It's not linear it's logarithmic so we round up to the next 10. 41 to 49 is 50 (etc etc). SLAM target is 20 FC.
Intro/Outside Advice
- Thread starter LiquidFlame
- Start date
Okay so I just did my first test after adding 5 gallons of liquid chlorine 3.5 hours ago. FC showed 0.5ppm and CC showed 0ppm. And I tested twice to make sure I didn't screw it up.
Pump has been at 2800 RPM since adding. Am I missing something? Low FC could maybe be expected, but no CC at all?
Pump has been at 2800 RPM since adding. Am I missing something? Low FC could maybe be expected, but no CC at all?
Well it takes FC to make CC. If the FC got depleted quickly, you wouldn't see any now.
But it seems too quick so I want to rule out ammonia. Add to 10 ppm. Test 30 mins later. If you have most of it left, you're good. If you don't, it's ammonia.
The cure is to test/dose to 10ppm FC, every 30 mins until the FC holds. Then get the CYA up and SLAM away.
- Mar 5, 2020
- 3,221
- Pool Size
- 66000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V35
I'd say unlikely that it's ammonia, in this case CC should show up after adding chlorine.
CCs are created by chlorine oxidising nitrogen based stuff, like ammonia, urea, etc. Big problem in public pools with high bather loads, not such a problem in residential pools. Maybe after a pool party, but with properly maintained FC/CYA levels that is quickly dealt with.
FC killing algae usually doesn't create much CC.
Welcome to TFP!
I assume that with your background, you'll be interested in understanding where our recommendations are coming from. Once you get some time to breathe from dealing with your SLAM, I highly recommend going through the Pool Water Chemistry sticky thread in the Deep End. It's important to go through the whole thing before drawing conclusions, as this was also some work in progress at the time.
There is also some more detailed information and summaries in the Further Reading articles in the TFP Wiki, link at the bottom of the webpage.
CCs are created by chlorine oxidising nitrogen based stuff, like ammonia, urea, etc. Big problem in public pools with high bather loads, not such a problem in residential pools. Maybe after a pool party, but with properly maintained FC/CYA levels that is quickly dealt with.
FC killing algae usually doesn't create much CC.
Welcome to TFP!
I assume that with your background, you'll be interested in understanding where our recommendations are coming from. Once you get some time to breathe from dealing with your SLAM, I highly recommend going through the Pool Water Chemistry sticky thread in the Deep End. It's important to go through the whole thing before drawing conclusions, as this was also some work in progress at the time.
There is also some more detailed information and summaries in the Further Reading articles in the TFP Wiki, link at the bottom of the webpage.
- Mar 5, 2020
- 3,221
- Pool Size
- 66000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V35
... Forgot to add: But still a good idea to follow Newdude's advice to really rule out ammonia.
Better safe than sorry. The test is free and quick so there's no drawbacks.
The CYA appears to have held, but it was unreadable prior so maybe this test is an error.
5 gallons of FC loss in 3.5 hours is a bit much for a pool that's been treated for a while. It's not like this is the first addition to a swamp.
Rule it out, then full SLAM ahead.
- Mar 5, 2020
- 3,221
- Pool Size
- 66000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V35
That's what I'm thinking. The chlorine needs to be added anyway.
FC says 11ppm after 30 minutes. So now I'll bring up to 20ppm and test again in an hour
FC 14ppm, CC 1ppm after an hour and 3 more gallons. It still seems excessive since 3 gallons brought it up to 11ppm originally, now it only brought it up 3ppm.
Am I on the right track?
Am I on the right track?
- Mar 5, 2020
- 3,221
- Pool Size
- 66000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Astral Viron V35
Keep the course.
In the early stages of a SLAM you have to top up FC often. The elevated chlorine level helps to kill algae fast, but that also implies that chlorine is being used up fast in the process. The higher the FC, the faster the algae killing, and the faster the chlorine loss. Plus all the losses to UV at elevated FC levels.
Did you make sure to lower pH to 7.2 (or at least making sure it's below 7.5) before going to SLAM-FC, as described in the SLAM article? One of the benefits is that it reduces FC-loss to UV. pH is not a very significant factor for UV-loss at target FC-levels, but quite noticeable at SLAM-levels.
In the early stages of a SLAM you have to top up FC often. The elevated chlorine level helps to kill algae fast, but that also implies that chlorine is being used up fast in the process. The higher the FC, the faster the algae killing, and the faster the chlorine loss. Plus all the losses to UV at elevated FC levels.
Did you make sure to lower pH to 7.2 (or at least making sure it's below 7.5) before going to SLAM-FC, as described in the SLAM article? One of the benefits is that it reduces FC-loss to UV. pH is not a very significant factor for UV-loss at target FC-levels, but quite noticeable at SLAM-levels.
FC 10.5ppm CC 0.5ppm after another hour and no additional liquid added.
pH was at 7.5 this morning and I added a bit of acid before I added the initial 5 gallons. Sun is off the water now so hopefully it stabilizes. Going to add a few more gallons now.
FC 6.5ppm CC 0.5ppm. But added 3 more gallons after I pulled the water.
Also took the opportunity to double check pH and I'm at 7.2 so I'm right there.
Also took the opportunity to double check pH and I'm at 7.2 so I'm right there.
Last edited:
Oly
Gold Supporter
Night time is the right time, no sun losses to deal with and your full SLAM FC level is working directly on your organic contaminants. Check FC early in the morning to measure your overnight chlorine loss and chart your improvement as the SLAM progresses.
FC 4.5ppm CC 0.5ppm this morning.
Going to have to grab more liquid since I ran out.
Going to have to grab more liquid since I ran out.
Oly
Gold Supporter
30k gallons is a big pool. When a big pool goes green it is a big job requiring high amounts of chlorine to eradicate the massive and well established algae. Stay on it, you will make faster progress in no time, but don't be tempted to stop too soon. Algae never sleeps. Also big blue, clear, clean pools are wonderful and easy to maintain with TFP once you are in control. 
FC 14ppm, CC 0.5ppm. Added 2 more gallons.
Maybe a hair clearer but still very cloudy. Hopefully I can keep some chlorine today
Maybe a hair clearer but still very cloudy. Hopefully I can keep some chlorine today
FC 12ppm, CC 0ppm. Adding 4 more gallons.
It seems I can't even get to SLAM level for more than 30 minutes since its burning off/getting used up so quickly.
It seems I can't even get to SLAM level for more than 30 minutes since its burning off/getting used up so quickly.
Oly
Gold Supporter
Take out your frustrations by using your pool brush on the sides, steps and bottom of your pool now. Fix bayonets.
Have you tested at all to verify you are hitting the target 15 mins after adding ? It could be weak / degraded chlorine making it seem like it fell when it never got there in the first place.