Problem with SLAM

mikefamig

Well-known member
Jul 10, 2017
295
Connecticut
Each year that I open my pool here in New England I have the same problem, it takes until mid June to get the water to clean up to the point that i lose zero chlorine overnight and maintain it.

I perform the SLAM and have twice gotten a good OCLT only to have a setback shortly afterwards. The pool is using 0.5 to 1 gallon of chlorine per day. I did an OCLT last night and used 2.5ppm FC. I have again added 1.5 gallons of chloring to get 19ppm FC with CYA = 40. The water is crystal clear.

This has been going on for about a month now. I SLAM, I maintain and get a good OCLT and still the pool uses a gallon of chlorine per day and slips back to a failed OCLT. The only conclusion I can draw from this is that I'm getting a lot of new contaminants in the water daily. This is the third year using the TFP method and each year I've had the same problem. I'm thinking that it's the pollen and other stuf in the air. The pool is near a dozen white pines and a load of Forsythia.

Does anyone have any thoughts? Any help? Am I doing something wrong?

TiA, Mike.
 

AndyTN

Bronze Supporter
Mar 27, 2019
233
Memphis
The first thing I would change is to open it sooner than mid-May. You can help slow the growth of any organics with the colder water and have plenty of time to be patient before it is warm enough to swim. You can leave the cover on to keep out Crud from the trees during bloom and block the sunlight. I know I am in a much warmer location but I normally open my pool by mid-March to get everything all balanced and I leave my winter tarp on until mid-April since I have a lot of trees. You also only have to run the pump a couple hours per day with the cover still on it. Try opening in mid-April next year.

For SLAM, you need to be testing/dosing a least 2-3 times per day. Losing more than half a gallon of bleach a day is very normal for June anyway even with great numbers. Having this prolong for a month when you know you are getting up to SLAM level makes me believe you are not testing/dosing frequently enough. The stuff from the trees isn't helping but certainly isn't your root cause.

I will also say, I have never actually had to follow the SLAM process myself due to opening when the water is still cool and from following TFP methods all year. I just get tannin and iron stains each year :p
 

mikefamig

Well-known member
Jul 10, 2017
295
Connecticut
The first thing I would change is to open it sooner than mid-May. You can help slow the growth of any organics with the colder water and have plenty of time to be patient before it is warm enough to swim. You can leave the cover on to keep out Crud from the trees during bloom and block the sunlight. I know I am in a much warmer location but I normally open my pool by mid-March to get everything all balanced and I leave my winter tarp on until mid-April since I have a lot of trees. You also only have to run the pump a couple hours per day with the cover still on it. Try opening in mid-April next year.

For SLAM, you need to be testing/dosing a least 2-3 times per day. Losing more than half a gallon of bleach a day is very normal for June anyway even with great numbers. Having this prolong for a month when you know you are getting up to SLAM level makes me believe you are not testing/dosing frequently enough. The stuff from the trees isn't helping but certainly isn't your root cause.

I will also say, I have never actually had to follow the SLAM process myself due to opening when the water is still cool and from following TFP methods all year. I just get tannin and iron stains each year :p
We opened in the first week of May but the water never froze last winter here in southern Connecticut. It was a very warm winter with lots of rain and I think that may be a factor in what's happening now. I just pushed the FC level to 30 with a CYA = 40 and lost 5ppm FC overnight. I'm disgusted.

Mike.
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,622
San Dimas, CA (LA County)



 

mikefamig

Well-known member
Jul 10, 2017
295
Connecticut



Thanks but this pool has no lights and the ladders are removed. It is a simple 16 x 32 inground with no accessories.I have used about 64 gallons of 12.5% chlorine so far and I'm just chasing my tail. I have had two successful overnight tests OCLT only to immediately return to very high chlorine usage. It's as if loads of bad stuff is being added to the pool daily.

Mike.
 

AndyTN

Bronze Supporter
Mar 27, 2019
233
Memphis
Is it OK to do the OCLT at a FC level of 30 or should I do it at a lower level? Does it matter?

Mike.
Unless your CYA has doubled suddenly from 40 to 80, FC level of 30 is way too high for your SLAM and a vinyl liner. 40 CYA is supposed to be 16 FC for SLAM.
 

mikefamig

Well-known member
Jul 10, 2017
295
Connecticut
Unless your CYA has doubled suddenly from 40 to 80, FC level of 30 is way too high for your SLAM and a vinyl liner. 40 CYA is supposed to be 16 FC for SLAM.
I'm aware of this and have been doing the SLAM at 16-20 but raised it to 30 out of frustration to see if it helps.

Mike.
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,622
San Dimas, CA (LA County)
Is it OK to do the OCLT at a FC level of 30 or should I do it at a lower level? Does it matter?

Mike.
Hard to say. The more drops the bigger the margin of error. It's not all that uncommon for people to find their FC level went UP overnight. You could pass but not really or fail but not really based on one drop out of 60.
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
33,835
Sebring, Florida
Always, Always remember that chlorine loss in ANY pool in the US or the world is either from UV (sunlight) or contaminants (probably algae) in your pool water. When you do the OCLT, you eliminate the UV so the inescapable conclusion is that you have contaminants in your water.

