What do you do about the salt?

[cwuffman]

I initially selected the non-SWG method because of the damages to furniture and some types of pool coping that salt was know to cause. After one year of trichlor tablets I ran into all of the problems associated with that method. I then drained most of the water and switched to the BBB (now TFPC) method. A good test kit and a peristaltic pump have made pool maintenance easy and predictable. NO algae or other typical pool problems ever occurred.

One thing that I suppose I hadn't anticipated was how rapidly the salt level would rise using bleach. After the first year of bleach I could taste salt in the water. It didn't seem to be a problem, and no one else could sense it so I just ignored it. After the two years of BBB my family began to notice it. Also, this spring we finally got a reasonable ammount of rain here just north of Houston, and excess water began to flow out of the overflow drain on to the St. Augustine grass in my yard. I noticed that it killed a pretty large patch of grass in an area exactly where the drain was. We have plantings of various greenery between the pool and deck and the previously healthy plants now began to stress and die where the most water splashing occurs. Most of the summer saw less rain and the grass seemed to recover until some recent heavy rainfall and overflow again killed a patch of grass. I have cartridge filters, so water is never flushed and replaced as would be the case with DE or sand filters. I finally just bit the bullet and drained nearly all of the water from the pool and started with new.

Anyway this is in no way a rant or complaint about the TFPC method. I can't think of an alternative that would be better. A SWG would be easiest but I really wanted to avoid salt. I was just wondering if others had experienced this and what they did to deal with it.

If this is in the wrong place or inappropriate, please just move it or remove it.

Thanks,

Carl

 

[chem geek]

For every 10 ppm FC added by chlorinating liquid, bleach, or lithium hypochlorite, it also increases salt by 16.5 ppm. So at 2 ppm FC per day chlorine usage, that is an increase in the sodium chloride salt level of about 100 ppm per month if there is no water dilution.

I use winter rain overflow to keep the salt levels in check and such overflow goes into the sewer drain since that is the local requirement -- pool water cannot go into the storm drain that flows to the bay. The main difference, though, between this salt buildup and CYA or CH buildup is that one can have much higher salt levels before it becomes a problem. For every 10 ppm FC added by Trichlor, it increases Cyanuric Acid (CYA) by 6.1 ppm and salt by 8.2 ppm so with 2 ppm FC per day chlorine usage that's 37 ppm CYA and 49 ppm salt per month. For every 10 ppm FC added by Cal-Hypo, it increases Calcium Hardness (CH) by at least 7 ppm and salt by around 12 ppm so with 2 ppm FC per day chlorine usage that's 42 ppm CH and 72 ppm salt.

So after 6 months with no water dilution, chlorinating liquid, bleach, or lithium hypochlorite would result in 594 ppm salt while Trichlor would result in 220 ppm CYA and 297 ppm salt while Cal-Hypo would result in 252 ppm CH and 432 ppm salt. Obviously, 220 ppm CYA is a pretty big problem. 252 ppm CH may or may not be a problem depending on initial CH levels and the CH in fill water (from evaporation and refill). The 594 ppm salt is not a problem, at least for this one season.

So on balance, the salt buildup is the lesser of evils, so to speak. It is most easily handled by water dilution in order to keep it in check. In my pool, my salt tends to stay in the range of 1000-1500 ppm with winter rain dilution, but I have a lower 1 ppm FC per day chlorine usage due to use of a mostly opaque pool cover.

And yes, as you point out, a saltwater chlorine generator won't build up salt, but it has a higher 3000 ppm salt level in the pool in order to generate chlorine.

Average monthly weather for The Woodlands, TX shows you get rainfall throughout the year -- 49" per year so that's about 4 feet so nearly one pool volume of water for an average 4.5 foot depth pool. Such continual dilution is less efficient where one pool volume equivalent would dilute by about 63%. Also, you probably have evaporation unless you use a pool cover so the rain may just largely be making up for that. This means that you'll need to intentionally dilute your pool water in order to keep the salt level in check.

