Damaged pool cover edge collecting algae

[stroud_pool_owner]

I would be grateful for help with green algae. Small amounts have appeared along the grout of the floor of the deep end of the pool.
I keep the FC (90% of the time) at 3-5 ppm.
The pool water is clear.
The pump runs for 4 hours each day.
I have a thermal insulation cover made of 600 micron geobubble. The edges are not sealed so many of the exposed bubbles have algae growing in them. This is not helped by the edge of the cover becoming frayed as it rubs against the pool edge as it is wound out of the pool.

Is SLAMming the pool needed to get rid of the algae on the floor of the pool?
Should I trim the edge of the cover to remove the rough edges?
Is there anything I should do on a regular basis to stop the algae growing in the exposed bubbles of the cover?

Thank you for all your advice.

 

[Bperry]

I would be grateful for help with green algae. Small amounts have appeared along the grout of the floor of the deep end of the pool.
I keep the FC (90% of the time) at 3-5 ppm.
The pool water is clear.
The pump runs for 4 hours each day.
I have a thermal insulation cover made of 600 micron geobubble. The edges are not sealed so many of the exposed bubbles have algae growing in them. This is not helped by the edge of the cover becoming frayed as it rubs against the pool edge as it is wound out of the pool.

Is SLAMming the pool needed to get rid of the algae on the floor of the pool?
Should I trim the edge of the cover to remove the rough edges?
Is there anything I should do on a regular basis to stop the algae growing in the exposed bubbles of the cover?

Thank you for all your advice.

SLAM is always needed when there’s visible algae. But the question you might try to answer first is how did it get there? If you run the FC at 3-5ppm what is the CYA level? The CYA level is what drives the proper amount of FC. Have a look through the CYA/FC chart to check it out. Free Chlorine and Cyanuric Acid Relationship Explained

 

[Newdude]

+1. There is no reasonable way to cut a solar cover and not have half of the bubbles exposed. Every cover in the land has similar.

If algae is growing, its because you're letting algae grow, not because of the bubbles.

 

[stroud_pool_owner]

Thank you both for your advice. I haven't checked the CYA for about 4 years. It was 60 then. I haven't used anything other than liquid chlorine since 2016 so I figured it wasn't going to change much.
More significantly I hadn't tested anything other than the free chlorine since 2018 as the pH and TA stayed constant at 7.6 and 100. However today they are 8.2 and 250. So that probably explains why the chlorine was not working adequately.
So, I have scrubbed the pool bottom, added 2.8kg of dry acid (to get to 7.3) and 1.4l of 14% liquid chlorine (to get to 7ppm), vaccuumed the pool, left the pump running and I will check the FC tomorrow.
Incidentally, would you recommend I leave the pool solar cover off while I am doing this, or extend it over the pool so the pockets of algae in the exposed bubbles get the full force of 7ppm of chlorine?
Thanks again for your advice.

 

[stroud_pool_owner]

I have just realised I need to get the chlorine up to 24ppm for the SLAM process if my CYA is 60. I will get the CYA checked tomorrow as it may now be lower than it was in 2019(!)- it is not possible to get the recommended testing kit in the UK so I have to take a water sample to the local pool maintenance company.

 

[Newdude]

I will get the CYA checked tomorrow as it may now be lower than it was in 2019(!)

It degrades a couple ppm a month, and in the places with more rain than evaporation, it loses a couple more ppm monthly due to draining. Filling after backwashing removes more and unless you've added it without realizing it, you've been at 0 for a couple years.

 

[Mdragger88]

As for the cover- cut off the offending bubbles & give the whole thing a good bleach soak

 

[stroud_pool_owner]

As predicted by @Newdude the results are back from the pool store. CYA level is 0. The CYA calculator at Free Chlorine and Cyanuric Acid Relationship Explained does not offer the option for a CYA of 0. But for CYA 20 it advises a FC level of 10. Which is what I used to calculate the chlorine dose last night. And this morning it looks like the FC level is no more than 1ppm down.
Regarding the CYA level, I know it is important in reducing UV consumption of the FC. However as I have a clear polycarbonate dome over the pool, and the manufacturer assures me that this is a UV screen (and my grandchildren have never shown evidence of sunburn after swimming with no sunblock) I figure that I don't need CYA. This will mean I can run FC levels around 3-5 safely. What are expert's views on this please?
What I have learnt is that I need to check the pH more often than every 3 years!
And now I'll get on with chlorine soaking the pool thermal cover...
Thanks again for your collective advice.

