Faulty salt reading leads to green pool....

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S

sredish

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LifeTime Supporter
Jul 3, 2007
207
North of Dallas
Well, a few weeks ago, noticed the salt reading was down around 2500, so I added a couple bags. 2 days later, it read 2800, so I added a couple more bags, still read 2900. So, I left it for the moment. Where I failed was to not test the salt with a strip before adding. Well, I had to go on a trip and did (forgetting to test the salt level, trusting the reading. Nor did I test the chlorine (I've been getting very complacent an a very well automated setup. Got back from the trip to a green pool.

Tested the salt, it was like 5900 - 6200, don't remember exactly. Salt system was reading 1800 at this time and had kicked off, hence the lack of chlorine and the growth of algae. This was last week. So, I've been fighting the algae with chlorine and it's fairly cleared now, but I still need to keep the levels up for a bit longer. Today, the system is reading 900 ppm of salt, tested it today at 4800; haven't had time to drain water to fix the salt level yet.

Currently the pool is cloudy but clearing. It's also eating chlorine like I've never seen. I've been using simple bleach but due to how quick it's eating it (coupled with 100+ temps) but I've decided to put some tablets in a floater to help keep a steady stream going in as well.

Now for the salt problem. I cleaned the cell about 8 weeks ago right at the start of summer. I was fairly positive I cleaned it thoroughly but, is it possible it's got more deposits on it than I thought, seeing as it's not reading the salt properly? Is there a problem with the cell that I'm not catching? Should I pull the cell and attempt to clean it again or any other suggestions?

I'm running the Hayward T15 cell into a Pro Logic automated system, which kicks off if the salt system if it's not perfect.
 
well, my main question in a unnecessarily long post I guess is, why would my salt generator be reading 900 ppm when my strip is telling me it's near 5000 ppm. I tasted a smidge of the water and it tasted like it was at 5000 ppm for sure.

the algae, I can handle but I want to get my salt reading properly and back online.
 
frustratedpoolmom said:
What's your PH and CYA?
Click to expand...

PH is currently 8.7. Going to pick up some acid tonight, but i didn't figure that would cause the salt to be that far off. I have a bad habit of letting the PH climb some before dealing with it, i just forget to add it then when I do, it's gotten up to 8.5 or so.

and

CYA was 62 last time (6 weeks ago) I checked but haven't since the problem due to the murky unclear water being hard to read accurately.

I'm working on keeping my chlorine around 16 or 17 right now.

edit: I mistyped my CYA at 42 but it's 62.
 
If you have high PH, that can easily cause scale to form on the cell and cause it to not work properly. You need to add acid tonight. If your TA is high, that could be causing the PH to drift up frequently. If your TA is higher than 70, consider lowering the TA to 60-70 so you don't have this high PH problem.

Once you are done shocking the pool with liquid chlorine, and the FC is holding overnight, you ideally should have the CYA level at 70-80 for an SWG.

When the CYA is low, you have to run the swg more to keep up the FC levels. This frequent cell use can cause the aeration that causes the PH drift. By bringing your numbers into the recommended range, you may find your cell operates better.

This all assumes of course there isn't something faulty with the unit that proper water balance won't correct. Read Water Balance for SWGs.
 
Thanks, I tend to keep my CYA at 80 but my pool seems to use water quite a bit and over time I guess from rain and adding water, it's dropped the CYA some and I never raised it back up. I'll get that looked at once the water clears. Haven't tested for TA in a little while, I'll check that out but my PH does drift a lot, more than what it sounds like most people on the boards do with their SWGs, however I do run my overflow pretty regularly to keep the water fresh and sometimes run my waterfall at night to help cool the water (helps with temps but hurts PH you know). And I know I'll end up draining water to lower the salt some so that's not going to help the CYA either.

I unplugged the SWG for a few minutes and replugged it in to try and reset but it came back in at 900 ppm. I'll probably try and clean the whole cell a little better tonight.

Obviously, there's been a problem that's been underlying for awhile and it all came to a head when I left for the week. Now I have the opportunity to face it head on, i just wish it wasn't 100+....
 
I think the reason your are having problems is because there is something wrong with the salinity sensor on the SWG ( for the recored, its not really measuring salt per se but for the sake of this discussion, lets call it a salinity sensor). Since it's reading 900 one day, 1800 another, and close to 6000 by strip/meter, i'm almost certain this is the issue. If the SWG thinks the salt is too lw or too high, it will shut down and not make chlorine. While truw that scale will casue the unit to not operate properly, this is most likely not the problem here. If there is a way to "calibrate" the sensor, you might try that. Ottherwise, i think its worth a call to tthe dealer.

