Chlorine Level and Overall Use

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JPMorgan

JPMorgan

Gold Supporter
May 22, 2018
847
Elmhurst, IL
Pool Size
60000
Surface
Plaster
Chlorine
Liquid Chlorine
If I keep the chlorine level at the higher end of the range for the corresponding CYA level, will I use more chlorine over the course of the summer? For example, at CYA level of 40, the recommended chlorine level is 3-7 ppm. If I maintain the FC at 6-7 rather than 3-4 will I end up using significantly more chlorine? Or will I use approximately the same amount (except for the initial higher dose)?
 
All else equal, the sun will burn off slightly more chlorine at a higher FC level, yes. It's also fair to say the difference may not be large enough for you to detect.

I say all else equal because one of the pools I look after has a waterfall at one end that allows some surface runoff during really bad rainstorms. When that occurs, I'm glad to have a slightly higher FC level in the pool, because I avoid a SLAM, and end up using less total chlorine. A similar situation would be occasional large swim parties of lots of kids. Bather load can exhaust the chlorine very quickly, and depending how often it's being tested, FC could get too low.

Your pool is quite large, and therefore the quantity of free chlorine is also large and short term impacts will be less noticeable. In a smaller pool, a dozen bathers can have an impact remarkably quickly.
 
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You CAN NOT ....:"Maintain" your FC level at 3 or 4. That is the minimum and edge of danger zone. 6-7 is your target and allows for losing down to that bare minimum.

What is your daily FC loss? You may need to raise that cya level if it's over 3 at 40.
 
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woodyp said:
You CAN NOT ....:"Maintain" your FC level at 3 or 4. That is the minimum and edge of danger zone. 6-7 is your target and allows for losing down to that bare minimum.

What is your daily FC loss? You may need to raise that cya level if it's over 3 at 40.
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In Illinois, the regs say that a pool must be shut down if the FC exceeds 5 ppm. Given this (uninformed) rule, what CYA/FC levels would you shoot for... 40 and 5.... 30 and 5?
 
JPMorgan said:
In Illinois, the regs say that a pool must be shut down if the FC exceeds 5 ppm. Given this (uninformed) rule, what CYA/FC levels would you shoot for... 40 and 5.... 30 and
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JPMorgan said:
Yes…. this is a pool in a condominium complex.
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If it were me, I'd stick to 10% FC/CYA, therefore 50 ppm CYA and topping up to 5 ppm FC with a minimum of 3 ppm FC before topping FC back up. I'd want to have a dosing system such as a salt water chlorine generator or liquid chlorine feeder, and perhaps a weekly or bi-weekly OCLT to be certain that algae is not causing extra FC consumption. Nascent algae would consume more chlorine than you'd lose due to a sub-optimal CYA level. Your 40 ppm CYA level is fine and would give you more room for error when hemmed in by your stipulated maximum.

Note that troublefreepool is geared primarily toward residential pools. This is because of various and plentiful failures of the mainstream pool industry and pool regulators to base recommendations on science and facts.
 
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JPMorgan said:
Yes… 100 (which seems way to high). Once at that level at least 50% of the water must be drained.
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It seems that the regulations require you to operate the pool in a manner which will cause you to use a lot of chlorine by keeping the CYA low and allow you to maintain a chlorine level high enough to keep the pool clear. I wish you a lot of luck, they have you walking a very tight rope. Keeping the chlorine below 5ppm (according to TFP standards) requires you to have a CYA of 40 or lower. To maintain these standards may require either constant sodium hypo additions or multiple additions of sodium hypo per day along with multiple tastings per day to verify you are not violating the regulations and still maintaining the pools levels, again, I feel for you, it doesn't sound like an easy job.

2023-06-27_9-44-56.jpg
 
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needsajet said:
If it were me, I'd stick to 10% FC/CYA, therefore 50 ppm CYA and topping up to 5 ppm FC with a minimum of 3 ppm FC before topping FC back up. I'd want to have a dosing system such as a salt water chlorine generator or liquid chlorine feeder, and perhaps a weekly or bi-weekly OCLT to be certain that algae is not causing extra FC consumption. Nascent algae would consume more chlorine than you'd lose due to a sub-optimal CYA level. Your 40 ppm CYA level is fine and would give you more room for error when hemmed in by your stipulated maximum.

