % output during swim season to meet your FC needs.

 

[Beth0277]

The IC20 would need to run 24 hours per day at a high % output during swim season to meet your FC needs.

Is 60 high enough? The only real downside there is the cell will get used up more quickly than if we ran it lower, right? Not sure why previous owners did the 20 but we’ll do more when we eventually have to replace it, I ‘spose.

I’m learning so much!

 

[mknauss]

That adds 2.6 ppm FC IF the cell is on 24 hours per day. In your climate that should be enough right now IF your CYA is at or above 60 ppm and your pool is completely free of organics. I would move it to 80% in the next week or so then monitor FC every day or two.