Is FC 4 at end of day with CYA 30 okay?

[Klutz14159]

My routine lately is to test and add liquid chlorine every evening around sunset.

When my CYA was at 20, I noticed that my evening FC was at 3. I added some stabilizer to get to CYA 30 and now my evening FC is at 4.

These FC numbers are at the bottom range of the FC/CYA chart. I'm wondering whether the sun burned through all the available FC during the day and just kind of settles at the low range. At the bottom of the range, am I still getting any chlorination benefits or is bottom range number equivalent of no chlorination?

I'm trying to optimize liquid chlorine usage since liquid chlorine is still expensive compared to a few years ago and I can't go SWCG.

FC 4
CC 0
CYA 30
pH 7.8
CH 250
TA 80

Also, water is crystal clear and I can see right down to the all the cracks in the plaster and the black algae sitting in them.

 

[wireform]

If what you're saying after the sun in the evening you have 4 that would be minimum target and 6 is max target. Keep on what you're doing and just work with the 6 instead of 4. You'll be going through the same amount of chlorine but you'll be on the safer side of a surprise.

 

[Bperry]

My routine lately is to test and add liquid chlorine every evening around sunset.

When my CYA was at 20, I noticed that my evening FC was at 3. I added some stabilizer to get to CYA 30 and now my evening FC is at 4.

These FC numbers are at the bottom range of the FC/CYA chart. I'm wondering whether the sun burned through all the available FC during the day and just kind of settles at the low range. At the bottom of the range, am I still getting any chlorination benefits or is bottom range number equivalent of no chlorination?

I'm trying to optimize liquid chlorine usage since liquid chlorine is still expensive compared to a few years ago and I can't go SWCG.

FC 4
CC 0
CYA 30
pH 7.8
CH 250
TA 80

Also, water is crystal clear and I can see right down to the all the cracks in the plaster and the black algae sitting in them.

If that chlorine test in the evening is before you add more chlorine it’s not too bad. But you’re flirting with danger. You’de be better off and maybe even use a little less chlorine if you increase the CYA to 50-60 and raised the FC to match. The initial raise takes more but maintaining isn’t any different.

 

[mgtfp]

May I ask why a SWG is not an option? Totally understand if it's not within budget right now. Just want to make sure that this decision is not based on misinformation.

Because SWGs are great. Apart from the upfront cost I don't see any reasons against them. Long-term they're much cheaper than liquid chlorine, especially at the current prices. And so much more convenient.

 

[Jimrahbe]

Klutz,

As long as your FC never falls below 4 ppm you are still in the target area and it should work fine..

If this were my pool, I'd increase the CYA to 40 or 50, as that should cut your Liquid Chlorine usage. You have to maintain a higher target value, but you will still use less FC..

I too was curious about why a SWCG was not an option for you..

Thanks,

Jim R.

 

[wolverine]

Get those levels up as the guys are suggesting …Your trending towards a problem right around the corner.

 

[Vandergraff]

I would love to get a SWG - but the reason it looks like it won't work for me tis that our fill water (from a well) has TA of 470.

Pool school says for a SWG.

Adjust your Total Alkalinity to 60-80 ppm. (This is IMPORTANT!)

Adjust your pH to 7.2-7.8 and not any lower. Monitor your pH and when it climbs to 7.8 add acid to lower it back to 7.2 – 7.5 (This is also IMPORTANT!)

It is almost impossible for me to keep TA 60 - 80. I can keep PH in 7.5 - 7.8 range by testing and adding muriatic acid but TA is typically 150 or a bit higher. Trying to get TA lower and keeping it there after refills would mean test and adding acid every day - somewhat defeating one of the main benefits of SWG that you don't have to add liquid chlorine daily and with current cost of acid quite expensive.

 

[Oly]

Also, water is crystal clear and I can see right down to the all the cracks in the plaster and the black algae sitting in them.