Note that troublefreepool is geared primarily toward residential pools. This is because of various and plentiful failures of the mainstream pool industry and pool regulators to base recommendations on science and facts.
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I am working with the HOA on installing a liquid chlorine feeder. I think that will make a huge difference, as I will be able to maintain FC at 5 ppm consistently with the existing Aquasol Controller. Right now the pool has a trichlor feeder which I keep turned down (to limit CYA build up) and then primarily dose the pool with liquid chlorine. Based on the feedback I'm getting here, I'm going to shoot for 40 CYA and 5 ppm FC and see how that goes. If we don't have the liquid chlorine feeder by next season, I may just step out of the role... too much responsibility without the right equipment. The good part is that people here have really noticed the difference with someone managing the pool by TFP protocols. I get compliments all the time. One guy recently said the pool was "not swimmable" until I got here and started managing the pool.
 
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JPMorgan said:
I am working with the HOA on installing a liquid chlorine feeder. I think that will make a huge difference, as I will be able to maintain FC at 5 ppm consistently with the existing Aquasol Controller. Right now the pool has a trichlor feeder which I keep turned down (to limit CYA build up) and then primarily dose the pool with liquid chlorine. Based on the feedback I'm getting here, I'm going to shoot for 40 CYA and 5 ppm FC and see how that goes. If we don't have the liquid chlorine feeder by next season, I may just step out of the role... too much responsibility without the right equipment. The good part is that people here have really noticed the difference with someone managing the pool by TFP protocols. I get compliments all the time. One guy recently said the pool was "not swimmable" until I got here and started managing the pool.
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Sounds like a solid plan.

A lot of municipalities, whether local or state, are using very antiquated levels that don't account for more recent (like, the last 2-3 decades) of pool science to show the FC/CYA relationship. It certainly makes it a challenge to keep a sanitary pool!
 
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Great work making the pools better and showing the residents what sparklypoolitis can achieve.

One advantage you have is 38" average annual rainfall - somewhat similar to what we have here in Sydney. That's a helper in terms of dilution of CYA arriving from trichlor over time. My situation is simpler than yours, but I make use of trichlor as well.

You could propose salt water to the owners, which is nice to swim in, and enables a salt water chlorine generator. Results in less lugging of chlorine to get the job done.

Something else to consider is a second puck feeder, well marked, and used for calcium hypochlorite (cal hypo). For safety reasons, you need to prevent any possibility of dropping a cal hypo puck into a feeder used for trichlor. Cal hypo would contribute to your calcium, which you may have been adding (I don't know your fill water analysis, maybe heaps coming in that way so cal hypo would be unhelpful). A problem with those is that cal hypo pucks dissolve much faster than trichlor. A safer (and no equipment) alternative is adding the powder as part of your chlorine program. At least it's less lugging of stuff than chlorinating liquid.
 
needsajet said:
You could propose salt water to the owners, which is nice to swim in, and enables a salt water chlorine generator. Results in less lugging of chlorine to get the job done.
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Thought about this, but it's my understanding we would need to add a lot of salt to a 60,000 gallon pool and then monitor salt in the pool. I think I'm more comfortable with liquid chlorine.... seems a little simpler to me and something I am already very familiar with. I could be persuaded, though!

With a 50 gallon tank, it would only require filling the tank about every three weeks, so that's not too bad. Could start purchasing 5 gallon containers of LC to make the fill job a little easier.
 
Started carefully monitoring FC use today with CYA at 40. Turned down the Trichlor feeder so there is no FC being added that way. Raised FC to 5 this morning. At about 5 pm I had to add about 2 ppm of FC (1 gallon of 12.5% LC). Will test again tonight and again tomorrow morning. Overcast today, so the pool is not getting much sun or use. Will see how much LC I need to add in the next 12-15 hours. For our 60,000 gallon pool, every half gallon is about 1 ppm FC, so it makes the calculations very simple. Hoping that 2 gallons per day will maintain pool between 4-5 ppm.
 
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Sure enough, salt replenishment is an important consideration. You likely have 500 to 1000 ppm already, which helps some. I test salt a bit seldom myself, mostly just watch the indicator on the controllers, plus I have a salt pen ($15) and a drop test as backup/verification of my methods. It would be worthwhile (if this ever becomes an option) to choose a SWCG with low (3000ppm) salt spec, which I think is also helpful. One that I look after is 5000-6000 ppm and that's a little more painful.

But yes, liquid would be great. I've heard of injectors set up at around $400-$500 by the DIY types. Also, some suppliers offer chlorine delivery.

Glad to hear about the monitoring. I'd definitely be doing Overnight Chlorine Loss Test on both pools periodically.
 
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JPMorgan said:
Thought about this, but it's my understanding we would need to add a lot of salt to a 60,000 gallon pool and then monitor salt in the pool
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You would need about 40, $8 bags to start from 0. It's entirely possible to start already halfway there.

Unless we get crazy rain, I top mine off mid season with 1 or 2 bags. With double the pool, you'd need 2 to 4. $36 tops.

I test the salt monthly. It's as stable as the CYA and CH.
 
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