How long does salt last

[nickadee]

Hi all,

I was under the impression salt in a pool lasted quite a long time. so about 3 months ago I got my pool up to 6000ppm (by adding 200kg of salt, it was at about 5000ppm) and haven't tested salt levels since. I tested just the other day after some heavy rain and I am back down to 3000ppm. It is a big pool, 230 000 L which means i will have to add 700kg to get it back to 6000ppm.

How long does your salt usually last? It is wet season and the pool as overflowed once or twice but i didn't think we would have lost that much water..

thanks in advance.

Nick

 

[Guest]

Salt is lost by spashout, backwashing, overflowing, leaks, etc. What kind of filter do you have? IF you have a sand or backwashable DE filter you will lose some salt at each backwash. Remember that along with salt you will also lose CYA so that will have to be replenshed also.

 

[Strannik]

waterbear beat me to it...

yeah pretty much as he said, salt is only lost when you lose water. Mind you, if you lose water due to evaporation - you don't lose salt as it doesn't evaporate.

Although before putting any more salt in i would give your pool a day to mix the water and then repeat the tests. I have a feeling you didn't lose that much salt, because in order to lose so much salt you had to lose half of your water.

Maybe the water hasn't mixed yet, and you are testing in a spot with more fresh water.

 

[Poolsean]

Make sure also, that your circulation system is drawing from the bottom of the pool too. That is, open your main drain. If you're just sucking from a skimmer and your return jets are pointing towards the top of the water, the heavier salted water will sit in the bottom bowl (deep end) if there's little circulation of the bottom pool water.

I did a start up and I opened the wrong valve. After adding the proper amount of salt to the pool, the Digital was showing 1300 ppm. So did my LaMotte Pocket Tracer. After recalculating the pool volume and initial salt amount, it should have come up 3000 ppm.
It wasn't until I rechecked the valve positions that I realized that I closed the main drain and opened the dedicated suction cleaner line (where there were no cleaners attached). So everything was being drawn from the top surface water, where I took my water sample from too. After opening the correct valve, everything was back to normal within minutes.

 

[nickadee]

It should be fairly well mixed, i have the poseidon (suction pool cleaner) in their every 2nd day or so (our neighbours have a dirt driveway - we get lots of dirt and dust flying into the pool).. i'll open the main drain today and give it a bit of a stir with the broom and measure it again this afternoon. Otherwise I'll have to order a pallet of salt to be delivered in the next few weeks.

I guess I'll need to keep a closer eye on over flow and splash out and top up with salt weekly.

Thanks guys,

Nick

 

[duraleigh]

Nik,

Are you comfortable with the accuracy of your tests?

 

[bluenoise]

It's funny that I just saw this thread as I logged in to post exactly the same situation with my pool.

Last Fall, my pool had a little more than 3100 ppm salt content. The filter has run every day during the winter, but only drawing from the skimmer, not the drain. My SWG says the salt level is 2000 ppm, so I checked with my test strips. They claim 2360 ppm, which is still surprisingly low.

Thinking the issue was as described here with the denser salt water settling into the deep end, I opened the drain valve this morning and turned on the pump. It's been running for over three hours now and the readings are the same. I expected the salt concentration to swing sharply upward since I'm mostly drawing from the drain now, but it's still ~2000 ppm.

I have a cartridge filter and haven't done any backwashing or filter cleaning in about three or four months. I haven't had to top off the water level all winter. We had quite a bit of rain and it reached the overflow point during a couple of the storms, but I can't imagine 30% of my water getting replaced with fresh.

Is there anything else I should be checking for?

 

[Poolsean]

What are you using to test the salt? If you're relying on the SWG's display of salt, the Goldline is affected by colder water temperatures (which will indicate a lower than actual salt level).

Even though you've opened the main drain, the concentration will even out throughout the pool, but again, the SWG's display may not increase properly.

 

[Strannik]

It's funny that I just saw this thread as I logged in to post exactly the same situation with my pool.

Last Fall, my pool had a little more than 3100 ppm salt content. The filter has run every day during the winter, but only drawing from the skimmer, not the drain. My SWG says the salt level is 2000 ppm, so I checked with my test strips. They claim 2360 ppm, which is still surprisingly low.

Thinking the issue was as described here with the denser salt water settling into the deep end, I opened the drain valve this morning and turned on the pump. It's been running for over three hours now and the readings are the same. I expected the salt concentration to swing sharply upward since I'm mostly drawing from the drain now, but it's still ~2000 ppm.

I have a cartridge filter and haven't done any backwashing or filter cleaning in about three or four months. I haven't had to top off the water level all winter. We had quite a bit of rain and it reached the overflow point during a couple of the storms, but I can't imagine 30% of my water getting replaced with fresh.

Is there anything else I should be checking for?

I wouldn't discount the fact that you lost about 25% of your water, if you say it's been a couple of storms. Your pool is not as big as nickadee's so it's quite possible. Although i would give it few days to properly mix the water.

Also another thing to note - your chlorinator's salt reading might be affected by water temperature.

 

[bluenoise]

Thank you, guys, for the replies.

After the pool ran all day, I checked the SWG reading and it still said 2000. I then recalibrated it and it said 2300. To test the salt, I use the Aquacheck strips, which are reading around 2360. That was this morning and I didn't bother testing with a strip again later in the day.

By my estimates, the storms amounted to about 10-14" of increased water in my pool, so it just doesn't make sense to me that that would dilute my salt so much.

I've turned on the solar system, so the pool should start warming up over the next couple of weeks. I'll keep an eye on the salt level and adjust as necessary.

 

[bluenoise]

It's been a few days and the pool has been circulating about six hours a day via the skimmer and the drain. My salt readings are still very low. In fact, it looks like I need to add about 86 pounds of salt to get to my target again.

Currently, my water is around 45-50 degrees F and there is zero chlorine in it. I wasn't too concerned as algae doesn't tend to grow in such cold water (so I thought). Yesterday, I spotted a couple of small patches of green on one of the sunny walls about 20" deep. I just poured in some bleach to bring the FC up to shock level and to help kick off the chlorinating when I get the salt and temperature up to a workable range.

Strange thing about the temperature: When I test the temperature of my water near the surface, it's about 52 degrees. The water coming from the drain, though, is reading 31 degrees for the first few minutes of the pump starting up and then it climbs toward the surface temperature. I find it pretty hard to believe I have such a tremendous temperature difference in eight feet of water and that it could be that cold in my part of the world. I checked the sensor that's reading that temp and it seems accurate for other readings (it's a digital thermometer with a probe inserted into the pipe headed up to the solar panels. There is another that measures the water temp coming back down from the panels).