Are you testing after you add chlorine in the evening?
What is your daily FCppm loss?
I

 

[mgtfp]

I would love to get a SWG - but the reason it looks like it won't work for me tis that our fill water (from a well) has TA of 470.

Pool school says for a SWG.



It is almost impossible for me to keep TA 60 - 80. I can keep PH in 7.5 - 7.8 range by testing and adding muriatic acid but TA is typically 150 or a bit higher. Trying to get TA lower and keeping it there after refills would mean test and adding acid every day - somewhat defeating one of the main benefits of SWG that you don't have to add liquid chlorine daily and with current cost of acid quite expensive.

That certainly is a challenge. But your CH seems relatively low for a pool with high TA fill water, that often goes together with high CH in the fill water. What is the CH of your fill water?

If you can keep CH low and manage TA, and maybe add Borates, a SWG doesn't seem impossible to operate. Maybe add an automated acid dosing system that you activate after topping up water (@Dirk might want to chime in on that one).

Yes, there is a risk that the cell builds up scale quicker and dies a premature death. But buying a new cell (not the whole thing) every couple of years might still be cheaper than liquid chlorine at these ridiculous prices.

I'm not experienced with operating SWGs in extreme water conditions. Maybe @mknauss has a better experience base?

 

[Bperry]

I would love to get a SWG - but the reason it looks like it won't work for me tis that our fill water (from a well) has TA of 470.

Pool school says for a SWG.



It is almost impossible for me to keep TA 60 - 80. I can keep PH in 7.5 - 7.8 range by testing and adding muriatic acid but TA is typically 150 or a bit higher. Trying to get TA lower and keeping it there after refills would mean test and adding acid every day - somewhat defeating one of the main benefits of SWG that you don't have to add liquid chlorine daily and with current cost of acid quite expensive.

I think the reasoning behind the TA recommendation isn’t that it’ll damage the SWCG is that the industry recommends a higher TA to offset the effects of trichlor tablets. Once you switch away from pucks, the pH will appear to climb faster and a lower TA will help offset that.

 

[Newdude]

Once you switch away from pucks, the pH will appear to climb faster and a lower TA will help offset that.

+1 AFAIK. Interested to see Marty's take on it.




For comparison, we don't reccomend a 470 TA for liquid chlorine pools either, for the PH rise it will cause. You're missing both low 'in' range and high 'in' range for TA by a mile and a half.

 

[mgtfp]

We'll, running a SWG at TA 450 would result in pretty quick scaling of the cell, unless CH was really low. But usually, high TA fill water comes also with high CH.

And depending on CH, TA 150 can still be challenging to keep a cell clean, certainly required good pH control. If Klutz is able to keep CH at 250, it's probably OK. But if it's 250 after a recent drain/refill and expected to rise again, then TA 150 would quickly turn into a problem for cell scaling.

 

[mknauss]

That level of TA is interesting in NCal. Normally means water is coming through carbonate formation, which I don’t believe NCal has.
I would just maintain a pH in the 7’s and TA should stay in the double digits.

 

[Dirk]

If you can keep CH low and manage TA, and maybe add Borates, a SWG doesn't seem impossible to operate. Maybe add an automated acid dosing system that you activate after topping up water (@Dirk might want to chime in on that one).

This is a little out of my scope, because while I have high TA in my fill water, it's not THAT high!

I had high TA when I first filled my pool. I battled it for a while by manipulating pH with aeration. That was bringing TA down, but I eventually gave up. The TA came down on its own after some time, and has stayed put ever since, around 70 or so.

Automating acid dosing is what probably keeps my TA in check (though manual dosing will, too, there's nothing magic about automating acid, it's just easier). But acid won't affect CH, I use a water softener to keep that in check. And a water softener will do nothing for TA! It is the combination of automating chlorine dosing (via SWG) and acid dosing (via a Pentair IntellipH) and filling only with soft water that keeps my pool Trouble Free.

@mknauss took me under his wing when I first came to TFP. Had I listened to him sooner, I would have saved myself a lot of trouble. Start there.

