Can't maintain free chlorine at SLAM levels...what am I doing wrong?

[vikinglll]

Hello,

My pool has a little algae problem (Only a few spots of green algae). I tried to SLAM it, however, during the day FC levels went down dramatically. Its hard to keep pouring liquid chlorine (since its a little hard to find). So instead of wasting, I wanted to check if I am doing the right thing (I have read the TFP SLAM procedure).

My pool: 14500 gallons
CYA level: 50
pH: 7.3
FC, before SLAM: 3 ppm (tested using Taylor FAS PPD kit)
SLAM target: 20 (achieved by pouring about 320 oz of 10% liquid chlorine (Pool essential brand from Home depot).

This morning it was 17 ppm...a few hours later it is 10 ppm?

I just cleaned the filter, and there is not much organic material in the pool. The pool is not overridden by algae either.

So what is going on...any advice. Thanks for your time, I appreciate it.

 

[Newdude]

Hey Viking !!

How many ‘few hours later’ we talkin about ? At the beginning of a SLAM, you really need to test and add every 2 hours. You also need to verify you hit your target each time 20 mins later. It sounds like you are verifying, so good job there.

Anywho, the algae will chew through chlorine at first until you stop the exponential growth. Many folks can only add a couple (3) times a day, and while they still make progress, it just takes a lot longer.

For the average pool owner, it’s easiest to start the SLAM on a weekend. Just plan Saturday for babysitting. The 2 hour tests will kill the most algae possible, allowing the FC to hold for 4-6 hours at a time by Sunday. This will allow you to squeeze in some other activities on Sunday and by Monday it is holding long enough to get back to work all day. Usually from there on out the FC holds really well and it’s simply a filtering issue requiring lots of patience and some filter cleaning when it reaches a 25% increase of PSI.

Another thought is your CYA test. How are you testing ? The pool store or test strips are simply guesses at best and you could have very little CYA and if that’s the case, the sun will in fact burn off most of your FC in a short time.

Take a moment when you have one and update your location and fill out your signature. The location doesn’t have to be exact if you like anonymity, but Southeast Nevada or North Dakota will REALLY change our guidance.

List all your equipment with model #s too so we don’t have to ask 5 questions everytime you ask a question. That part can be super specific and still keep your anonymity.

 

[skimmerswimmer]

If you have visible algae, you should expect the pool go through the chlorine quickly. Keep adding to shock level until all of the algae is dead. Eventually, your FC should start to stay around longer and longer but this can take days depending on how frequently you add and how bad the pool is. Eventually, you will lose nothing overnight and if the pool looks good and there is less than 0.5 CC then you're done. Don't forget to brush and clean out all the hard to reach spots as well.

 

[vikinglll]

Updated signature and location. Thanks for the replies....I think I will have to start all over again.

 

[vikinglll]

How many ‘few hours later’ we talkin about ? At the beginning of a SLAM, you really need to test and add every 2 hours. You also need to verify you hit your target each time 20 mins later. It sounds like you are verifying, so good job there.



Another thought is your CYA test. How are you testing ? The pool store or test strips are simply guesses at best and you could have very little CYA and if that’s the case, the sun will in fact burn off most of your FC in a short time.

Thanks for your reply and time. I did update my signature. Answer to your first question: about 5 hours. I did the CYA test using the taylor kit. Also It was not a sunny day. Lastly, its not like the pool is green full of algae, its only in a few spots

Thanks

 

[Newdude]

I did the CYA test using the taylor kit

Ok GREAT !!! So we can trust that it’s right. In this case then, you are losing a lot of FC to the algae bloom. It can be really bad and still be mostly clear. It grows exponentially and there is a razor thin line between pretty clear and pea soup. People can dance that line for a long time thinking everything is ok or not that bad. Your FC loss will tell you how much organics is being killed, but with longer intervals it gets harder to tell because you could have lost 4 PPM to the sun today also.

I think I will have to start all over again.

Keep the FC up as best you can until you have the time to babysit it. As the FC drops considerably down from target, you’ll waste some chlorine not killing the algae as efficiently, but you do not want to get behind the 8 ball here. It could get way worse between now and then. Any lost chlorine between now and then is collateral damage in your favor.

 

[Major_in_MS]

Just want to add, you did not mention brushing. That is a very important part of a SLAM. You really need to hit every surface with a pool brush to break the biofilm that the algae uses to protect itself from the chlorine. Also, not all algae can be seen, at first it is free floating single celled organisms. By the time you start to see those little green patches in a few places, your pool is full of algae that you can not see yet.