 

[Bperry]

As predicted by @Newdude the results are back from the pool store. CYA level is 0. The CYA calculator at Free Chlorine and Cyanuric Acid Relationship Explained does not offer the option for a CYA of 0. But for CYA 20 it advises a FC level of 10. Which is what I used to calculate the chlorine dose last night. And this morning it looks like the FC level is no more than 1ppm down.
Regarding the CYA level, I know it is important in reducing UV consumption of the FC. However as I have a clear polycarbonate dome over the pool, and the manufacturer assures me that this is a UV screen (and my grandchildren have never shown evidence of sunburn after swimming with no sunblock) I figure that I don't need CYA. This will mean I can run FC levels around 3-5 safely. What are expert's views on this please?
What I have learnt is that I need to check the pH more often than every 3 years!
And now I'll get on with chlorine soaking the pool thermal cover...
Thanks again for your collective advice.

FC of 5ppm is really harsh without stabilizer. Indoor pools are still recommended to have 20-30ppm CYA to buffer the harshness of chlorine. You’ll get the same advice in this case, even IF chlorine ONLY breaks down with UV light and IF your dome blocks 100% of UV light. (There’s a big difference between an unqualified “UV screen” and “blocks 100% of UV light.”) A tree is also a UV screen.

That’s a lot of IF’s. The issue is that chlorine doesn’t only degrade from UV light. It also degrades in heat and time. Chlorine in the bottle degrades over time even if it’s indoors and in air conditioned environment.

 

[Mdragger88]

Great news on the Overnight Chlorine Loss Test
Aim for 20-30ppm cya for the reasons @Bperry mentioned.
& aim for target fc for that cya
FC/CYA Levels

 

[stroud_pool_owner]

Thank you for your collective wisdom. I'm going away for 10 days soon so I'll get some solid chlorine blocks (Swimming Pool Large Chlorine Tablets 1kg) to boost the CYA level up to 20-30 ppm and provide sufficient chlorine while I'm away.
Thanks again, really helpful advice.

 

[Mdragger88]

Watch your ph as trichlor is acidic.
It says each one is 200 grams

 

[stroud_pool_owner]

Thank you @Mdragger88 that is a good point about the pH. I will need to use 7 tablets to get the CYA up to around 20 and that will have a significant effect on the pH.
It looks like I will have to get a tub of CYA. No sign of algae though so that's a win.

 

[Mdragger88]

Thank you @Mdragger88 that is a good point about the pH. I will need to use 7 tablets to get the CYA up to around 20 and that will have a significant effect on the pH.
It looks like I will have to get a tub of CYA. No sign of algae though so that's a win.

It won’t all happen at once since they take some time to dissolve just be sure that you don’t also dose with acid to lower ph without taking that into consideration.

 

[stroud_pool_owner]

It seems to be taking a lot of acid to correct the TA. I have put in about 4kg of pH-. The pH is down from 8.2 to 7.6. I have a home made aerator going 12 hours per day. But the TA is stuck on 200. Keep going with the pH- I guess.

 

[Bperry]

It seems to be taking a lot of acid to correct the TA. I have put in about 4kg of pH-. The pH is down from 8.2 to 7.6. I have a home made aerator going 12 hours per day. But the TA is stuck on 200. Keep going with the pH- I guess.

No access to muriatic acid? The dry acid has sulphates which will damage equipment as if builds up. Try and avoid it if you can.

 

[Mdragger88]

Pro tip- if its hot there & you also want to keep the pool cool point the holes up so you get a fountain effect & evaporative cooling while you’re aerating.
Like this

It’s also fun for the kiddos & adults too!

 

[stroud_pool_owner]

No access to muriatic acid? The dry acid has sulphates which will damage equipment as if builds up. Try and avoid it if you can.

I think this is another frustrating issue with pool care in the UK. Muriatic acid is not easy to come by and isn't available from pool stores on line. However it is available from industrial chemical providers so I will try to get hold of it from them.
Thank you very much for this advice.

 

[stroud_pool_owner]

Pro tip- if its hot there & you also want to keep the pool cool point the holes up so you get a fountain effect & evaporative cooling while you’re aerating.
Like this View attachment 523905
View attachment 523906
It’s also fun for the kiddos & adults too!

Thank you for this advice. Forgive the wry smile. Here in England we are not blessed with extended periods of warmth. My pool temp has not been higher than the daily peak temp for all but about seven days this summer!