Another salt vs flagstone thread

[LgHorn]

Salt feels better to our skin and eyes because we are salty beings. Our tears have 9000 ppm of salt. A salt pool has 3000-4000 ppm of salt. The ocean has 35,000 ppm. There are lots of folks who add salt to their pool to improve water feel. And, of course, it is convenient because you don't have to haul and add Chlorine to the pool.

Long time reader, 1st time poster here. Thanks to all at TFP for the plethora of info that has helped me many times from pre-construction through the last 9 months as a new pool owner.

pooldv - notice you have a SWG and OK flagstone. Is your stone sealed? If so, with what and how often? If not, have you not experienced any damage or erosion from the salt level necessary for a SWG? There are numerous threads here on the subject, but I chose against a SWG due to the potential risk to my OK flagstone. I've second-guessed that several times to date.

I started with manual dosing of bleach and faced challenges with FC levels until I found my PB failed to add CYA at startup as they were supposed to. I eventually got lazy in the summer and relied on pucks for about the last 6 months, to my detriment. Pool was crystal clear all summer, then about a month ago algae started appearing on the walls and benches of the spa, and a bit on the walls of the pool. Brushing and supplemental LC only helped for a handful of days at a time. Suspecting chlorine "lock" (even though FC level was what I'd been maintaining), and high phosphate levels due to a lot of organic matter dropped from nearby trees and neighboring greenbelt bushes, I tested CYA which had been around 60 at beginning of summer. It was somewhere over 100 according to my test kit. I had water tested at my LPS who read it at 145. I just finished refilling my pool and complete filter cleaning this weekend after a 70-75% drain and thorough brushing. I'm now around 40-50 CYA and FC at 6 having turned the puck feeder to 0 and back to using LC until I decide if I'll go to another method (looking at Stenner pumps). My LPS suggested some "new" CYA-free capsules that go in your skimmers which are chlorine and calcium based. Not sure how this differs from Cal-hypo. Supposedly, my LPS has had good feedback from several of their customers who've used them. Only potential concern reported is the increase in CH that they claim can be managed by regular brushing and backwashing. After my personal experience I'd prefer a pure chlorine method of either sodium hypochlorite or a SWG (except for risk to stone as previously mentioned).

 

[pooldv]

Welcome to TFP!

No, my flagstone is not sealed. It has been installed for five swim seasons and nearly all of it looks exactly the same as it did when it was installed. A few pieces have eroded a little bit. I will always have a saltwater pool.

There are pics and discussion about my flag/salt in my build thread, link in sig. And there is more discussion here, Pictures of Salt Water flagstone or coping damage?

The only way to remove CH from your water is a partial drain and refill with water that has lower CH. There are only a few types of chlorine, more here, Pool School - How to Chlorinate Your Pool

 

[LgHorn]

Thanks for the info.

I guess after reading the discussion you linked to, my primary concern with a SWCG is the flow of saltwater over some of my flagstone for 8-12 hrs/day while my pump runs, as my spa spillway is tiered OK flagstone. There would be some splash out of course from any usage (esp with kids or dogs), but that would be nothing compared to flowing water over many hours every single day. However, I'm sure there are many SWCG pool owners who have natural stone, even flagstone, on their spillovers or scuppers and have not experienced problems. And there's always the option of sealing for some piece of mind (though the reviews on some of these are hit/miss).

Now it's a question of an investment of approx $250 in a Stenner pump, plus the bleach/LC over time, or the higher initial cost of a SWCG. Decisions, decisions...

 

[pooldv]

There have been a few cost analyses of swg vs stenner/bleach and they are pretty close to the same. The real benefit is not having to buy, lug and refill the chlorine on a regular basis. Most folks don't run their spa spillway the whole time they are running their pump/filter. Most people set the overflow as a feature and run it 30 min or so to circulate the spa water. Running that 8 hours a day will push your pH up a LOT.

 

[LgHorn]

Most people set the overflow as a feature and run it 30 min or so to circulate the spa water. Running that 8 hours a day will push your pH up a LOT.

Yeah, good idea...I need to figure out how to do that as the PB didn't set it up that way and I'm not positive I have that capability (think my spa returns/jets are on a manual valve).

Even with my spa spillway running 10 hrs/day I had very stable pH all spring/summer/early fall.

 

[ping]

Yeah, good idea...I need to figure out how to do that as the PB didn't set it up that way and I'm not positive I have that capability (think my spa returns/jets are on a manual valve).

Even with my spa spillway running 10 hrs/day I had very stable pH all spring/summer/early fall.

That was the one benefit of using pucks for chlorine as they are acidic and kept the pH down. But, as you experienced you needed to drain the water after only a season of puck use.

 

[JoyfulNoise]

The basic truth is this - all pools are salt water pools (especially where folks like us live in the arid southwest climates). Chlorine bleach has salt in it and all chlorine reactions (oxidation & sanitizing) turn the chlorine into chloride. Muriatic acid (hydrogen chloride!!) adds chloride ions to your pool. Sweating in your pool adds chloride to it. Your municipal tap water has chloride in it (as much as 200-500ppm)....you get the drift.

So, unless you're exchanging a lot of your pool water with fresh water, it would not be unreasonable for your water to have well over 1000ppm of salt in it to start with and some people find it closer to 2000ppm. So, if salt was going to damage your flagstone spillway, then it's already been present and you should see some effects from it.

I, personally speaking, don't like the use of FS as a spillway material but I understand why people would choose it for aesthetic and design reasons. There are other harder stone materials that would be better suited in a submerged application. So, I would seal FS in a spillway, not for salt penetration reason but for reasons of physical erosion from water penetration damage.