Low Free Chlorine (again)

Lawtyger

Well-known member
Mar 11, 2016
94
Tampa, Florida
After getting my FC up to 4 and CYA at 50 I have watched the FC level drop over the last 7 days as follow:

3.5 on 7/13,
2.5 on 7/15, and
1.2 on 7/17.

Chlorinator had been running at 65%. When I saw the 1.2 FC number last night I turned super chlorinate on and ran the pump all night.

Today I am reading 0 to .2 FC.
Salt level is 3300,
PH is 7.5 and
ALK is 60

I thought getting the stabilizer back in there (after getting a bad reading from a pool store previously) and doing my own testing from now on I'd be set. But, losing FC obviously.

Any suggestions on what to check next?

And, I guess I should get some liquid chlorine in the pool to catch things early?
 

cj3737

Well-known member
Jun 14, 2016
629
North Ogden, UT
Sounds like something is eating chlorine or your SWG isn't working properly.. Id add enuf bleach to get you back up to normal operating levels and do an OCLT to see if the culprit is algae

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What is your CC level?
 

Lawtyger

Well-known member
Mar 11, 2016
94
Tampa, Florida
Retested chlorine:

FC = .6
CC = .2

Starting to think, despite enjoying the challenge of maintains my first pool, paying someone may be less time consuming and less prone to whatever I am doing wrong while still learning.

Since it looks like I may be performing my first official SLAM, just to make sure I understand - the shock FC is the number I want to get the chlorine up (probably a duh question but want to make sure.

And, since my CYA is at 50 based on my reading of my test, does the * not recommended mean it is not recommended to keep the CYA at 60 or does it mean I should not shock the pool until I get the CYA up to 70 to 80. I am thinking the latter because waiting for the CYA to go up before SLAM just means I will go without chlorine even longer).

 

cj3737

Well-known member
Jun 14, 2016
629
North Ogden, UT
Paying someone else to do it may screw up your water unless they are TFP method... you could prolly count on your levels being way out of whack and your pool may go green causing more expense.

The shock level is your target level during the slam. The target is your target for normal operations...

Since you have an SWG, your cya levels will be higher than a normal pool. 60 CYA is the low end and not recommended for SWG. If you are going to target 70, I would add a bit of chlorine to get your pool "working" then add a bit of cya to raise to 70 (anywhere between 60-70 will be a 70 target), then you can slam away. Just add enuf CYA to get to 70, then after its all dissolved, you can jump into your slam. 36 oz of stabilizer will bring you up to about 70 CYA. about 1.5 gal of 8.25% bleach will get you up to about 9 FC which will set you up fo ryour slam. Just remember to shut off your SWG during the actual slam process
 

txnole

LifeTime Supporter
Aug 18, 2014
544
Amelia Island, FL
Raise CYA to 70-80 first. The Clorox branded CYA is just fine and easy to use at your pool size, then raise FC using bleach. See Pool Math for exact amount of liquid bleach to add. Once you have your CYA level set, adjust SWG run time accordingly to maintain FC levels at target.

These are not hard changes to implement. You'll be set to jet in just a few hours.
 

nlindelldc

LifeTime Supporter
Mar 21, 2015
429
South Texas
I'm not sure why you would want to raise your CYA before SLAMMING. You will just use more chlorine that way. I would leave it at 50 for you SLAM and then when you are done, THEN raise it up to 80.
 

Lawtyger

Well-known member
Mar 11, 2016
94
Tampa, Florida
Raised CYA to 70. FC is at 13. To get FC back to a 4-6 range, would I just turn the chlorinator off tomorrow while the pool pump runs.

I guess I am curious how much FC would burn off in a day when the chlorinator is off in 90 heat and full sun during the day. In other words, I would go from 13 currently to 4 in a day would I?
 

txnole

LifeTime Supporter
Aug 18, 2014
544
Amelia Island, FL
I'm not sure why you would want to raise your CYA before SLAMMING. You will just use more chlorine that way. I would leave it at 50 for you SLAM and then when you are done, THEN raise it up to 80.
Because it's not at all clear that he needs to SLAM. His pool had low CYA for plaster SWG and was losing FC. Several of us suggested that the root cause may be low CYA, hence... Raise the CYA and then solve the problem.

