Industry understanding of FC/CYA relationship

[wayner]

Split by moderator from HERE due to hijacking. jblizzle

The minimum FC for 60 CYA is 5 so you're not high at all.

I posted about this in another thread but documentation that comes with a Jandy Aquapure SWCG recommends CYA of 50-75 and FC of 1.0-3.0. It warns you that you should not run your pool above 3.0 FC as that can ruin your equipment.

That is a BIG difference from the TFP recommendations - apparently this is because the Jandy info is very old and doesn't incorporate the proper relationship between FC and CYA. But doesn't this mean that almost anyone using a Jandy SWCG is runnning with FC that is WAY loo low? Is anyone aware of any discussions with the folks at Jandy/Zodiac (or other SWCG manufacturers) about this discrepancy?

 

[jblizzle]

Re: Is my FC too high

All manufacturers seems to parrot the same bogus information that does not take the CYA into account.
My Hayward manual says CAY 60-80ppm (80 best) and FC 1-3ppm ... there is no warning about going over 3ppm that I see though.

If you want a clear pool, follow the FC/CYA Chart.

 

[wayner]

Re: Is my FC too high

I don't disagree with you but someone should be challenging their recommendations. The bulk of pool owners will follow what is in their manual, even if it contradicts what they read elsewhere since that recommendation is specific to their SWCG rather than a generic recommendation. Are there some academic studies that I, as a Jandy customer, can send them to challenge their recomendations?

There is a paper called CYA, Benefactor or Bomb Kent Williams, December 12, 1997, Newcastle, California. But this paper seems to recommend low CYA levels and seems to recommend low CYA levels and suggests that high CYA levels are due to shops trying to sell CYA. And this may predate SWCGs as it doesn't mention them.

So when and how much? When chlorine demands
and costs are out of hand due to hot, sunny outdoor conditions,
when the organic load in the pool is moderate to low, and
when the operator is trained and has time to more closely monitor
water conditions, stabilizing may be in order. Establish levels
of 5 to 12 ppm CYA, or a little more, for your outdoor automated
pool. Allow 20 ppm or so to provide good retention in a
manually treated pool. Don’t EVER use CYA or stabilized chlorine
in an indoor pool, and, even outdoors, please don’t use as
much as the guy who’s selling it suggests...

 

[jblizzle]

Re: Is my FC too high

They will follow what is in their manual until they have a problem, start searching the internet, and find us

Richard {chem geek} has posted many scientific peer-review studies dating back to the 70s that describe the CYA/FC relationship and chemistry to back it up. The specific passage you quote appears to be non-sense, as that author gets some things right, but others wrong. It is also not a peer-reviewed study. Search the forum for Richard's posts (likely in the Deep End or Chemistry 201) and you should find all the information you need ... not that Jandy will likely listen to you, but good luck.

Here start with this thread which references the same paper:
http://www.troublefreepool.com/threads/78565-My-goal-is-to-have-a-CYA-level-of-20ppm-or-less

 

[wayner]

Re: Is my FC too high

Here start with this thread which references the same paper:

Thanks - it seems to me that the SWCG are either incompetent or negligent (or both) in recommending high CYA and low FC. If everyone on this forum knows about this relationship then why don't Jandy, Hayward, etc.

 

[TeamNelson]

Re: Is my FC too high

Great info here & thanks for helping me learn too! My vote is "they Jandy, Hayward" are not as smart as our ChemGeek! He ROCKS!!!+10

 

[jblizzle]

Pool stores continue to give these ridiculous recommendations, likely because that is what the pool chemical companies teach them. Why give good advice if it will cut into profits and sales of magic potions?

I have no idea why equipment manufactures do not provide better info as they are not tied to the chemical companies.
I have to think it is easier for them to say (1-3ppm for FC) than to try to show a table and the FC dependance on the CYA.
You would end up with someone not putting any CYA in the pool and then raising the FC up to 10ppm or something.

 

[wayner]

In this instance it isn't really pool stores since you don't need to buy Cl from a store if you have a SWCG and your target is 2.0 ppm of Cl. Sure you need to buy some CYA but that is more of a one-time purchase.

