Chlorine Photometer - Automatic machine, anyone used one?

[HarrisonHRG]

Hi All,

I'm looking at putting the following inline on a dosage/sampling feed. - PCA320 Free & Total Chlorine, pH and Temperature Analyser

Has anyone had experience with this device, i'm trying to "fully" automate the chlorine Dosage of my SW pool to achieve correct FC levels at all times.

The standard "set a %" or ORP control isnt working for me, some weeks we will have 0 people in the pool but we could also have up to 200 swimmers in one day, so something like this I hope would adjust to bather load?

Any thoughts? testing twice a day is very time consuming at the moment!

Thanks

 

[reggiehammond]

Any thoughts? testing twice a day is very time consuming at the moment!

Why are you testing twice a day?

As long as FC is safely above minimum per FC/CYA Levels, then why bother with micro-managing FC for bather load and UV changes? Most of us just use a salt water chlorine generator to get away from needing to worry about FC.

Regarding that device - I'm not aware of anything on the market that is able to test FC accurately enough to rely on.

 

[HarrisonHRG]

Why are you testing twice a day?

As long as FC is safely above minimum per FC/CYA Levels, then why bother with micro-managing FC for bather load and UV changes? Most of us just use a salt water chlorine generator to get away from needing to worry about FC.

Regarding that device - I'm not aware of anything on the market that is able to test FC accurately enough to rely on.

The main issue is exactly that, Im hitting FC of over 10ppm if I leave it on say 30%, But the FC will drop to 0.2-0.5 if I lower it and bather load increases?

So the question remains, how do I keep it within parameters when I have to vary the % that the SWG is operating at? It can be so vastly different due to some weeks up to 1000 people can use it for 15 hours per day.

Its just a consistent battle to maintain that chlorine level, but without any bathers it sits perfectly at 3ppm when running 10% "low" mode. As soon as people start using it? I have to increase it, im trying to avoid that process.

 

[ajw22]

Has anyone had experience with this device, i'm trying to "fully" automate the chlorine Dosage of my SW pool to achieve correct FC levels at all times.

It is not possible to fully automate chlorine measurement and dosing.

The thing to understand about ORP is that the voltage detected by the probe is affected by every chemical species in the water. Some of those chemical levels change slowly with time while others can change on an hourly or daily basis. Even certain chloramines can affect ORP levels. So it’s not unsurprising to see diurnal changes in ORP. Have you done an OCLT to determine if something isn’t growing in your water? Overnight loss of chlorine should be less than 1ppm and if it is more than that, then you’re battling two problems at once.

The question to answer is this - what does the ORP signal even mean in swimming pool water?

Sure, the ORP correlates to the FC level, but it is not exact. There have been many studies that have shown ORP probes showing a signal level of >750 mV but the solution only has minimal amounts of FC in it. Then other solutions that show ORP signals less than 700mV with high levels of FC. These variations happen between different probe manufacturers and even within the same line of ORP probes. So, in order for you to specifically know what your system is even doing, you have to map out the correlation of FC to ORP signal over a short period of time (how they vary within a given day) as well as the long term trend. Then you might actually have the ability to know with some certainty what your pool water is doing. While it is generally accepted that an water sample with an ORP signal >700mV is considered “sanitizing” that is only true under very carefully controlled circumstances and, in particular, when a strong oxidizer buffer like CYA is not present.

 

[reggiehammond]

The main issue is exactly that, Im hitting FC of over 10ppm if I leave it on say 30%, But the FC will drop to 0.2-0.5 if I lower it and bather load increases?

So the question remains, how do I keep it within parameters when I have to vary the % that the SWG is operating at? It can be so vastly different due to some weeks up to 1000 people can use it for 15 hours per day.

Its just a consistent battle to maintain that chlorine level, but without any bathers it sits perfectly at 3ppm when running 10% "low" mode. As soon as people start using it? I have to increase it, im trying to avoid that process.