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Raised CYA to 70. FC is at 13. To get FC back to a 4-6 range, would I just turn the chlorinator off tomorrow while the pool pump runs.

I guess I am curious how much FC would burn off in a day when the chlorinator is off in 90 heat and full sun during the day. In other words, I would go from 13 currently to 4 in a day would I?
I don't think you should expect 9ppm loss in a day. 3ppm may be more realistic.
 

AimeeH

LifeTime Supporter
TFP Guide
Apr 2, 2012
2,028
Columbia SC
Lawtyger

It does appear that your chlorine was either being consumed by something in your water like algae waiting to show itself or your SWG might not be producing enough.

Can you tell us how your water looks?

In answer to your question about letting FC drop, since you already raised your CYA, I'd keep the SWG on for now maybe on a lower percentage and let FC drop slowly. Since you raised your CYA, 13FC is not too high to swim in at 70 CYA.

Have you confirmed that it is indeed 70?

I didn't see what test kit you are using. Can you tell us that?.....or better yet add it to your signature? We'll help you troubleshoot so you shouldn't need a "professional" service as indeed that might cause you further headaches down the road.
 

Lawtyger

Well-known member
Mar 11, 2016
94
Tampa, Florida
Because it's not at all clear that he needs to SLAM. His pool had low CYA for plaster SWG and was losing FC. Several of us suggested that the root cause may be low CYA, hence... Raise the CYA and then solve the problem.
Pool builder stopped by while in the neighborhood building another pool and felt a SLAM was not necessary which goes to your comment that it wasn't clear if I needed to SLAM.

I think I have been treating my pool like I was when I first took over in April when it was finished. The heat (low to mid 90's) and rain from afternoon thunderstorms these last two weeks are conditions totally different then what was occurring in April and May. Yet, i didn't adjust my chlorinator percentage up and as you mentioned had a super low CYA.

Anyway, just really confirming your thought that a SLAM may not be absolutely necessary. I've got the CYA up, I'm not going jump the chlorinator up during this weather to 80 or 90% or higher if necessarily to keep the FC always above 4 this time.
 

Lawtyger

Well-known member
Mar 11, 2016
94
Tampa, Florida
Lawtyger

Can you tell us how your water looks?

In answer to your question about letting FC drop, since you already raised your CYA, I'd keep the SWG on for now maybe on a lower percentage and let FC drop slowly. Since you raised your CYA, 13FC is not too high to swim in at 70 CYA.

Have you confirmed that it is indeed 70?

I didn't see what test kit you are using. Can you tell us that?.....or better yet add it to your signature? We'll help you troubleshoot so you shouldn't need a "professional" service as indeed that might cause you further headaches down the road.
Water looks crystal clear now - very sharp. I am using the Taylor K2006 and will add that to my signature.

I will check the CYA tomorrow afternoon to absolutely verify I am at 70. My wife asked if she and my daughter could go in the pool tomorrow and knowing the FC was at 13 sounded like a scary high number so I was trying to get an idea how much the FC may lower if I turned the chlorinator off. If they can safely get into the pool later in the afternoon I am not so concerned about turning the chlorinator completely off.
 

AimeeH

LifeTime Supporter
TFP Guide
Apr 2, 2012
2,028
Columbia SC
Water looks crystal clear now - very sharp. I am using the Taylor T2006 and will add that to my signature.

I will check the CYA tomorrow afternoon to absolutely verify I am at 70. My wife asked if she and my daughter could go in the pool tomorrow and knowing the FC was at 13 sounded like a scary high number so I was trying to get an idea how much the FC may lower if I turned the chlorinator off. If they can safely get into the pool later in the afternoon I am not so concerned about turning the chlorinator completely off.
If CYA is that high, swimming in 13 FC is NO PROBLEM. It is safe to swim at shock level for your CYA which is more than double your number of 13. Chlorine numbers are dependent upon your CYA. The higher the CYA, the more chlorine is bound to the CYA in your pool. If you want a very detailed Cya/chlorine chart see this link. Chlorine/CYA Chart

Let the wife know that chlorine doesn't turn hair green, copper does. Copper is in a lot of algaecide so.