The SWCG makers seem to get the CYA recommendation about right at 50-75. But how hard is it for them to say that your FC should then be 4.5-6 or something like that?

 

[chem geek]

Virtually all of the SWG manufacturers recommend 1-3 ppm FC and many recommend 60-80 ppm CYA though the latter varies (as in your case). Their recommendations are typically taken from old ANSI/NSPI-5 standards that said 1-3 ppm FC and even later ANSI/APSP-11 standards say 1-4 ppm FC for pools (2-5 ppm for spas) mostly because the EPA has a drinking water limit of 4 ppm FC. Chlorine product regulation is done by the EPA since chlorine is a pesticide so no product label will say that more than 4 ppm FC is allowed for pools (5 ppm for spas). Commercial/public pools are regulated by state (and county or city) regulations and these vary as described in this post where they can exceed the EPA limits, at least in part because they know that higher FC levels are needed when CYA is used, BUT they do not specify ranges in FC/CYA ratio but rather separate ranges for FC and CYA (including no CYA) which doesn't make sense.

The chlorine/CYA relationship has been known definitively since at least 1974 (with the equilibrium constants determined in this paper), but there was no incentive for stabilized chlorine (Trichlor, Dichlor) manufacturers to disclose this relationship and instead they touted the mantra for 40 years that "CYA doesn't matter, only FC matters" so that they could continue to sell their product. They trained their sales reps and distribution channels with this info as well as the pool and spa retail stores. Between the industry, the government, and other organizations, the chemical facts were not disclosed except where required such as in EPA documents (e.g. PDF page 18, document page 12 in this EPA document).

So in part, the EPA is a problem because no manufacturer of a chlorine disinfectant product for pools is legally allowed to recommend more than 4 ppm FC on their label. As for any of these business or organizations understanding the chlorine/CYA relationship, I've talked to some of them and they quite frankly don't care or don't want to know or won't believe the chemistry and instead will just do whatever the EPA, states, or organizations or other manufacturers tell them.

As for the PPOA article that you quoted, we've written about them before on this forum (you can do a search), but just ignore them because though much of what they write is very good, some of it isn't and it will be hard for you to figure out which is which. If you want to see links to many peer-reviewed scientific papers in respected journals justifying the chlorine/CYA relationship and other info, read the thread Certified Pool Operator (CPO) training -- What is not taught. The CPO course is an outstanding course and yet it too doesn't disclose everything that should be disclosed.

So basically we're taking a different tact. We're going directly to residential pool owners via this forum (and The PoolForum that Ben Powell started and runs since he talked about the chlorine/CYA relationship first -- I just helped with the detailed chemistry about it). With over 70,000 registered members and around half a million visitors to the site per month during the peak summer and growing 20+% per year (most years) the fact that the pool/spa industry isn't giving out all the required information will become a moot point.

 

[wayner]

But just so we are clear on this - 100% of people with SWCG that don't frequent TFP are running with an FC level that is WAY too low. Assuming that they target the 2.0 midpoint of the manufacturer's recommendations and the 62 midpoint of CYA then they are running with about half of the FC that they should have.

Doesn't this mean that sooner or later they will all have green and/or cloudy pools, even if the SWCG is always working perfectly?

 

[jblizzle]

That is very possible. They might be ok if they happen to have lower than normal potential for algae.

 

[wayner]

What causes lower than normal potential for algae? Cooler water and air temps?

 

[jblizzle]

Cooler water, fewer algae spores, low algae food levels, etc.

 

[chem geek]

Most commonly it's low phosphate levels. If their fill water doesn't have phosphates in it (some does, used for corrosion control) and if they don't use any phosphonate-based metal sequestrants and don't have blown-in fertilizer, and have low bather-load (cells have phosphates in ATP, ADP, DNA, etc.) then they may be lucky to have a pool poor in algae nutrients. Of course, any use of algaecides (linear quats, Polyquat, copper ions, even 50 ppm borates) will inhibit algae growth to varying degrees.

