Testing Salt Level

[pureluck32]

I was wondering what the best way to test salt level in the pool was. My Circupool system does a salt test and comes back with 3100-3300 range. At the pool stores 1 place uses an electrical meter and it is around 3000 and another store uses the strips and it reads 2100. Any help?

[Pool Clown]

I would take a meter (calibrated) over test strips any day.

[chem geek]

Yes, the test strips can be unreliable sometimes. You can try using the Taylor K-1766 drop-based salt test. If you use the 25 ml sample size, then each drop represents 80 ppm.

[waterbear]

Yes, the test strips can be unreliable sometimes. You can try using the Taylor K-1766 drop-based salt test. If you use the 25 ml sample size, then each drop represents 80 ppm.

ANY testing method can be unreliable if not carried out in the right way. Meters need to be calibrated or they are useless. Strips and regents do expire and need to be fresh. Titration can be done past the endpoint if done too quickly or not mixed properly! I use all three methods and find the strips are probably the easiest for most people to perform properly BUT they must be fresh and kept DRY! I have seen problems with old strips or ones that have gotten moist but I also have seen many problems with meters and with chromate/silver nitrate titration for chloride ions.

Also remember that meters (EITHER handheld or in your SWG) and chemical tests (both drop and strip) are reading different things. Meters are measuring conductivity of the water and are affected by not just the salt present but by the temperature of the water and all the ionic solids besides salt dissolved, which also have an effect on conductivity. They use an internal conversion table to convert the conductivity to a salt reading so they can give a reading that is "off" if the temperature of the water is "out of range" or if the water has a lower or higher level of dissolved ionic solids than the conversion table is based on.

Chemical tests are measuring the amount of chloride ions in the solution so one would think they provide a more 'accurate' picture of the salt level. However, since the rate of electrolysis is really dependent on the conductivity of the water, there are factors besides chloride ion concentration that come into play in the operation of your SWG (such as temperature!)

Bottom line, go by the reading on your SWG since that is the operative reading as far as the proper operation of your system is concerned! If it is within about 800 ppm to a secondary test then call it a day and don't lose any sleep over it! If it is more than that start looking for problems (for example scale buildup on the cell or very cold water if the SWG is reading much lower than a secondary test.)