100 PPM Salt Loss in 2 Weeks?

[donknotts]

Hello,
First time pool owner here - haven't closed on this house yet but I'm concerned the chlorine cell may be dying. I can't get into the house until 3/14 but I'm concerned.

On 2/15 the Hayward SWG reported 2000 ppm salt. I saw it yesterday and it shows 1900. We haven't gotten much rain in the last two weeks (maybe an inch, tops).

I don't know what kind of pool maintenance is going on. I do know they have the pump set to run 9 hours per day but it's a variable speed pump and I don't know at what speed its running.

I know this is premature but should I be worried about the cell dying? Not sure what else would cause such a drop in salt levels. Not to mention that 2000 as a starting point was already low.

Thoughts?

Thanks everyone!
DK

 

[jblizzle]

That salt level appears to be way too low and a 100ppm difference is within the noise anyway.

You need to independently test the salt level to see if it matches what the SWG is reading. If the SWG is reading much lower than the independent test, then that could mean the cell is dirty or starting to fail.

 

[JasonLion]

Keep in mind that the salt reading on a SWG is essentially meaningless when the water temperature is below 60 degrees.

At 60 degrees and higher, the error in the reading is typically +-400, so some variation within that range is normal.

 

[mas985]

Hayward SWGs usually require a salt level of 2700-4300 ppm. So like Jason said, that is way too low and the cell would not operate at that level so I suspect you are reading the display incorrectly. Which model SWG do you have?

 

[JamesW]

Also, if you can get the first part of the serial number on the box and cell, you can determine the age of each, which can give you some idea of what amount of life might be left (statistically speaking).

 

[donknotts]

Thanks everyone.

My SWG is a Hayward Aqua Rite with the digital readout so I'm pretty confident I'm not reading it incorrectly. It showed 2000 and now it shows 1900.

This is kind of a tough situation because I'm anxious to get in there and get this right but it's not my house for a couple of weeks! It's just sitting empty and I'm not clear if there's even a pool company maintaining it.

Thanks again for your input. I'll try to stay patient until I can get in there and start working on this pool!

DK

 

[ping]

I have a nice digital readout on my SWG and it has about 500 ppm shift in numbers during a months time. I verify my salt content with a Taylor salt test once a month and I haven't added salt for over a year. Pool store testing for the salt level is fine if you don't have your own salt test kit.

When SWG cells start to go bad or need cleaning, a lot of them will start reporting lower salt levels than what the true salt level is. A lot of people make the mistake of adding more salt to the water and going over the amount of salt needed for the SWG to work. You should always have a salt test done before adding any salt to the water, the SWG might be right, but you don't want to have to drain water because you added too much salt.

 

[mas985]

IMHO, the only reason to have an independent salt test of the water is if you want to confirm that the cell is actually failing. This is the only reason I test my salt level. The SWG depends on its own reading of salt level (usually a current measurement) to determine if the salt level is correct or not and really has no idea what you tested so in reality, the secondary test is completely irrelevant to the SWG. The only thing that really matters, is if the SWG measured salt level is within range. Otherwise, the SWG will shut off. So there can easily be a situation where the secondary test is within range but the SWG shuts off because it thinks the salt level is too low. Like when the cell starts to fail. So you are much better off setting pool salt levels by what the SWG reads rather than a secondary test.

Also, it is true that the a dirty cell behaves like a failing cell so one must keep the cell clean to make sure the SWG readout is accurate. But if the cell is failing and you have confirmed that with a secondary test, then you may want to increase the salt level if you want it to work a bit longer before replacement. I plan on doing this when my cell starts to fail. However, you probably don't want to increase the salt level so much that when you do replace the cell, you have to replace some of the water.

Another thing is that I believe the Jandy SWG does not do any temperature compensation for the salt readout where as the Goldline units do. I have a Goldline unit and a spa so I can watch the salt readout as I heat my spa from 50 F to over 100 F and the salt level does not change more than about 100 ppm. It might explain why pings salt level varies so much over a month's time but it also makes it a bit difficult to determine when the cell is failing.