New Salt System, algae is recurring regularly

[jhk49]

In the past I have been a firm believer in the PoolForum, have used it often and have been a contributor. Previously I was using a BBB method and did not have problems. However, I have recently had a salt system installed as I was going to be away on vacation for some time and did not want my helpful neighbor to be in charge of adding bleach everyday.

Since the installation of the salt system, I have had a problem with keeping green algae out of my pool. The IntellChlor salt system is set at 40% and my chlorine levels maintain themselves at about 7.0. I have tried the next lower setting, i.e.. 20% and the chlorine levels drop to about 2.8. The other problem that I seem to be facing is that my pH often tends to go up faster than it once did. I have adjusted with muriatic acid based on the pool calculator website but it continues to trend up faster than I would think it should. Unfortunately, I do not have a test kit for how much salt is in the pool ..... all I know is that 13 bags were added for start up about 2 months ago.

My particulars are as follows:

I live in southwest Georgia
25,000 gal pool, vinyl liner
well water fed
reading as of today, pH 7.7, FC 7.0, ALK 80
salt system on 40%

My pool is located with several trees nearby, I continue to clean out leaves, sticks, bugs and frogs from my skimmer and the polaris bag at least once every 3 days or so.

When using the BBB method, I had no problems with algae unless I didn't tend to adding bleach regularly. I had thought the salt system would provide for that regular addition of chlorine without the work for me.

Does anyone have a suggestion on how to get this pool to maintain itself free of algae for at least a week without me having to watch it everyday.

Jim K.
Leesburg, GA

[Watermom]

What is your CYA reading?

[SunnyOptimism]

One of the problems you are going to run into with the IC40 fr Pentair (I own one too) is that if it is not matched with a Pentair control system, like the IntelliTouch panel, then the only output control you have is on the cell itself. The Pentair cell only allows for output control in increments of 20% which is often way too course for doing fine FC adjustments. As you noted, if you set it to 40%, your FC is too high (possibly, depends on your CYA level) and if you go to 20%, your FC is too low.

@Watermom nailed it - you need to start by measuring your CYA level first and then that will tell you what your FC level should be.

Also, once an algae bloom starts, a SWCG is useless in fighting algae. This is true for ALL SWCG! I know all the sales literature talks about "BOOST Mode" and "Superchlorination" but that's all sales mumbo-jumbo. Once you get an algae bloom, you have to fight it the good old fashion way with lots of bleach, maintenance of shock level FC and patient measuring each day to ensure that you're maintaining enough FC to kill the algae.

So, here's the prescription -

1) Figure out what your CYA level is. This will then tell you your daily target FC level and what your shock level is
2) Use the standard BBB approach to killing off an algae bloom - SHaPE (Shock, Hold and Persistently Evaluate...I know, it's a stupid acronym). Get your water up to shock level, hold it until all the algae is dead and clean your pool thoroughly.
3) Once your pool is clean of algae, start adjusting SWCG output percentage and pump run times to get the FC you need. You might try 40% for 8 hours per day run time and see what that gets you.

Good luck and keep posting results...

[EDIT]

As for rising pH, that is very common with SWCG pools. The SWCG cell produces chlorine gas which eventually dissolves and forms hypochlorite/hypochlorous acid. The process of producing chlorine is very alkaline. Eventually the pH rise is neutralized by the acidic reactions that occur when chlorine kills stuff or oxidizes organics, but initially the pH rises. So yes, you will need to add more acid than you did previously to combat the pH rise. There are other methods for alleviating the pH rise, but that is not at all the most urgent priority right now. Cleaning up your pool's algae bloom is the most important.

[END-EDIT]

[CarlD]

With an SWCG, the FC level must be at least 5% of the CYA level to MAINTAIN sanitation.

The BBB method and an SWCG are NOT different systems. BBB is a methodology, a system YOU practice.
SWCG is simply a way to introduce chlorine into your pool, continuously. No more than that.

You should be always using the BBB method. BBB stands for "Bleach, Borax and Baking Soda" but that's really only a quickie shorthand for the principle of testing your water religiously, and adjusting it as it needs it. Daily simple Chlorine and pH testing lets you get ahead and stay ahead of problems. An SWCG can make it so you don't have to do so much, but it's just making it easier.

But now you have algae so you should either turn the SWCG off or pretend it's not there, and use plain old bleach or liquid chlorine to dose your pool up to the shock level indicated for your CYA level, and keep the FC level there, testing 2-3 times a day, and adding bleach/liquid chlorine to raise it.

Let's get the algae killed first, then worry about the pH, and finally, after that, adjusting your SWCG to be optimal.

[jhk49]

Well, I certainly learned somethings today. I didn't realize that you could go back to bleach once you had gone to a salt system. The CYA is presently at 32. What level of chlorine should I reach to shock the pool and for how long do I need to hold it?

As suggested, I will get the algae bloom taken care of and then address the output level of the salt system. I am presently running the pool pump at the summer time levels of 10 hours per day. I think I can drop it to 6 hours per day and provide a FC range of 3.0 to 6.0.

Thanks for the continue support.

Jim Kempf
Leesburg, GA

As my Pennsylvania Dutch Grandmother would say, "Too soon we get old, Too late we get schmart."

[CarlD]

There's a lot to learn, Jim, but it's not really all that tough.

Pool care (water maintenance) comes down to 2 1/2 things:
1) Sanitation: That's chlorine to kill pathogens and break down bio matter
2) pH: How acidic or alkaline your water is.
2 1/2) Stabilizer to determine the proper level of chlorine.

Total alkalinity is mainly a buffer for pH, once you've eliminated obvious causes for its rise or fall. After that, if pH is rising too much, you generally lower TA. If pH trends down, you raise TA.
Calcium Hardness is useless in vinyl pools unless it's too high, then scaling can happen. In masonry pools (concrete, tile, etc) sufficient calcium in the water helps keep the calcium from leeching out of the walls.

For correct stabilizer levels, see the "Best Guess" table:
http://www.poolsolutions.com/gd/best...ine-chart.html

Not sure how you got a CYA # of "32". I presume you either got it from a pool store or guessed at it.

Normally, for a CYA of 30 to 50, we suggest a shocking level of 15ppm for your FC (free chlorine), and, generally, a maintenance level of 3-6ppm.

But you have an SWCG system and those usually require a CYA level of 60 to 80ppm. Correspondingly, with an SWCG, an FC level of at least 5% is recommended, which would be 3 to 4. But you CAN go higher if you need to. I generally do.

BTW, I use the BBB method and have an SWCG--an Autopilot. Remember: SWCG stands for salt water CHLORINE generation, and in your pool, chlorine is chlorine. All of us who have SWCGs occasionally supplement with other chlorine forms, but most usually bleach/liquid chlorine.