Salt levels and CYA levels dropped a LOT: why?

[skyeboysteve]

Before I switched to SWG, too much CYA was always my nemesis--requiring draining my 20,000 gallon pool every year. I never had to add CYA when I'd refill it, as apparently there was a lot absorbed in the plaster (even new plaster) that would leach back out--plus the tricholor tabs would then continue to raise the CYA from there on out. Cost analysis was that it was slightly cheaper than using bleach and fighting rising pH with Muriatic Acid (even with a huge water bill); plus it was much more convenient and hands off maintenance... but I digress.

Now I'm running a salt water pool where the chlorinator likes to have between 3,000 to 4,000ppm salt.

The pool water looks great currently (better than ever when I was using trichlor), and I've yet needed to ever shock it as combined chlorine is never more than 0.5ppm higher than free chlorine.

Since the days are getting shorter and cooler, I checked my chlorine levels and my free and total chlorine levels indicated 10ppm. So, I cut my power output by half on the chlorinator. It wasn't complaining about low salt at all. However, when I measured my salt levels, they were down to 2800ppm--a drop of 600ppm in just one month!

When I last added salt in April, I had raised it to exactly 4000. In September it had dropped to 3400. So, it had a 600ppm drop in 5 months, then suddenly another drop by the same amount in a month's time.

I had raised my CYA to 60ppm at the beginning of June--never expecting it to ever go down... but measuring it lately, it's less than 30ppm (can't measure less without over-flowing the tube).

I took my water samples to two different Leslie Pool stores, where they gave me readings of 25ppm CYA and 2850ppm Salt...

Is this normal, or what would explain this loss?

Last time I backwashed the pool was in April. I've checked for pool leaks twice (bucket tests) and there doesn't seem to be any (thank goodness because I only just spent $15,000 to fix pool leaks last year).

Thanks for anyone's insight into this.

 

[HermanTX]

There is a couple of things to consider.
Do you have an auto over flow with an auto fill valve? You could be having water exchanges without even being aware.
Also, if you have a lot of rain and it either goes to your overflow system or if you drain then that is another water exchange. All of this could gradually decrease both your salt and CYA levels.
Others may have additional ideas.

 

[skyeboysteve]

There is a couple of things to consider.
Do you have an auto over flow with an auto fill valve? You could be having water exchanges without even being aware.
Also, if you have a lot of rain and it either goes to your overflow system or if you drain then that is another water exchange. All of this could gradually decrease both your salt and CYA levels.
Others may have additional ideas.

I do not have an auto over flow system or auto fill valve (would be nice though). Well, in some ways I think I have a bit of an auto overflow system--called the back of the skimmer box; which has a few cracks at the very top so water can leak out there when the water line gets up to the coping. We have had some rain lately that topped off the pool a couple times, but never imagined it was enough to replace much water. If anything, I'd think the polaris probably spews more water out of the pool than anything; but we haven't been having to add any more water this past month than usual. In fact the water consumption bill was a little lower than the same time last year (I keep logs of each month's water use)... though of course the pool isn't the only water consumer in the house; so not an accurate comparison; especially considering the rain we've gotten a couple times in the past month. Perhaps that's the answer to my issue; but just seems strange that much water could have been displaced. Maybe I need to put a lid on my pool when it rains.

 

[reggiehammond]

Recent heavy rains cause overflow and loss of cya and salt. Totally normal.

Cya also degrades in summer when the pool is warmest. Also totally normal.

 

[JoyfulNoise]

How are you testing for salt?

Losing 500ppm of salt in one month is not at all normal. That would be 80lbs of salt or two bags worth and you would need to exchange more than 2,500 gallons of water to achieve that. That would be a very noticeable water loss of water. Also, rain water tends to “float” on the surface of saline water (because fresh water is less dense than saltwater) and so dilution and overflow from rain really wouldn’t account for it either.

 

[skyeboysteve]

How are you testing for salt?

