Pool continues to have algae / green sediment on the bottom

Stevenover

Member
May 20, 2021
5
Alberta
I have a new steel wall pool with a vinyl liner inside a greenhouse. We used it since May and have used a combination of Trichlor and Bleach. Total of 3200 grams of Trichlor. PoolMath says for a 45000 L pool it should have a CYA level of 39. The water stayed perfectly clear. I was very busy for 2 weeks 2 months ago and was not able to test every day. I had been maintaining it at 2-4 ppm chlorine. Some extra people were swimming in the pool as well. I noticed some green coloration to the water about 6 weeks ago. I added 11.2 L of 10.8% bleach to shock the pool August 16-19. Vacuumed it several times and then noticed it was green again. I added 3.6 L of 10.8% bleach on August 28 and 14.4 L of 10.8% bleach on September 7. I estimated over 48 ppm of Chlorine at that time since it started at 8 ppm. I checked the CYA level with my kit but it was not that clear what the level was. It should be a little less than 39 because I added 1000 L of water at least 3 or 4 times. Since then the chlorine level has slowly been coming down. It is at 8 today. I still need to vacuum it every few days and the bottom looks just as green as before. The pH is at 7.6, the temperature is 22-24 C. Is there something else I can do? My alkalinity is always a little high at 180 but before the algae came into the pool it was clear for 3.5 months with kids swimming in it every day. My pool came with numerous chemicals, algicides and clarifiers and non-chlorine shock. I have not used any of them and it was working very well. Any ideas for what to do next. I would like to put it up for the winter in good condition.
 

Attachments

  • IMG_9551.JPG
    IMG_9551.JPG
    485.8 KB · Views: 22

Bperry

Gold Supporter
Aug 20, 2020
990
Knoxville, TN
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
I have a new steel wall pool with a vinyl liner inside a greenhouse. We used it since May and have used a combination of Trichlor and Bleach. Total of 3200 grams of Trichlor. PoolMath says for a 45000 L pool it should have a CYA level of 39. The water stayed perfectly clear. I was very busy for 2 weeks 2 months ago and was not able to test every day. I had been maintaining it at 2-4 ppm chlorine. Some extra people were swimming in the pool as well. I noticed some green coloration to the water about 6 weeks ago. I added 11.2 L of 10.8% bleach to shock the pool August 16-19. Vacuumed it several times and then noticed it was green again. I added 3.6 L of 10.8% bleach on August 28 and 14.4 L of 10.8% bleach on September 7. I estimated over 48 ppm of Chlorine at that time since it started at 8 ppm. I checked the CYA level with my kit but it was not that clear what the level was. It should be a little less than 39 because I added 1000 L of water at least 3 or 4 times. Since then the chlorine level has slowly been coming down. It is at 8 today. I still need to vacuum it every few days and the bottom looks just as green as before. The pH is at 7.6, the temperature is 22-24 C. Is there something else I can do? My alkalinity is always a little high at 180 but before the algae came into the pool it was clear for 3.5 months with kids swimming in it every day. My pool came with numerous chemicals, algicides and clarifiers and non-chlorine shock. I have not used any of them and it was working very well. Any ideas for what to do next. I would like to put it up for the winter in good condition.
What is your CYA level? If you’ve been using trichlor it’s probably too high. And if your FC level has really been at 2-4ppm, then that’s why there’s algae. Take a look at the pool school articles for the SLAM process and follow that.
 

revitup

Gold Supporter
Bronze Supporter
Nov 30, 2019
645
Pawleys Island, SC
Pool Size
8500
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Let’s start with
“PoolMath says for a 45000 L pool it should have a CYA level of 39.”
Where does Poolmath tell you that?
 

Stevenover

Member
May 20, 2021
5
Alberta
I added 3200 grams of Trichlor over the past few months. If you check the effects of adding 3200 grams of Trichlor to a 45000 L pool on PoolMath it says it will raise the CYA level to 39. I think it may be little lower because when I try check it with my testing kit the level is not that clear. I added a 1000 L of water 3 or 4 times which would make it a little lower as well. The only thing I have not done in the SLAM protocol is bring the pH down below 7.5. It is always at 7.6 except just after I add a lot bleach. The highest it climbs then is 7.8, but goes down to 7.6 without the addition of any more chemical.
 

Mike1162

Silver Supporter
Jun 13, 2015
1,103
N Tonawanda, NY
If your CYA is really 39 (should be tested) then you should be maintaining FC between 5 - 7 ppm.
What test kit are you using?
Are you brushing the pool?
You should start a SLAM asap.
 

Bperry

Gold Supporter
Aug 20, 2020
990
Knoxville, TN
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
I added 3200 grams of Trichlor over the past few months. If you check the effects of adding 3200 grams of Trichlor to a 45000 L pool on PoolMath it says it will raise the CYA level to 39. I think it may be little lower because when I try check it with my testing kit the level is not that clear. I added a 1000 L of water 3 or 4 times which would make it a little lower as well. The only thing I have not done in the SLAM protocol is bring the pH down below 7.5. It is always at 7.6 except just after I add a lot bleach. The highest it climbs then is 7.8, but goes down to 7.6 without the addition of any more chemical.
You should read the SLAM protocol again as it sounds like there’s some confusion on what that is. It requires you to test the water and record the results after adding chlorine to make sure you reached the level you expected. So far you haven’t posted any water test results so it’s pretty hard to give any useful advice other than you need more chlorine if it’s green.
 

Stevenover

Member
May 20, 2021
5
Alberta
Thank you all. My ph was 7.6, FC 5.5 and CC 0 and CYA 50 (higher than I thought it would be) this morning. I added enough acid to drop the pH to 7.2 and added enough chlorine bleach to increase levels to 21 ppm. I will keep testing to ensure it stays there and will keep the pump on. I will let you know how it works.
 

Bperry

Gold Supporter
Aug 20, 2020
990
Knoxville, TN
Pool Size
27000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
CircuPool RJ-60
Thank you all. My ph was 7.6, FC 5.5 and CC 0 and CYA 50 (higher than I thought it would be) this morning. I added enough acid to drop the pH to 7.2 and added enough chlorine bleach to increase levels to 21 ppm. I will keep testing to ensure it stays there and will keep the pump on. I will let you know how it works.
Make sure to test it 3-4 times per day if possible to make sure it stays up there.
 

Stevenover

Member
May 20, 2021
5
Alberta
I don’t know if I read this anywhere but do you leave the pump off for the overnight chlorine test? It seems that if the pump is on and the pool is uncovered that some chlorine would be lost to evaporation.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,321
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Chlorine is not lost to evaporation. FC is reduced by UV impact and organics. Overnight there is no UV. If no organics, your FC loss overnight should be zero.

You should leave the pump on if possible. If not, it should be on for 30 minutes prior to taking the morning water sample for testing. The cover can be on or off.
 

Enjoying this content?

Support TFP with a donation.

Give Support

Stevenover

Member
May 20, 2021
5
Alberta
Chlorine is not lost to evaporation. FC is reduced by UV impact and organics. Overnight there is no UV. If no organics, your FC loss overnight should be zero.

You should leave the pump on if possible. If not, it should be on for 30 minutes prior to taking the morning water sample for testing. The cover can be on or off.
Thank you. The reading this morning was 16 so it appears to have lost 4 ppm overnight. The pool looks very clean. I will keep it up.