How do you get rid of them? Chlorine!

There is no secret thing hiding in your pool.......you have organic material in there and you must kill it with chlorine and filter it out.

That means SLAM the pool. Done precisely as the article tells you, and I want to emphasize precisely, your pool will stay crystal clear and you will begin normal FC consumption of 2-3 ppm daily. If you shortcut the SLAM process in any way, all bets are off and your pool will likely consume excessive chlorine again just like it has been doing all this time.
 
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mikefamig

Well-known member
Jul 10, 2017
295
Connecticut
Hard to say. The more drops the bigger the margin of error. It's not all that uncommon for people to find their FC level went UP overnight. You could pass but not really or fail but not really based on one drop out of 60.
Good thought, I hadn't considered that. I tried blasting it up to 30 overnight and it made no difference, I still dropped 5ppm. I'm letting it drop back to ~20.
 

mikefamig

Well-known member
Jul 10, 2017
295
Connecticut
Always, Always remember that chlorine loss in ANY pool in the US or the world is either from UV (sunlight) or contaminants (probably algae) in your pool water. When you do the OCLT, you eliminate the UV so the inescapable conclusion is that you have contaminants in your water.

How do you get rid of them? Chlorine!

There is no secret thing hiding in your pool.......you have organic material in there and you must kill it with chlorine and filter it out.

That means SLAM the pool. Done precisely as the article tells you, and I want to emphasize precisely, your pool will stay crystal clear and you will begin normal FC consumption of 2-3 ppm daily. If you shortcut the SLAM process in any way, all bets are off and your pool will likely consume excessive chlorine again just like it has been doing all this time.
I have been doing the SLAM precisely for weeks with over 60 gallons of 12.5% liquid chlorine. I have achieved successful zero loss OCLT twice during that period of time only to return to high chlorine usage almost immediately. It's as if there is a lot of new organic matter entering the pool daily. I haven't been taking shortcuts, it just won't clean up. I've done this successfully for a couple of seasons now so I know what is supposed to happen and I know that it is possible to get the water clean but this year it's not happening.

How often should I be back-washing? I only do it once a week or so.
 

duraleigh

Admin
Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
33,835
Sebring, Florida
You should backwash when your psi reaches 25% greater than the clean pressure.

So, if you pass the OCLT and you then experience high chlorine loss (I assume in less than 4-5 days), you are getting NEW organics (after the OCLT) in your pool.

Where do you think they could be coming from? It is certainly not algae as the high chlorine in your pool would kill that, right? So, there is virtually no other explanation that these organics are coming from somewhere outside your pool, right? Any ideas as to the source?
 

Leebo

Admin
TFP Expert
LifeTime Supporter
Jul 21, 2011
9,716
Eastern Ohio
I have been doing the SLAM precisely for weeks with over 60 gallons of 12.5% liquid chlorine. I have achieved successful zero loss OCLT twice during that period of time only to return to high chlorine usage almost immediately. It's as if there is a lot of new organic matter entering the pool daily. I haven't been taking shortcuts, it just won't clean up. I've done this successfully for a couple of seasons now so I know what is supposed to happen and I know that it is possible to get the water clean but this year it's not happening.

How often should I be back-washing? I only do it once a week or so.
Can you please provide us with a current set of test results from your own FAS-DPD kit and a photo of your pool. We’d like to get a good overview of everything.
 

mikefamig

Well-known member
Jul 10, 2017
295
Connecticut
You should backwash when your psi reaches 25% greater than the clean pressure.

So, if you pass the OCLT and you then experience high chlorine loss (I assume in less than 4-5 days), you are getting NEW organics (after the OCLT) in your pool.

Where do you think they could be coming from? It is certainly not algae as the high chlorine in your pool would kill that, right? So, there is virtually no other explanation that these organics are coming from somewhere outside your pool, right? Any ideas as to the source?
The filter pressure has not risen and the filter has been back-washed recently and it was pretty clean when I did it.

I agree, new contaminants getting into the water daily is where my mind is right now. We have a line of tall white pine trees in the adjacent property and a long row of Forsythia alongside the pool in our yard and they both put a lot of visible junk on the surface of the water that we skim constantly with a net because the system does not keep up with it. Other than that I have no idea what is getting in there. I've struggled with this each spring opening since I started using this method of sanitizing the pool. It has eventually cleaned up in the past after a struggle but this year is the worst yet.

Mike.
 

mikefamig

Well-known member
Jul 10, 2017
295
Connecticut
Sometimes I think that a rodent got in the heater but I can't imagine how that would happen. I use rubber compression type test plugs in the ports for winter storage. For a rodent to get in there he would have to sneak into the open port while I was working closing the pool. I have no idea how to test for that without disconnecting the heater by putting a bypass hose in the plumbing and I haven't come to that yet.

Mike.
 

mikefamig

Well-known member
Jul 10, 2017
295
Connecticut
The chlorine dropped to 18 by last evening and I added 0.5 gallon of 12.5% HCL which adds about 3ppm so I estimate that would bring me to 21ppm. I tested again at 8am and the free chlorine was at 19.5ppm. It is a fail but getting close. I'll continue the SLAM today and retest tonight.

Mike.
 
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