Losing 500ppm of salt in one month is not at all normal. That would be 80lbs of salt or two bags worth and you would need to exchange more than 2,500 gallons of water to achieve that. That would be a very noticeable water loss of water. Also, rain water tends to “float” on the surface of saline water (because fresh water is less dense than saltwater) and so dilution and overflow from rain really wouldn’t account for it either.

I'm using the reagents that come with the TF-Pro Salt with SmartStir-for pools with SWG test kit. Also both Leslie Pool stores gave me similar numbers for salt this last time. That being said, I only used my own kit when I measured earlier this year.

I agree at the crazy amount of salt loss which is why I'm freaking out a little. I dumped in another 200lbs of salt yesterday to bring it back up to 4000ppm. My wife claims she has not partially drained the pool and refilled it while I was at work either, and she seems to be telling the truth--I think.

That being said, something weird is going on... a month ago we noticed a good swath of grass had died near the plumbing side of the pool. The plumbing for the most part is at least 3 feet below the surface in that area; plus like I said, there doesn't seem to be any leaks. We were thinking perhaps "grub worms" had eaten the grass' roots. It's the first time I've had issues with the grass though even when the pool was leaking--if anything the grass grew thicker and faster in that section than anywhere else in the yard in the 11 years I've had the pool. Perhaps there's still a leak and now that I'm using salt water, it's killing the grass instead of feeding it?

 

[JoyfulNoise]

Are you sure you did the bucket tests correctly by making sure any auto fill was turned off?

 

[skyeboysteve]

Are you sure you did the bucket tests correctly by making sure any auto fill was turned off?

Yes sir... for one thing we don't have autofill. Did the test three times over the summer. Twice with pump running and once without.

Water consumption for property: (which includes watering the lawn)
April: 4K gallons
May: 6K gallons
June: 17K gallons
July: 19K gallons
August: 17K gallons
September: 13K gallons (this number is about average for the last 11 Septembers--though that range has been as low as 5K gallons and as high as 23K gallons.
October: (unknown--don't get waterbill till next week) (assuming the city is all that reliable anyway--I have my doubts).

 

[JoyfulNoise]

That being said, something weird is going on... a month ago we noticed a good swath of grass had died near the plumbing side of the pool. The plumbing for the most part is at least 3 feet below the surface in that area; plus like I said, there doesn't seem to be any leaks.

So this is a big red flag. Grass does not just die in swaths. Especially if it’s coincident with plumbing.

You’re losing water and my guess is the plumbing is leaking. You’re also using enough water each month (10,000+ gallons) that a pipe leak isn’t going to show up in the numbers.

I suggest you call in a leak detecting company to find the pipe. And if the leak is related to the pool renovation you did, then call in that pool company and have them fix it under warranty of it is still in force.

 

[skyeboysteve]

So this is a big red flag. Grass does not just die in swaths. Especially if it’s coincident with plumbing.

You’re losing water and my guess is the plumbing is leaking. You’re also using enough water each month (10,000+ gallons) that a pipe leak isn’t going to show up in the numbers.

I suggest you call in a leak detecting company to find the pipe. And if the leak is related to the pool renovation you did, then call in that pool company and have them fix it under warranty of it is still in force.

I was afraid of that... but that's probably the only logical conclusion. Just when you get done doing multiple tests (including getting 4 different leak detection companies in the past year or so); it's hard to imagine that there would be yet another leak developed; (but bad luck seems to be attracted to me). However, I realize that's not entirely rational--that just because something was fixed that doesn't break down that often (or shouldn't) that you can't get a failure again soon after, especially when one's life seems to be the embodiment of murphy's law. FWIW, the leak detecting companies never found any leaks in the pipes themselves... mostly at the return jets or cracks behind the tiles, and around skimmer.

Wouldn't a bucket test at least show a plumbing leak? Granted, I haven't done one in the past month... so I should probably start there again at least.

If a leak has happened it's been this past month which aligns with the measurements. The waterbill trending down (though as you suggested water use is so high to easily hide a water leak anyway); was probably in part due to all the rain not requiring filling the pool as much or watering the lawn (besides less sunlight to evaporate the water).