Cooler pool water helps by slowing down algae growth, but most people heat their pools (some just by using pool covers to retain heat). Nevertheless, at 80 ppm CYA we've most definitely seen SWG pools go south at 2 ppm and some at 3 ppm but almost none at 4 ppm (and I'm talking thousands upon thousands of pools). Remember that the FC target in the Chlorine / CYA Chart for SWG pools is somewhat lower than that for non-SWG pools, partly due to the automated (therefore more consistent) dosing, partly due to the superchorination in the salt cell, partly due to the saltier water. We don't know why for sure but such pools are generally able to go a little lower in FC target than non-SWG pools.

 

[bdex]

My compupool says 40-60cya and 2-3 on FC. So 5%. I have always tried to run 60-70 and 3-4. Had a pool store incident lady year and got my cya up to 150 so been running FC a bit higher buy with use/evap refils it is down to 80 and I keep at 5

 

[bdex]

Most commonly it's low phosphate levels. If their fill water doesn't have phosphates in it (some does, used for corrosion control) and if they don't use any phosphonate-based metal sequestrants and don't have blown-in fertilizer, and have low bather-load (cells have phosphates in ATP, ADP, DNA, etc.) then they may be lucky to have a pool poor in algae nutrients. Of course, any use of algaecides (linear quats, Polyquat, copper ions, even 50 ppm borates) will inhibit algae growth to varying degrees.

Cooler pool water helps by slowing down algae growth, but most people heat their pools (some just by using pool covers to retain heat). Nevertheless, at 80 ppm CYA we've most definitely seen SWG pools go south at 2 ppm and some at 3 ppm but almost none at 4 ppm (and I'm talking thousands upon thousands of pools). Remember that the FC target in the Chlorine / CYA Chart for SWG pools is somewhat lower than that for non-SWG pools, partly due to the automated (therefore more consistent) dosing, partly due to the superchorination in the salt cell, partly due to the saltier water. We don't know why for sure but such pools are generally able to go a little lower in FC target than non-SWG pools.

I would have to guess that some part of 220v running thru metal plates that the water passes over kills algae? But just not enough to eliminate the rascals.

 

[jblizzle]

There is not 220V running through the metal plates in the cell.

 

[svenpup]

Wayner, similar to the 5 stages of grief, new TFP converts must go though their own stages to come to terms with the ignorant or deceptive practices of pool stores, EPA, and pool "professional" organizations.

I think the stages of TFP might be:

• Understanding of the FC/CYA relationship
• Disbelief that all the "professionals" could be so wrong
• Anger that you and other pool owners have been so misled
• Acceptance that the these organizations are unable or unwilling to update their literature, advice and teachings.
• Evangelism to bring others to the teachings of TFP (praise ChemGeek, JasonLion, and Duraleigh)

 

[Smykowski]

Wayner, similar to the 5 stages of grief, new TFP converts must go though their own stages to come to terms with the ignorant or deceptive practices of pool stores, EPA, and pool "professional" organizations.

I think the stages of TFP might be:

• Understanding of the FC/CYA relationship
• Disbelief that all the "professionals" could be so wrong
• Anger that you and other pool owners have been so mislead
• Acceptance that the these organizations are unable or unwilling to update their literature, advice and teachings.
• Evangelism to bring others to the teachings of TFP (praise ChemGeek, JasonLion, and Duraleigh)

This is so stunningly accurate, my jaw just hit the floor. Exceptionally well written, sir.

 

[wayner]

I don't think this is totally fair. I don't think my pool store has been deceptive or ignorant. They have only tried to sell me stuff like bulk liquid chlorine, CYA and pH-. When I posted on here that the pool store said that my CYA was too low I was told that they may be wrong and that I should buy a test kit. So I bought a test kit which confirmed that my CYA was low. I appreciate all of the help that I have received here but I wouldn't say that I have been mislead by anyone other than Jandy/Zodiac and their recommendations regarding FC/CYA. Maybe this is just a Canadian thing but I think there are some decent pool shops out there.