High CYA-Need to SLAM

[Mechanicman]

I have finally convinced our cousin to get rid of his pool "service" and join the TFP way. Pool was completed and filled September of 2020. He has used a pool guy from day one that has been keeping the tablet feeder full. Currently has algae in the pool and I have convinced him to switch to a SWG. He is getting ready to place his order for the IC60 and power center to go along with his intellicenter. I know we need to do a SLAM with liquid chlorine to address the algae, which doesn't make sense to do with his CYA where it is. His current CYA reading is 140-160 (obtained by diluting pool water 50/50 and multiplying result by 2). At 70 you can barely make out the black dot and at 80 you can not make it out at all. His CH is also really high. I am thinking we need to drain about 50% of the pool and refill to get the CYA and calcium down to where it should be. CH of fill water is 250.

My question is, would draining 50% be enough? He is on a well so we don't want to drain more than we need to but we also don't want to have to keep draining and refilling. I have posted a complete set of his test results.

 

[Texas Splash]

My question is, would draining 50% be enough?

Hard to tell. It will still be a bit elevated, but much better than what it is now. But since he will need to run a SLAM Process, it would be ideal to get the CYA down to about 50 so that he can maintain a lower FC SLAM level. You won't know until you do the first exchange. Then you can decide if you want to do another partial exchange or just press-on.

 

[Mechanicman]

Water can’t be delivered until Friday or Saturday so we need to wait a few days to drain. Should I add chlorine to help slow the algae or just wait until we drain and refill and SLAM?

 

[MITBeta]

Add 5ppm of chlorine per day until you exchange.

 

[Rancho Cost-a-Lotta]

Which "fill water" has a CH of 250; the trucked-in water or daily top-off water? If he plans to top-off with CH 250 water, you want to get CH down to the lower end of the acceptable range unless he has access to softened water.

 

[Mechanicman]

That is the CH of his fill water. I know he has a water softener but based on that test result I don't think this hose bib is going through the softener. I do have to admit the CH test is hardest for me, but I think I am getting better of getting the baby blue and not purple.

 

[Rancho Cost-a-Lotta]

That is the CH of his fill water. I know he has a water softener but based on that test result I don't think this hose bib is going through the softener. I do have to admit the CH test is hardest for me, but I think I am getting better of getting the baby blue and not purple.

If you can convince him to hook up the softener to his fill line, he may never have to drain/refill again. His current fill water will require him to exchange water in one to two seasons.

Not knowing the CH of the trucked-in water, it's tough to calculate how much water needs to be exchanged.

For the CH test, don't worry so much about the color. Continue with drops until there is no color change, then deduct that last drop.

Nice of you to help out your cousin. Sounds like he's making some good decisions. I hope all goes well.

 

[crusemm]

a 50% dilution will get his CYA down to 70-80, any lower will require more dilution. To get to 50 will require approximately 60-65% dilution

 

[Mechanicman]

For the CH test, don't worry so much about the color. Continue with drops until there is no color change, then deduct that last drop.

Nice of you to help out your cousin. Sounds like he's making some good decisions. I hope all goes well.

I have a hard time watching the color change in the CH test. Seems so minor to me. All the other ones are very obvious when there is change.

Took a while to convince him the pool guys weren’t doing him any favors! This last algae outbreak he finally let me bring my test kit over.

 

[Mechanicman]

I just wanted to post an update to give other people hope and confidence that the SLAM procedure really does work!! The first three photos are before we started on 4/18. We drained approx 50% of the pool and refilled it due to the high CYA and CH. 4/19 I dropped the pH to 7.2 and added chlorine on the morning of 4/20. I checked and adjusted chlorine three times on 4/20, twice daily until Sunday 4/24. On Sunday we passed the OCLT. I would brush the pool any time I tested and added. The filter was on 24/7 as well as the cleaner and spillway. The fourth picture was from the afternoon of 4/21. The fifth picture is yesterday morning. Finally the last two were last night after the wind died down.

This was my first SLAM so I was a bit nervous but I followed the procedure and it turned out great. I installed the SWG earlier today so they should not have to go through this again! I am thanful for everything I have learned here. We ended up using approx 18 gallons of chlorine. Their pool is approx 30,000 gallons.

 

[Texas Splash]

Outstanding!

 

[Newdude]