Will Draining Water Help With Algae?

Jump to latest Follow Reply
Once we understand your CYA level then lower your pH to 7.2
Wait 30 minutes for it to mix then start adding LC to raise the FC to the desired level.
Your TA is fine and we can address CA after but you have a vinyl pool so no big deal.
How does the fill look now? Is there a lot of algae? Can you see the bottom in deep end?
 
HermanTX said:
First I want to ensure we have the right CYA. You mention "just above 30" so we always round up so your CYA was 40. Could you see the dot at 40 and not at 30? If so then it is 40 which implies a FC for SLAM of 16ppm

We all use the
PoolMath app. It helps determine amount of chemical based on pool size. Do you have it?
Click to expand...
Yes, I have the Pool Math app. It's very handy!

For the CYA test, I could easily see the dot at 40. At about halfway between 30 and 40, it started to fade, but it was still visible. It became just invisible with the water level slightly below the 30 mark - maybe less than 0.5mm below that line. In reality, I should probably just consider it 30. Here is a pic:

View recent photos.png
 
HermanTX said:
Once we understand your CYA level then lower your pH to 7.2
Wait 30 minutes for it to mix then start adding LC to raise the FC to the desired level.
Your TA is fine and we can address CA after but you have a vinyl pool so no big deal.
How does the fill look now? Is there a lot of algae? Can you see the bottom in deep end?
Click to expand...
There's definitely some algae in there - some dead stuff I can see sitting on the shallow end floor. I can't really see the 8ft deep end. I put the robot vacuum in and could barely see it down there. Overall, the water is pretty green.
 
ugadawgs311 said:
Yes, I have the Pool Math app. It's very handy!

For the CYA test, I could easily see the dot at 40. At about halfway between 30 and 40, it started to fade, but it was still visible. It became just invisible with the water level slightly below the 30 mark - maybe less than 0.5mm below that line. In reality, I should probably just consider it 30. Here is a pic:

View attachment 487852
Click to expand...
OK - it is important that we target the correct SLAM level as it will frustrate you when it is taking longer than you may have expectation for. The better you maintain your SLAM level the better the process will go.
I would do 1 more CYA test - pour the solution to the 40 mark - can you see it? Then pour the solution to the 30 mark - can you see it? If so use 30, if not use 40 as your CYA. Don't try to measure in between the lines - just go to 40 then to 30 and make your decision on which then set your SLAM level FC to either 12 (for 30 CYA) or 16 (for 40 CYA)
 
HermanTX said:
OK - it is important that we target the correct SLAM level as it will frustrate you when it is taking longer than you may have expectation for. The better you maintain your SLAM level the better the process will go.
I would do 1 more CYA test - pour the solution to the 40 mark - can you see it? Then pour the solution to the 30 mark - can you see it? If so use 30, if not use 40 as your CYA. Don't try to measure in between the lines - just go to 40 then to 30 and make your decision on which then set your SLAM level FC to either 12 (for 30 CYA) or 16 (for 40 CYA)
Click to expand...
Is there any harm in just opting for 16 FC? That will use more chlorine, which will cost me more $$$, but is there any other harm in doing that? If not, that may seem like the safest route to make sure SLAM works and the pool gets clear.

EDIT: based on my first test, yes I could see the dot at 40. I could not see the dot at 30.
 
  • Like
Reactions: HermanTX
ugadawgs311 said:
Can I use it to lower PH safely?
Click to expand...
We at TFPC recommend the use of muriatic acid to lower the pH of pool water.
However, with a vinyl pool, no heater or SWCG, you can use up that product if you wish. It is Sodium BiSulfate. That will leave sulphates in your water. If those build up, they can destroy metal, concrete, etc. So continued use is not recommended.
 
  • Like
Reactions: HermanTX

Enjoying this content?

Support TFP with a donation.

Give Support
mknauss said:
We at TFPC recommend the use of muriatic acid to lower the pH of pool water.
However, with a vinyl pool, no heater or SWCG, you can use up that product if you wish. It is Sodium BiSulfate. That will leave sulphates in your water. If those build up, they can destroy metal, concrete, etc. So continued use is not recommended.
Click to expand...
Thanks for the info. I have an old container (about a quarter gallon full) of MA, but it’s at least 6 years old, if not older.

I’ll try the Clorox first since. Hopefully just one dose of it will do the trick.
 
