Adjusting Pentair Intellichlor IC40

[newpoolguy]

I live in NJ. This is the first season with our new pool. It's an inground pool that's 12'x30', approx. 8400 gals. I'm trying to adjust the Pentair Intelichlor 40 SWG. When the pool was opened for the season, it was shocked causing the chlorine to be off the charts. Per the users manual, I turn the unit of and waited for the Chlorine level to get to 2.0-4.0ppm. When it got to 3.3 I turned it back on and set the unit to 60%. after 24hrs. I measured again and Chlorine was 5.35 so I lowered the unit to 40%. After 48 hrs and no pool usage due to some cool weather, I measured it tonight and it's 8.1, so I lowered the unit to 20%. I'm going to wait another 24 hours and see if the Chlorine goes down. For the record, I'm running to pump from 10am to 6pm.

Am I doing these adjustments correctly? If I'm not please give me your advice. Should I change the length of time the pump is running? Should I run it at a different time of day?

Thanks for your help.

[PoolDoc]

Sounds like you are using a digital reader -- you've got more 'digits' in your results than any pool side test can legitimately deliver. Many times these units are massively inaccurate and can have you trying to correct bad test results.

So for starters, why don't you collect a big sample, bring it inside, split it into 3 parts. Test one, turn your unit off, wait 15 minutes, turn it on and test another and so on. Then list all THREE results here, so we can get an idea of how good (or bad) your testing is. Also test a tap water sample and then compare to your water companies average results (almost always online).

As far as the unit, your pool has got about the same surface area as a country club KP I have a IC40 on. My on-time usually sits at 20% with 24/7 pump run . . . or 5 hours per day of unit operation. For you, with 8 hours of run, that would be ~50% setting. But, you've got a lower load and (probably) much higher CYA. Splash out on the KP means my CYA rarely is more than 10 ppm.

So I'm guessing your unit needs to be lower.

I'd put it on 20% and let it go. Keep in mind that if you have several cloudy days, the chlorine will go too high.

BUT . . . without better test results and without knowing your CYA level this is all just WAG'ing (Wild A__ Guess). Check out my "Best Guess" chart below (no longer a guess, much less a WAG) and the Amazon links to the Taylor K2006 or 2006C -- which deliver a genuine 0.2ppm chlorine resolution.

Ben

[newpoolguy]

Took three FCl test tonight. These tests were done after my daughter was in the pool for about 1 hour. During the time she was in the pool, the pump was running, but the SWG was off.

Three tests are:

Test 1: 7.67
Test 2: 7.24
Test 3: 6.61
CYA: 62

[PoolDoc]

Yeah. That's pretty much what I expected.

At best, your ACTUAL chlorine reading is 7 ppm plus or minus 1. All those extra digits in you answers are bogus -- your test method can't distinguish 7 ppm from 6 ppm, much less 6.61 from 6.71 ppm.

But I'm not sure it's even that accurate. Please get a cheap OTO / phenol red kit. The OTO kit is not super accurate, but it is reliable. And see if you have have your CYA tested. There is NO method available to homeowners that can distinguish 60 ppm from 62 ppm. Most can't distinguish 60 ppm from 70 ppm.

But, assuming your do have 7 ppm Cl + 60 ppm CYA, your chlorine readings are reasonable and don't need 'fixing'.

Ben