Converted to Salt system


Jun 9, 2008
Hi Everybody. I'm new to this great forum and as a result of reading everything here I have converted to a salt system. I've learned a lot but am now having pools problems. A little history:

I purchased the AutoPilot Dig-220 with the SC-36 cell. Installation and set up was a piece of cake (did it myself).
I previously had a pool service that came once a week to take care of the chemicals and clean the pool. They have since been 'let go' and the Salt system has been running for about 2 weeks now.

I have been bringing pool water samples to a local pool store (every 3-4 days) to see if I need anything. Until today I have added NOTHING except 2 cups of Muriatic acid (as indicated by the results of the water samples). I brought in another sample today and now I need 3 cups Muriatic acid, 3 gallons of liquid chlorine (for a slight build up of algae) and 22 lbs of calcium harness. Here are the readings I got:

total chlorine: 3.0
free chlorine: 3.0
PH: 8.0
Acid demand: 3
alkalinity: 125
Calcium Hardness: 175
Stabilizer: 100
Salt: 2600

AutoPilot says my salt system is at 3500. :shock: I have added NO Salt so I'm assuming this is left over Chlorine.
I set the Power Level to 1 and Purifying Level to 50% (as recommended in the manual). I live in south florida and water evaporation occurs at about 1" every 3-4 days.

I am now seeing a green film in the pool (algae) and why the need for so many products? I can't seem to get a clear idea of how to make this transition as 'clean' as possible. Any suggestions would be helpful. Thanks.


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
Your CYA/stabilizer level is too high! You need to get the CYA level below 100! The only practical way to do that is to replace water.

You need to get your PH down. PH should be kept between 7.2 and 7.8 at all times.

If the AutoPilot unit is happy with the salt level then leave it alone. It is more likely that the pool store number is wrong than that the AutoPilot is wrong.

If you have algae then you are going to need to shock the pool with liquid chlorine (or bleach).

What kind of pool surface do you have? There is no reason to add calcium if you have a vinyl liner.

Once the algae is dead and everything is back to normal, test the FC level in the early evening after a sunny day. If the FC level is high you can lower the percentage. If the FC level is low you can raise the percentage.


TFP Expert
LifeTime Supporter
In The Industry
May 20, 2007
SWSuburban Chicago, IL
Others will chime in but I believe your TA is too high for a SWG which is causing your PH to rise, thus the Muratic Acid.

Your chlorine demand will be higher because your Stabilizer is too high. Consider draining off some of the water ( I know, I know not what you wanted to hear) to get the stabilizer in to a more acceptable level - 60-80 with a SWG.


Well-known member
May 9, 2007
El Paso, Texas
Autopilot manual says TA can be between 80-150 ppm, CYA 60-80 so drain some of your pool water, you can use Jasons Pool Calculator to see how much you have to drain, remember this will also affect your salt, CH levels as well

I know you said you did the install yourself, did you input your pool capacity into the autopilot?, if not maybe this is why your autopilot and test sample is different


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
Rockcrawler said:
did you input your pool capacity into the autopilot?, if not maybe this is why your autopilot and test sample is different
The pool size configuration only affects the number of lbs of salt it suggests you add, not the salt ppm reading. The salt ppm reading will be correct within the precision of the salt sensor (which is normally fairly good)


TFP Expert
Apr 16, 2007
Ft Lauderdale, Florida
Run a TEST POOL PILOT and report the Cell amps and volts.
With the SC-36 cell, your normal voltage range should be 16 - 21 volts. Lower salt levels will increase the voltage level upwards to 29 volts.
At 2200 ppm, I would anticipate your voltage to be about 22 - 26 volts.
If you're around 3500 ppm, the voltage would be about 16 - 18 volts.

Press MENU, the unit will go to TEST POOL PILOT.
Press SELECT, then the diagnostic will scroll on the display automatically.
Jun 9, 2008
Thanks for the replies. I took a guess at how much water to drain before I knew about the calculator so I replaced about 1/4 of the water. I added liquid chlorine for the algae, which looks much better already, and I figured I'd wait for this to settle down and test it again.

The AutoPilot and the pool place both have the same pool size of 15,000 gallons. I checked the voltage and it reads 17 volts and the salt is at 3500 so I'll take that as more accurate than the pool store tests.

I'm hoping the water change will bring my CYA down and my PH down but will it affect the Calcium Hardness? Should I still try to bring that up?