HermanTX said:
Ok so your SLAM FC target is 16ppm. Maintain that by testing every 3-4 hrs and top up with liquid chlorine to maintain a level of 16ppm.
Click to expand...
I thought the CYA level is when the dot becomes invisible. In my case that was 30.

When adding LC, should I wait until the sun goes down or cloudy days? My pool gets sunlight almost all day long.
 
ugadawgs311 said:
I thought the CYA level is when the dot becomes invisible. In my case that was 30.

When adding LC, should I wait until the sun goes down or cloudy days? My pool gets sunlight almost all day long.
Click to expand...
CYA level is the level at which you last saw the dot. So if you saw it at 40 but not at 30 then your CYA level is 40. Use that for SLAM as well as normal FC levels.

With a CYA of 40, you have sufficient protection from UV so start now with the SLAM, once you have lowered your pH. There is no reason to wait till tonight. It only prolongs the SLAM process. Just remember to test every 3-4 hours during the day and early evening to keep your FC level at 16ppm

Initially you will lose a lot of FC quickly because it is attacking the algae, so stay on top of it. Also, continue to run your main filter pump 24/7.
Continue to brush and if you can vacuum to waste any of that stuff on the bottom then that will help remove it and not clog up your filter.

Report back any issues or questions.
 
  • Like
Reactions: Mdragger88, Newdude and ugadawgs311
HermanTX said:
CYA level is the level at which you last saw the dot. So if you saw it at 40 but not at 30 then your CYA level is 40. Use that for SLAM as well as normal FC levels.

With a CYA of 40, you have sufficient protection from UV so start now with the SLAM, once you have lowered your pH. There is no reason to wait till tonight. It only prolongs the SLAM process. Just remember to test every 3-4 hours during the day and early evening to keep your FC level at 16ppm

Initially you will lose a lot of FC quickly because it is attacking the algae, so stay on top of it. Also, continue to run your main filter pump 24/7.
Continue to brush and if you can vacuum to waste any of that stuff on the bottom then that will help remove it and not clog up your filter.

Report back any issues or questions.
Click to expand...
Thank you! I just added the PH Reducer, so I'll let that circulate for about 2 hours, then test the water. If the PH level is 7.2, I'll begin SLAM with adding 4 gallons of LC.

You mentioned keeping the pump on 24/7. My current schedule is: 2800 RPM for 9 hours, 2200 RPM for 10 hours, 1800 RPM for 3 hours. I need to add 2 hours somewhere in there... maybe set the 1800 RPM mode for 5 hours overnight?
 
Update: I just redid a CYA test and now I can still see the black dot even filled up to 30 on the scale. See the attached picture. Does that mean CYA is 30? Or even lower?

Edit: also, PH is now 7.2, so I think I’m ready for SLAM - depending on the CYA question above.

1683057010327.jpeg
 
Last edited:
ugadawgs311 said:
See the attached picture.
Click to expand...
Remember = CYA testing should be done with certain parameters. From CYA Testing - Further Reading
As much as possible you should do the CYA test in the same consistent light conditions:
  • Outside in full sun or use the brightest indirect indoor light that you can if you have to test at night
  • Back to sun
  • Don't stare at the dot as you pour
  • Fill to a line, hold the tube waist high, and glance at the dot
  • If you see the dot fill to the next line and glance at the dot
  • When the dot disappears you round up to the previous line. If you saw the dot at 40 and not at 30 then you call it 40
 
  • Like
Reactions: Mdragger88 and ugadawgs311
mknauss said:
Remember = CYA testing should be done with certain parameters. From CYA Testing - Further Reading
As much as possible you should do the CYA test in the same consistent light conditions:
  • Outside in full sun or use the brightest indirect indoor light that you can if you have to test at night
  • Back to sun
  • Don't stare at the dot as you pour
  • Fill to a line, hold the tube waist high, and glance at the dot
  • If you see the dot fill to the next line and glance at the dot
  • When the dot disappears you round up to the previous line. If you saw the dot at 40 and not at 30 then you call it 40
Click to expand...
I did both tests in the same environment with the same lighting. The 2nd time however, I immediately filled to 40 then checked - still saw the dot. Next, filled to 30 - still barely saw the dot.

The only difference I can think of is I didn’t stare constantly at the dot during the 2nd test.

In this case, is my CYA be 30?
 
Remember, the CYA does not change in a short period of time (several months) unless you drain off alot of water and replace with fresh water or add CYA containing products. Have you done either of those things since your last test?
 

Enjoying this content?

Support TFP with a donation.

Give Support
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply