Will salt concentrations change output potential of a SWG

[TreeFiter]

Lately we've been seeing a number of our pools with SWGs with low salt, but everything shows they are working fine. Most of the pools in question are using EcoMatic SWGs. The Ecomatics read 100 when salt levels are where they should be, or at least thats how they are supposed to work. When salt levels drop below about 2500ppm, the number will drop below 100. There isn't an exact conversion for what the numbers mean as far as I know, but usually you can tell when it says 96 it only needs a little bit of salt, and if it reads 75 it needs more.

The pools I've been seeing will read 100 as if salt levels are fine. When I test the salt, I get all kinds of readings, which are all below the operating range. I've seen some as low as 1500ppm, yet the display still says everything is fine. I also see that the system is generating, based on the cloudiness at the cell. So up until now I have been assuming that if the pool is generating, it should be fine. I'm wondering if that is correct, or if a pool generating with a salt concentration of 3000ppm is working more efficiently, or generating more chlorine than a pool with a salt concentration of 1500ppm.

These systems are supposed to shut themselves down when salt levels are too low to operate. Will running with low salt damage the cell? Why might this be happening? Why aren't the systems picking up on the low salt level? Any thoughts?

 

[JasonLion]

Re: Will salt concentrations change output potential of a SW

Most SWG systems automatically adjust their voltage to compensate for the current salt level, however a few brands use a fixed voltage, which results in producing more chlorine at higher salt levels and less chlorine at lower salt levels. From what I can see the EcoMatic units do not compensate for the salt level, so their output varies (but I'm not certain of that).

 

[TreeFiter]

Re: Will salt concentrations change output potential of a SW

Do you have any thoughts as to why they are saying everything is OK even when the salt levels are very low?

I'm thinking that a lot of the issues we are seeing with no chlorine in pools might be triggered by low salt that goes undetected because according to the SWG display, everything is fine. By the time we realize the salt is low, algae is already starting to grow, and the SWG can't keep up with it.

 

[chem geek]

Re: Will salt concentrations change output potential of a SW

That sounds plausible. If they don't adjust the voltage when the salt level drops, then the output will drop and it is a non-linear relationship because at lower salt levels more oxygen gas is produced instead of chlorine. Basically, at some cutoff, hardly any chlorine is produced. So you are right that if the display says everything is OK but the actual salt level is too low, then there won't be enough output to maintain the chlorine level at the same on-time percentage and may even be low enough output that 100% on-time is not enough.