 

[Vandergraff]

Thanks everyone for the responses

That certainly is a challenge. But your CH seems relatively low for a pool with high TA fill water, that often goes together with high CH in the fill water. What is the CH of your fill water?

If you can keep CH low and manage TA, and maybe add Borates, a SWG doesn't seem impossible to operate. Maybe add an automated acid dosing system that you activate after topping up water (@Dirk might want to chime in on that one).

Yes, there is a risk that the cell builds up scale quicker and dies a premature death. But buying a new cell (not the whole thing) every couple of years might still be cheaper than liquid chlorine at these ridiculous prices.

I'm not experienced with operating SWGs in extreme water conditions. Maybe @mknauss has a better experience base?

CH Levels in the pool always been within acceptable range when I tested. I haven't tested the fill water (but will) but I am assuming its not high based on the pool measurements

I think the reasoning behind the TA recommendation isn’t that it’ll damage the SWCG is that the industry recommends a higher TA to offset the effects of trichlor tablets. Once you switch away from pucks, the pH will appear to climb faster and a lower TA will help offset that.

I am using liquid chlorine currently

We'll, running a SWG at TA 450 would result in pretty quick scaling of the cell, unless CH was really low. But usually, high TA fill water comes also with high CH.

And depending on CH, TA 150 can still be challenging to keep a cell clean, certainly required good pH control. If Klutz is able to keep CH at 250, it's probably OK. But if it's 250 after a recent drain/refill and expected to rise again, then TA 150 would quickly turn into a problem for cell scaling.

As above pool CH levels seem fine - last time I tested it was 260. I should add I can't drain and refill - it would put way too much stress on our well to fill the complete pool and getting that amount of water trucked in would be prohibitively expensive.

That level of TA is interesting in NCal. Normally means water is coming through carbonate formation, which I don’t believe NCal has.
I would just maintain a pH in the 7’s and TA should stay in the double digits.

In the coastal mountains which I think are mixture of granite, limestone and the ancient seabed.

Unfortunately maintaining PH doesn't keep the TA in double digits - as above its normally above 150. I have previously tried getting TA below 100 by lowering PH to 7.2 and aerating - but its a week long process and TA goes back up 120+ on next refill....

SWG would be great so I don't have to test and add liquid chorine daily and maybe save some money at these crazy high chlorine prices - however testing and adding liquid chlorine daily and acid as needed has worked great for the last 15+ swimming seasons. Great water quality and clarity (most who use the pool comment on this) and no issues with algae etc. It works but getting expensive buying chlorine and a pain if we are away when I need to find someone else to add chlorine or increase chlorine levels before leaving and use pucks for a week.

That said I sort of do have a salt water pool Last time I looked at adding SWG I tested the pool salt levels which were 1900 ppm - I understand this is likely from my use of liquid chlorine.

 

[Oly]

A Stenner pump and bulk chlorine in a drums would be another solution for vacations and saving a little $ ... maybe. Stenner Pumps Manufacturer of Peristaltic Metering Pumps

 

[Klutz14159]

Are you testing after you add chlorine in the evening?
What is your daily FCppm loss?
I

Only occasionally - I think I lose about 3.5-4ppm per day.

Last few days were interesting because I bought some boxed liquid chlorine on sale at Leslies and my FC dropped each day. After burning through them, I realized they were only labelled 10% chlorine.

Now working through a recent yellow case of deposit bottle chlorine from Leslies and am getting 1-2ppm higher than expected evening readings, but then it burns off during the day.

Haven't done a true OCLT this summer because I'm too much of a night owl to get up at sunrise. But I did do some crazy amounts of black algae scraping past weekend. Got stabbed in hand and foot a few times by very fine stainless steel splinters that fell off the brush towards the end. So probably need a few days to stabilize. Yesterday I measure FC 10.5 in evening, 1pm FC 6, 7pm FC 4.5. Added 112oz chlorine at 7pm and at 10pm got FC 9.5.