First Spring with a SWCG (repeated from another thread)

I may have place my initial question on the wrong forum, so I thought I would repeat my request as related to pool water chemistry instead of a question concerning SWCG systems. My question is as follows:

I had a Pentair IC40 installed in July of 2014 and it has worked without too many issues. However, now it is spring in southwest Georgia and I have been told by my granddaughter that she and her friends are ready to swim.

I had previously used the BBB method of pool maintenance and I would now like to know what the proper ranges are for pool chemistry now that I have a SWCG system.

As of my last check this morning ....pH 7.4, FC 2.2, ALK 90, CYA 55 and salt 2500. I have a 25000 gallon pool, well water with vinyl liner. The pool at present has some green algae and I just about have all the organic matter cleaned out.

Any help would be most appreciated.

jhk49

What test kit are you using? I believe the pentair requires around 3000-3200ppm salt, no?

Before you bump up the salt, please measure it using either AquaChek test strips or a Taylor K-1766 test drops. The Pentair salt level output is not temperature compensated and is typical +/- 400ppm. Unless you know the exact history of salt additions to the water, it's hard to know what your salt level is exactly. Both of the aforementioned test methods are typically +/- 200ppm so they will get you in the right ball park. I only use the salt level output on the IC-40 as a proxy check for a properly operating cell, not for an exact value. For reference, my salt is on the high side (~4000ppm measured by Taylor K-1766) and my IC40 is fine.

Others may disagree, but I keep my CYA on the high side at 70ppm. Your SWCG creates lots of bubbling and mixing during operation and it is possible on short pipe runs for not all of the chlorine gas generated to be absorbed. Higher CYA values help that. Also, higher CYA values have a slightly better UV protective effect which will let you run the IC40 on lower power. I know when my CYA is down at 50ppm, I have to run my IC40 at 50% to keep my FC up. However, when I keep the CYA 70ppm, I can lower to cell output to 30-35% and still keep the FC in the right ranges. That extra 15-20% translates into longer cell life.

Since you're on well water, try to get a measure of metal levels (iron and copper). Other than shock cleaning the pool to kill your green algae, I'd say your other values look ok. Do your shock process with the CYA low and then raise it slowly over time. You can either use granular pool conditioner (100% cyanuric acid) or you can use 3" pucks in a floater. Just raise it slowly because it takes a long time (~1 week) for CYA to register on tests.

Also, please use a Taylor K-2006 test kit to measure your water. Pool store testing is inadequate (except perhaps for metals) and multi-point test strips are typically too inaccurate. And ignore all advice pool stores give you on chemical additions, they are just trying to sell you junk that you do not need.

The Intellichlor manual lists all of these values for you on page 10.

The manual can be found here

For easy reference:
http://i28.photobucket.com/albums/c2...psm38jpakh.png

I don't think you really need to worry about TDS, nitrates, phosphates.

So you'll need about 188lbs (4-5 40# bags) more salt... Add it slowly, not all at once. Also make sure the SWCG is OFF while adding salt and for about a day afterward. If you don't turn the cell off, the increased salinity can potentially damage the salt cell by allowing more current to flow through the plates than the system is designed for.

I agree with SunnyOptimism. With SWCG, higher CYA is usually better. My aquarite reccomends 80 and I keep it at 80-90. Yours recommends 50-80 and I'd go with 80 if I were you. That's about 5# of CYA granules. Add this slowly through the skimmer. Maybe 1# a day and retest. CYA is easy to add but can only be removed through dilution.


As for the green algae. Don't bother turning on the SWCG until you've got it cleaned up. Shock with liquid chlorine. Do this before you adjust CYA. To shock with a CYA of 50 you need at LEAST 15ppm FC. You'd probably be fine taking it up to 20. Check and add chlorine a few times a day until it looks clear and you get 0-0.5 CC and you lose less than 1ppm FC from sundown to sunup (to take chlorine loss due to sun exposure out of the equation).

Here's the chart that tells you what levels of FC you use for shocking. http://www.poolsolutions.com/gd/best...ine-chart.html It's based on your stabilizer (CYA) level.

Yeah, that's standard Pentair IntelliChlor boiler-plate. They updated it a bit as my older manual says the CYA should be no more than 50ppm. And I love how they say to use Super Chlorinate mode to remove CC's...don't waste your time and electricity as SuperChlorination does very little. All it does is run your IC for 24hrs straight at 100% power. The net effect is only a minor rise in FC and MAJOR wear and tear on the cell plates. Better to remove CC's by simple bleach chlorination at shock levels. As for phosphates, it is remotely possible that you can form calcium phosphate precipitations if the phosphates levels are ridiculously high BUT the water chemistry has to be so far out of balance that other problems will manifest themselves way before calcium phosphate scale ever becomes an issue.

So I agree with @kelemvor except that I add powdered stabilizer (CYA) by placing 1 pound of it (16oz) into a nylon skimmer sock and tie off the top. Then I either hang the sock in front of a return, float it in a blue chlorine puck floater or put it in the skimmer basket. That way it can dissolve slowly and not clogged anything up. Also, powdered stabilizer is very acidic and will lower your TA so if you do use the sock method in the skimmer, only do so while the pump is running. If the pump is off, remove the sock from the skimmer and put it in a float. You do not want a large amount of CYA sitting in a small volume of water.