Ah - you're managing a commercial pool, not a residential pool. That's a whole different scenario and not one where TFP methods are really suited.

 

[HarrisonHRG]

It is not possible to fully automate chlorine measurement and dosing.

The thing to understand about ORP is that the voltage detected by the probe is affected by every chemical species in the water. Some of those chemical levels change slowly with time while others can change on an hourly or daily basis. Even certain chloramines can affect ORP levels. So it’s not unsurprising to see diurnal changes in ORP. Have you done an OCLT to determine if something isn’t growing in your water? Overnight loss of chlorine should be less than 1ppm and if it is more than that, then you’re battling two problems at once.

The question to answer is this - what does the ORP signal even mean in swimming pool water?

Sure, the ORP correlates to the FC level, but it is not exact. There have been many studies that have shown ORP probes showing a signal level of >750 mV but the solution only has minimal amounts of FC in it. Then other solutions that show ORP signals less than 700mV with high levels of FC. These variations happen between different probe manufacturers and even within the same line of ORP probes. So, in order for you to specifically know what your system is even doing, you have to map out the correlation of FC to ORP signal over a short period of time (how they vary within a given day) as well as the long term trend. Then you might actually have the ability to know with some certainty what your pool water is doing. While it is generally accepted that an water sample with an ORP signal >700mV is considered “sanitizing” that is only true under very carefully controlled circumstances and, in particular, when a strong oxidizer buffer like CYA is not present.

Yeah, ORP tends to be affected in my experience by Aeration of the water especially, which is what I struggle with when its not in use.

When the pool is not in use, it looses around 0.4ppm of chlorine in 24hrs, I do a non-chlorine SLAM every month min to keep chloramines near 0. I'm pretty sure the water itself is sanitary and clean.

The interesting thing about the chlorine measurement device in the original post is its DPD based, and uses a "flow" photometer, I also dont believe Hanna Instruments make bad stuff....

 

[ajw22]

The interesting thing about the chlorine measurement device in the original post is its DPD based, and uses a "flow" photometer, I also dont believe Hanna Instruments make bad stuff....

Hanna Instruments does not make bad stuff but they are limited by the technology they use. Photometers have their own limitations and quirks, different then ORP measurements or your Palintest chemical testing.

 

[HarrisonHRG]

Ah - you're managing a commercial pool, not a residential pool. That's a whole different scenario and not one where TFP methods are really suited.

A residential pool that is rented, that's correct. But what difference is a commercial pool compared to a busy pool party at someone's house

TFP methods seems to be very well suited, but I'm simply trying to obtain some level of automation based on bather load, which is surely also within the reach of some larger scale residential swimming pools?

Thanks for the reply.

 

[HarrisonHRG]

Hanna Instruments does not make bad stuff but they are limited by the technology they use. Photometers have their own limitations and quirks, different then ORP measurements or your Palintest chemical testing.

Yep,

Im not looking for a "replacement" - Just something which is more accurate at providing a level of FC Measurement, all other parameters dont seem to vary heavily with variation on use.

I'll see if anyone else has some reviews on the equipment before making the plunge into it.

 

[ajw22]

I'm simply trying to obtain some level of automation based on bather load, which is surely also within the reach of some larger scale residential swimming pools?

It is surely not.

 

[reggiehammond]

A residential pool that is rented, that's correct. But what difference is a commercial pool compared to a busy pool party at someone's house

TFP methods seems to be very well suited, but I'm simply trying to obtain some level of automation based on bather load, which is surely also within the reach of some larger scale residential swimming pools?

Thanks for the reply.

Ah - ok. I'm not aware of any practical way to automate this... doesn't seem to exist.
You could run your salt water chlorine generator really hard to keep FC levels quite high, then dose with liquid chlorine based on actual results.

 

[HarrisonHRG]

Ah - ok. I'm not aware of any practical way to automate this... doesn't seem to exist.
You could run your salt water chlorine generator really hard to keep FC levels quite high, then dose with liquid chlorine based on actual results.

