First pool, first SWG: adding salt at end of season?

[koffie]

This is my first season with a pool, and also my first experience with SWG (EMAUX / Mega SSC25E). I had a little background knowledge on pools, but that's is, so this was a learning season for me.
Right now it looks like the swimming season is over. I will not drain the pool below return jets, but keep the pool up and running and prevent it from freezing over.

Last week I had some troubles with FC, I noticed that after generating 1 or 2 hours (100%) in the moring, the FC was 0 at the end of the day. I increased the running hours and I got at 1.1 last saturday. That day we had a major pool party with a lot of pepole (13 kids, 7 adults) in the pool that day. I genereated 1 or 2 hours in the evening and ran the pump the entire night.
Next day (sunday) I generated about 4 hours. I didn't tested FC, but I noticed my SWG changed from 2 greed LED's to 1 green and 1 red LED. Manual says : "Check salt level/water temperature".
At first I tought the consumption FC was due to microbes or probably algae (water is crystal clear), but the low level warning and the fact that it is the end of the season, we had a lot of rain and debris, and I did a lot backwashing and refill with tapwater makes my believe my salt level is indeed down.

I tested my ppm with a TDS meter, result : 3150 ppm. My SWG manual recommends 4000 ppm.

When I opened the pool, I added 200 kg salt. According to the poolcalculator would my ppm be 4749 at the start of the season. To go from 3150 to 4000 I would need to add 36 kg salt. My salt comes in bags of 25 kg. One bag would raise salt with 594, so 1 bag is not enough. I don;t want to store half a bag so adding 50 kg would raise total ppm to 4338.

My questions : should I consider any change in adding the 50 kg, knowing it is the end of the swimming season?
Is the low FC a result of the low salt level?
Any other considerations?

Total other SWG question : I have set the output on SWG to 100% since day one. I control power to the the SWG with a relay. So the entire SWG computer/trafo is powered down most of the time. Only when I want to genereate, the relay is turned on.
My SWG (as I undestand, like any other) is self cleaning by chaning polarity. How does it now it needs to clean itsel? Is that based on running hours or is meassured by calculating some resistence in the cell?
If it would be based on runinng hours, it is likely that I'm killiing the self cleaning option by cutting power every time, correct?

(extra info about testing : I use Aquacheck Trutest to test FC/pH/FA since that is the only thing I have at the moment. A TF-100 is on the way from USA to NL. My TA is in the 100 rang and pH is around 7.5).

edit: signature says 48000 liters, I used 42000 liters in pool calculator since that is the real value without overflooding the skimmers

 

[ping]

Every now and then you should inspect the SWG for build up even if it is a self cleaning unit. I recommend doing this before adding salt as a build up could cause some of the problems you are having. If it does have build up, then clean it with a 1:10 ratio of muriatic acid to water solution.

If the cell is clean and you want to maintain the chlorine level with the SWG it sounds like you do need to raise the salt level. If you trust your salt reading then overshooting a little is fine. You can always shut down the SWG and maintain the FC with bleach until it gets warm enough next year.

When you get the TF-100 post all the results and we can offer more exact advice as what to do next.

 

[koffie]

The cell is just about 2 months old, so I don't think my cell is dirty? I allways look at all the equipment and heven't seen any visible build up on the cell.
I trust the salt reading, it is a digital TDS meter with 3000 ppm calibration liquid.
Just added 2 bags of 25 kg to the pool, and set the system to circulate the coming hours. I will do a salt test tommorow to see if the ppm is in the range it was calculated.

Anyone has info about the selfcleaning function and the relais I use to cut power?

 

[ping]

Is cell see through? If you can not see inside the cell then you need to remove the cell and inspect it. A + CSI will lead to calcium build up inside the cell on the plates even if the SWG is self cleaning. If the CSI is enough + then the cell can build up enough calcium within a week. You will not see any build up on any other equipment.

Using the relay should be fine and not cause issues with the self cleaning function. You want to make sure there is no way the SWG is on without the pump running though.

 

[koffie]

Is cell see through? If you can not see inside the cell then you need to remove the cell and inspect it. A + CSI will lead to calcium build up inside the cell on the plates even if the SWG is self cleaning. If the CSI is enough + then the cell can build up enough calcium within a week. You will not see any build up on any other equipment.

Using the relay should be fine and not cause issues with the self cleaning function. You want to make sure there is no way the SWG is on without the pump running though.

The cell is in clear housing, but I understand I have to remove the cell to take a good look. Will do that this week - didn;t see any build up when looking in normal operation.
I have an extra rule on the poolcomputer that forbids the relais to be on when the pump is not. You simply cannot turn the SWG on when pump is off - and when pump is powered off for whatever reason the SWG is also shutdown.

In understant that the self cleaning (by changing polarity) is done based on some measurments from the cell?

 

[ping]

It is based on the on time and it will switch the polarity every so often. The SWG should retain the run time when power is not supplied to the unit.

Hopefully adding the salt will get the SWG performing again.