About to embark on a SLAM....

Kalico

Bronze Supporter
May 29, 2021
49
San Martin, CA, USA
Pool Size
22000
Surface
Plaster
Chlorine
Liquid Chlorine
Hello new friends. I am so grateful for the help already received and have been learning a lot! I posted previously that I was just getting started on a new (old) pool that came with black algae and developed green algae. I was waiting on a Taylor K-2006 test kit to arrive next weekend, and it arrived today!!! So I have tested my water, logged it in PoolMath, and I think a link to that information will show up now...somewhere?

After reading Pool School for a day, I figured I would find high CYA and low FC....since the previous homeowners were primarily using tablets and just throwing in a packet of shock once a week. And we were just doing what they told us...until it turned green. (We didn't even know about black algae at the time; we just figured that the pool needed to be refinished!)

So here's what my new test kit tells me:

FC - 2.8
pH - 7.8
TA - 90
CH - 700
CYA - 100
CSI - .37
TEMP - 76 (pool is not heated)

So here's what I've gathered are the next things to do in the order I think I should do them (corrections welcome!).
  • Fill+drain to reduce the CYA to 30-40. (How often should I check CYA during fill+drain?)
    • Scrub the black algae with a steel brush.
    • Clean the cartridge filters.
  • Lower the pH to 7.2-7.5.
  • Start SLAM.
    • Continue to scrub the black algae and brush the pool daily.
Does that sound right? Missing anything?

TIA 🌻
 

wireform

Silver Supporter
In The Industry
Aug 15, 2017
2,542
Spring Valley, NY
Kalico,
You got off to a good start by getting a recommended test kit. Your CYA is 100 but may be higher then that albeit the test is maxed out @100 so therefore do a diluted CYA test to see what you get and double your results to get the definitive CYA total. Once you know the CYA you'll need to drain X amount plus a bit to be sure you achieved lowering the CYA to X. No, you can't check while drain or exchange the water since it needs to be mixed up by way of the pump and you wouldn't want to disturb the exchange if that's the route you go with. After you have the CYA to the manageable level you'd do the slam and roll from that point.
I'll let the experts guide you if draining is even an option as it can be risky with ground water popping the pool shell out of the ground......
 

Kalico

Bronze Supporter
May 29, 2021
49
San Martin, CA, USA
Pool Size
22000
Surface
Plaster
Chlorine
Liquid Chlorine
Thanks @wireform! I was advised in a previous post to check with the county and/or local pool builders to find out about the water table issue (drain, pop) and I haven't found any good information yet....but I will try to make some phone calls next week.

We live in a very dry area and the pool is about 50' away from a dry creek bed which is deeper than the pool itself. So I have a pretty good idea that the water table is lower than the pool, but I'll be sure before I decide to drain it. Given that there is any worry about this at all, I was planning more on doing an "even exchange" rather than draining...unless the only option to get rid of the black algae turns out to be draining (at least to the point where it is easy to work on). But....from all I've read here, it sounds like it's possible to attack black algae without draining so I am hopeful.

Considering what you said about checking CYA levels, I think I need to understand more about how to exchange water. We have an external pump that allows us to drain water into the creek bed. So I am pretty sure we can drain and fill simultaneously. I think this will also keep the water mixing, since it will be in motion all the time. But turning off the filter makes solid sense, to ensure that we never get the water too low and burn out the pump. Anything else I need to know?
 

wireform

Silver Supporter
In The Industry
Aug 15, 2017
2,542
Spring Valley, NY
Read This for more on draining. Draining by exchange is a method of replenishing the water at the same rate you're removing it. One is in the deep end while the other is in the shallow and depending which of the two are colder will determine what goes where. You don't want to mix while exchanging as the water temperatures are different one stays at the bottom and one remains at the top. Pump stays OFF the whole time. Easiest would be drain and refill but that all depends on the water table.
 

Kalico

Bronze Supporter
May 29, 2021
49
San Martin, CA, USA
Pool Size
22000
Surface
Plaster
Chlorine
Liquid Chlorine
Edit: removed the entire post. I have begun to realize that the questions I was asking needed more clarity and more context, so I posted fresh in the "Deep End" forum: Replacing water...confuzzled!

Thanks for all the help here! :lovetfp:
 
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