 

[Griswald]

If you hsve a SWCG, then why add bleach? Thats what the generator is for, making chlorine.

Maybe its me, but I have only added slightly less than 1 gallon so far this season.

 

[chem geek]

The OP does not have an SWCG and is instead using bleach. You are correct that you shouldn't need to add chlorine when using an SWCG unless there are unusual circumstances such as very high chlorine demand where the SWCG may not keep up, especially if it's undersized.

 

[cwuffman]

Thanks for the quick reply, Chem Geek. You must spend an incredible ammount of time hovering over this website. Your input is GREATLY helpful and appreciated. I agree that the bleach method is DEFINITELY the more agreeable method. The last few years have produced significantly less rainfall than is typical of the Houston area. Consequently, most of my water loss has been due to evaporation and the result has been minimal dilution.

I was really just curious about others experiences with the increasing salt issue, it's effects on vegetation and how they deal with it.

Griswald: I am not sure I understand your comment. I don't have a SWCG.

Carl

 

[JamesW]

What is your current salt level?

 

[cwuffman]

I don't know what the salt level is right now as I just drained and refilled with fresh tap water last weekend. Why do you ask?

 

[JamesW]

I missed that you did a drain and refill. Since the topic was salt levels, I thought it would be helpful to know what level was being an issue. Perhaps it would be worthwhile to periodically measure the level to see where it begins to cause effects that you don't want.

 

[cwuffman]

Some time last winter I had salt checked and it was I think around 2700. It would be good to monitor more regularly, which I probably will do. I was surprised when the overflow killed the St. Augustine grass which hadn't happened before even when I was fighting high CYA levels 2 years ago. But it was pretty obvious when each time I had to open the overflow due to rain the grass died or was severly stunted. Then when the other pool plantings in the high splash areas began to die I couldn't find any other variable to blame it on. That is actually the reason for this thread: I was hoping someone else has dealt with this or perhaps could come up with some other contributing factor.

 

[chem geek]

Salt tolerance for plants varies. St. Augustine grass is fairly salt tolerant supposedly up to around 10,000 ppm salt (16 mmohs/cm where 1 mmohs/cm is 640 ppm TDS). Of course, if you have splash-out with evaporation and not regular watering with good drainage then the salt level can build up. That might be what is happening. Before with CYA your salt levels would be roughly half, all else equal. Take a look at this link and see if the description for damage to plants matches what you see. If you aren't using borates, then the damage is likely due to the sodium and chloride.

The other effect would be if the FC level was higher, but usually chlorine isn't a problem and generally reacts with material in the soil rather than with plant material directly.

 

[cwuffman]

Not using borates. Looks like it's what I thought. Thanks Chem Geek. Was going to attach some pictures, but I think it's becoming pointless. TFPC is the best method going.

 

[Tepelus]

Cover your pool when not in use. An opaque cover will reduce the chlorine demand and therefore the buildup of salt will be reduced as well. Drain or backwash when is raining if possible.

 

[Swampwoman]

Just a thought, but in the areas affected by splash out, are you giving them a good soak earlier in the day? If the soil has had a good drink, perhaps the mild saltwater would not impact as greatly...but if pool water is all they're getting...well, plants don't love salt...

 

[cwuffman]

Tepelus: I hadn't thought about the cover. I doubt I do it because it will likely be a couple of years before the salt level will be an issue again and I'll probably just drain it again. Oslo location, pool in south of France! Sounds like a good plan. Where in France if I may ask?

Swampwoman: I may try the "fresh water flush" method when the salt level gets high again.

 

[cwuffman]

Just to show why the concern about this salt issue I have attached a couple of pictures of plantings around the pool. The first is in the splash area and the second is the non-splash area. They had all looked the same before my grandchildren arrived and................ The kids are coming back so the salt had to go.

 

[Tepelus]

Cwuffman: 40km north of Toulon. For me a cover is a must. Not only it helps in the struggle against algae, but it helps keeping the pool clean and the water warm. I use it even though the pool is fitted with a safety dome.