Possible kind of algae growth?

[soundthisgarden]

8.0 Free Cl

TC 8.0 (no diff)

CC > 0.1

pH 7.4

TA 60

CH 225

CYA 40

Phosphates 1000 (Seaklear test strip)

Hello, I have been having issues with my 115 K gal outdoor plaster pool concerning a type of algae. I have not had time to SLAM yet and have shocked the pool twice within 2 weeks (16 hrs a piece) to no avail and immediate return of a coating on pool walls and floors that looks like algae. I just wanted to confirm from the community on here what exactly to do.
My situation is a little different with the outdoor pool because we have a flow rate problem that only reaches around 150 GPM, when it should be reaching min 300 GPM max 500 GPM. I have kept Cl and pH in check and I still have this algae problem. I have to approve any days of closure and I have this flow rate issue. Will doing SLAM work with a complex issue of a low flow rate pool? How many days should I ask for the pool to be closed while I SLAM do you guys think?

Attached are some images related to the look of the pool and the in the equipment I use. (Note the FC Reading in the controller is inaccurate due to low flow)

 

[kul]

You have algae and haven’t done a proper slam yet. Adding chlorine here and there won’t solve the issue. It’s hard to tell how long a slam is going to take until you get going. Have you done an OCLT test to see how much chlorine you’re losing?

SLAM Process
Overnight Chlorine Loss Test

 

[soundthisgarden]

I have not done an OCLT yet but plan to do it soon and post the results here. Thanks for the reply. I figured as much that I need to do a proper SLAM. I also need to purchase another test kit to do more tests for CC chlorine.

 

[PoolStored]

I’m not sure that you can SLAM your pool. As a commercial pool what are acceptable CYA levels?

 

[soundthisgarden]

I can have my CYA level at 30-50, but avoid any thing higher than that.

 

[PoolStored]

Great! Get a kit and slam on! Link—>Test Kits Compared

 

[soundthisgarden]

I’ll kit up and hopefully they’ll allow me a few days of closure so I can SLAM away. I’ll post updates as soon as I start.

 

[PoolStored]

At 115k G, you gonna need lots of liquid chlorine!

 

[PoolStored]

Is there a restriction on fc levels and swimmers?

 

[soundthisgarden]

Oh yeah! I’ve got plenty of brickets for the pulsar I use. I’ll look at getting a different liquid chlorine though if you guys recommend that.

 

[soundthisgarden]

Is there a restriction on fc levels and swimmers?

Yes, so I will most likely have to close for almost a week. I do have the indoor pool that people could still use though. So hopefully my management will be cool with that.

 

[PoolStored]

You are using cal-hypo system?

 

[soundthisgarden]

You are using cal-hypo system?

Yes

 

[PoolStored]

That is a different bird. Do you know what the max feed rate is? Need to ensure it is high enough to maintain SLAM level.

Cal-Hypo can be used to SLAM, but will cause cloudiness. Near the end, to ensure you have a clear pool and can see it, you will want to convert to liquid chlorine.

Back of the napkin, 30CYA, target SLAM level is going to be 12FC. You are at 8. Initial is 6lbs Cal-Hypo. Say you lose 2FC every 2 hours, daylight is about 10 hours, so 5 treatments per day, that is 15lbs per day. Full week SLAM would be 6+(15x7) = 111lbs. 111lbs will raise your CH by 53ppm. (These numbers are not a prediction, just to give me a ball park feel of the amount you *MIGHT* need to use and impact on CH) How do you manage CH levels when they get high?

 

[soundthisgarden]

It is still liquid, they are cal-hypo brickets that are watered down into liquid form and then pumped into pool. Should have clarified earlier my bad. Thank you for the ballpark info! My CH is managed by adding the calcium hardness granules in diluted water after thoroughly mixing to raise CH, and I can fill the pool with new water and backwash to lower CH.

 

[soundthisgarden]

It is still liquid, they are cal-hypo brickets that are watered down into liquid form and then pumped into pool. Should have clarified earlier my bad. Thank you for the ballpark info! My CH is managed by adding the calcium hardness granules in diluted water after thoroughly mixing to raise CH, and I can fill the pool with new water and backwash to lower CH.

The rate is set to constant feeding every 2minutes even when there are no brickets in the bucket to get soaked.

 

[PoolStored]

It is still liquid

I get it. You need to know the max rate. You will likely want to up the rate to keep the FC at 12. You need know what the max rate is to ensure you can flow enough to maintain the 12 FC...

 

[PoolStored]

Said another way, can you get 3lb of product (dry) into the pool every 2 hours? (I'm assuming that you will get a 2fc loss every 2 hours at the beginning. It may be higher or lower). Again, just back of the napkin. If you can't 3lbs in 2 hours, then you may need to supplement with LC to maintain target FC for SLAM.

 

[soundthisgarden]

Here is the specs: the max rate is 189lbs a day for the Pulsar Precision.

 

[soundthisgarden]

Said another way, can you get 3lb of product (dry) into the pool every 2 hours? (I'm assuming that you will get a 2fc loss every 2 hours at the beginning. It may be higher or lower). Again, just back of the napkin. If you can't 3lbs in 2 hours, then you may need to supplement with LC to maintain target FC for SLAM.

Yes it can easily eat up and send 3 lbs in 2 hrs. Thank you for the clarifications. You’ve been quite clear and helpful.