The thing is I need to REDUCE my FC levels, not increase them (If i run my salt cell for 24hrs I get literally 15ppm of chlorine)

Trying to keep them low is the challenge here, but not zero, (without checking twice a day obvs lol)

If I have an accurate FC measurement ( from a DPD source ) then I can build a controller to automate the Salt-Cell to literally run it when its needed to meet a setpoint FC level, the Hanna instruments DPD FC measurement device has this as programmable outputs.

Seems that no one has experience of this device, or albeit it isnt necessary for the TFP method. which is understandable... given the cost

 

[Newdude]

A residential pool that is rented, that's correct. But what difference is a commercial pool compared to a busy pool party at someone's house

Its not. But we don't have blowout parties over and over like you would with a commercial pool. (You're engaged in commerce...... so guess what ? )

 

[1poolman1]

Hi All,

I'm looking at putting the following inline on a dosage/sampling feed. - PCA320 Free & Total Chlorine, pH and Temperature Analyser

Has anyone had experience with this device, i'm trying to "fully" automate the chlorine Dosage of my SW pool to achieve correct FC levels at all times.

The standard "set a %" or ORP control isnt working for me, some weeks we will have 0 people in the pool but we could also have up to 200 swimmers in one day, so something like this I hope would adjust to bather load?

Any thoughts? testing twice a day is very time consuming at the moment!

Thanks

The moment you run 200 people through that relatively small pool for that kind of load, you will use up all the chlorine in less than 20 minutes or less. There are no systems I am aware of that can automatically adjust to that kind of load quickly enough.

 

[HarrisonHRG]

The moment you run 200 people through that relatively small pool for that kind of load, you will use up all the chlorine in less than 20 minutes or less. There are no systems I am aware of that can automatically adjust to that kind of load quickly enough.

Putting in a little CYA is a consideration I have to keep a higher FC level, My Salt cell is rated for the pool at 40% and i will use additional chlorine if needed.

200 people over 15 is the ABSOLUTE worse case scenario, I expect 95% of the time to be looking at 30-40 bathers a day.

Hoping the ORP measurement will also reflect that a little and kick in, although I know there is lots of conflicting information on ORP and its effectiveness.

 

[HarrisonHRG]

Its not. But we don't have blowout parties over and over like you would with a commercial pool. (You're engaged in commerce...... so guess what ? )

Thats a good point, and its well made!

Its still early doors, its going to be a long learning curve for me, i've just got to ensure that I keep adequate safe & sanitary bathing conditions for the users, and in the future hoping that'll become more easy with time!

 

[Newdude]

I know there is lots of conflicting information on ORP and its effectiveness

Your problem will be the cell only capable of 0.625 FC per hour in perfect conditions, while the high bather load may deplete many FC per hour. And no two hours will be the same.

There are times the sun will burn off close to what you can produce, for a wash. Swimmers will put you in the negative.

 

[HarrisonHRG]

Your problem will be the cell only capable of 0.625 FC per hour in perfect conditions, while the high bather load may deplete many FC per hour. And no two hours will be the same.

There are times the sun will burn off close to what you can produce, for a wash. Swimmers will put you in the negative.

This is a indoor pool, Glass doors and windows but due to tree-line cover, we are only looking at 1hr a day direct sunlight.

I see lots of contrary information on CYA in indoor pools, Even the salt cell says "DONT LET CYA BE ABOVE 30PPM" , assuming due to its depreciation of ORP values.

Thanks for the information,

 

[reggiehammond]

The thing is I need to REDUCE my FC levels, not increase them (If i run my salt cell for 24hrs I get literally 15ppm of chlorine)

FC/CYA Levels

Curious why you're worried about higher FC levels? That's a good thing, provided you're under SLAM levels.

 

[cwswifty]

...we don't have blowout parties over and over...

... speak for yourself!