Also, getting the pH back down is a priority.
 
got the acid in the pool along with some bleach to keep the chlorine up. gonna go back out in an hour or so and take some measurements on that. i forgot to keep a little acid on the side to 'reclean' the salt cell so I'll have to do that tomorrow but I want to do that to ensure there's no excess scaling on it before I declare a sensor problem but I have the feeling like there's a little bit of a problem. the cell is 2 years old and has performed pretty flawlessly during that time.
 

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Given the high PH, I would expect calcium scaling, which could throw off the salt reading. You should visually inspect the cell and look for any white crusty deposits. The plates should be either silvery or black and free of debris. If you do see white crusty deposits, the cell should be cleaned according to the manufacturers directions, which usually involves soaking in diluted acid.
 
quite possible
although i wouldn't expect reverse polarity cell to calcify so quickly to the point where it affects salinity readings

but i agree, i'd definitely give it another clean with acid

i'm not sure if you can actually see the plates in T15 cell but ideally you should clean it with acid until it stops foaming
 
Strannik said:
ideally you should clean it with acid until it stops foaming
Click to expand...

that's exactly what I did about 8 weeks ago. Only concern I had is that I wasn't getting it deep enough, but I was pretty sure I did. I let each side soak for a bit until it was no longer foaming, but I think I'm going to try it again before I call the guy who sold it to me to come look at it. He lives right down the street.

First things first, still working the chlorine to get rid of the growth. Pool looks pretty good right now, clearing up nicely, just a slight bit cloudy but can see the bottom which I couldn't yesterday morning. Spa still has some spots in it and I may end up treating it separately. I'll backwash today around lunch sometime to clean out the DE as well, did it last yesterday morning. Should be clear enough sometime today to get a good hard set of numbers, which I'll have as well and get this thing back.

Funny how you take for granted how nice the pool can be with minimal effort. All it takes is one little slip up for you to realize that.... :cheers:
 
Hayward use to NOT have a salt sensor, and I'm not sure if they do yet or not. However, if it does not have a salt sensor, it IS relying on the condition of the cell, water temperature, scale formation, and actual salt level to "guesstimate" what your salinity is.
Remove your cell and acid wash it.

Does the system show you the amps and volts to the cell? This can help determine what's going on also.

Aside from your chemistry being off, I believe you have a scaled cell, or worn out cell. First things first....remove, inspect and clean your cell.

Make sure you keep your pH down.

What is your calcium hardness level?
 
Took the water sample before adding my afternoon delight of chlorine and acid to get to shock level and lower the PH. Have been doing good but work called this morning and I failed to add chlorine this morning, so it dropped some since last nights regimen. As of yesterday have been shocking with cal-hypo and currently have 4 big trichlor pucks in a floaty.

FC 6.2
CC 4.0
PH 8.0
CYA 30
CH 180
TA 194

CYA is low, TA is high, PH is climbing, CH is a little low. lots of work to do.

As said, I've already got more chlorine to get it back to shock level and I've added mur. acid. I have some CYA in the car that i'll start getting in as soon as I get home. should i continue with cal hypo and let the calcium work its way up a little from that?
 
Hayward/Goldline units use the cell conductivity to measure salinity (actually TDS). So one of the symptoms of a failing cell is that the salinity reads lower than it should. However, you should be able to look at the cell plates and tell if they have corroded sufficiently to cause problems (e.g. pits, holes, edges erroded).

Another way to check cell condition is the voltage and amps read out. Voltage should be around +-25v and amps around +- 6a for moderate water temps. Lower than 4 amps but voltage is ok usually indicates a bad cell or a very very dirty cell. A low voltage and amps might indicate a power supply problem but either way if something is wrong with the system, it usuallys shows up as low amps. With that salt level, you should be getting a high salt/amps alarm.
 
Hey mark, thanks a lot. i'll check that out tonight for sure. i have some spare mur acid that i'll maybe attempt to clean the cell again.

a question i have is, adding cya via the sock method, either in front of a jet or a skimmer, is it going to hurt if i turn the pumps off for a little bit... (i.e. for backwashing, etc.)
 
I am having the same problem w/ my aqua rite, salt display reads 2300 then 3100 then 1900 all in the matter of a couple days.
leslies test strip says 5200.
Did you ever figure out why your salt readings were soo much lower than it actually was?
Does anyone know if the sensor is in the cell or the flow switch (if the sensor is bad)?
 

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