 

[JoyfulNoise]

Leaks are difficult things at best to figure out and they are rarely obvious except in the case of irrigation systems where one usually sees a giant wet spot on the ground or a geyser of water from a cracked feeder line. As an aside, I had a plumbing leak in my main water line that was the result of the previous owners low-balling the plumbing work on a casita that they built on the property. Basically they tapped into the main line from the meter to the house with a Tee but because they came up short the plumber decided to try to yank the main line closer to their plumbing run. This resulted in a crack PVC pipe that they then repaired using an irrigation coupler. Totally the WRONG repair job but it allowed them to cover up their work and it held for a few years so no one was the wiser. Fast-forward a few years to me and no matter what I do there never seems to be a consistent water bill. When it should be low, I get high usage. Then the “leak” would disappear and things would seem normal. On top of that I was trying to tease out regular household usage, pool usage, irrigation usage, etc, and there was just no rhyme or reason to any of it. Finally I call in a leak detection company and the guy uses a helium leak detector to pinpoint the location. He strikes gaseous gold (He gas is expensive) and we mark the leak. 3 weeks later the plumber shows up and this is what we find -


The “hidden” coupler patch job!! Well, when pressurized, it would intermittently drip, not drip, and spray water. And of course, because the ground would be saturated there, roots were all over the pipe.

Long story short - you’ll never know what the problem is until you dig into it. Trying to infer when, where and how much of leak you have from external readings will only get you so far. You’ve proven enough in my mind that you have a leak. Now you need to find it. Maybe it is the tiling again, or a wall return … but you’ve definitely got something leaking.

 

[skyeboysteve]

Leaks are difficult things at best to figure out and they are rarely obvious except in the case of irrigation systems where one usually sees a giant wet spot on the ground or a geyser of water from a cracked feeder line. As an aside, I had a plumbing leak in my main water line that was the result of the previous owners low-balling the plumbing work on a casita that they built on the property. Basically they tapped into the main line from the meter to the house with a Tee but because they came up short the plumber decided to try to yank the main line closer to their plumbing run. This resulted in a crack PVC pipe that they then repaired using an irrigation coupler. Totally the WRONG repair job but it allowed them to cover up their work and it held for a few years so no one was the wiser. Fast-forward a few years to me and no matter what I do there never seems to be a consistent water bill. When it should be low, I get high usage. Then the “leak” would disappear and things would seem normal. On top of that I was trying to tease out regular household usage, pool usage, irrigation usage, etc, and there was just no rhyme or reason to any of it. Finally I call in a leak detection company and the guy uses a helium leak detector to pinpoint the location. He strikes gaseous gold (He gas is expensive) and we mark the leak. 3 weeks later the plumber shows up and this is what we find -
View attachment 461352

The “hidden” coupler patch job!! Well, when pressurized, it would intermittently drip, not drip, and spray water. And of course, because the ground would be saturated there, roots were all over the pipe.

Long story short - you’ll never know what the problem is until you dig into it. Trying to infer when, where and how much of leak you have from external readings will only get you so far. You’ve proven enough in my mind that you have a leak. Now you need to find it. Maybe it is the tiling again, or a wall return … but you’ve definitely got something leaking.

What a mess... yes, it's lousy workmanship like that that can cause much anguish and spent money for the next victim...

Wife just did a dye check and discovered that one of the returns we had leaking issues before, is now leaking again. However, it's not on the same side of the pool as the dead grass; but the dead grass probably marks the (general) spot where the actual leak that feeds that return is occurring.

 

[Bperry]

What a mess... yes, it's lousy workmanship like that that can cause much anguish and spent money for the next victim...

Wife just did a dye check and discovered that one of the returns we had leaking issues before, is now leaking again. However, it's not on the same side of the pool as the dead grass; but the dead grass probably marks the (general) spot where the actual leak that feeds that return is occurring.

You might also check for wet areas or algae growth around the equipment. I spotted a very slow leak in my filter that would only show up in the mornings before the sun came out. Once it got warm, the water would evaporate before leaving a puddle.