CYA conversations

[mikemass]

Joy, thanks for the detailed response and that link. Just a few follow ups.. This statement......

Therefore an SWG pool gets a consistently applied dose of chlorine all day long.

is simply not true unless you run your pump 24 hrs a day with the cell set to 100%. See my example above. (Run time 8 hours at 70% = 5.6 hours a day.) Now I don't know if that means the first 5.6 hours of the pump run, the last 5.6 hrs, or somewhere in between. But either way, it is only dosing for 23-1/3% of the entire day and that's during sun-shinning hours.

Also I see what you are saying here:

Your thinking is wrong here. Running at a higher CYA allows your cell to work less, not more.

But these automated systems are not sensing FC and adjusting according. It is the job of the user to set it at 50%, 75%, 100% whatever. So the only thing that allows the cell to work less is me hitting the down arrow on the %'age setting or the pump run time. My statement (albeit maybe simple thinking) holds:

A cell operating 8 hours a day at 90% is working harder than a cell operating 8 hours at 50%.

All this said. In my early years of getting this pool (before I found this forum) I targeted a CYA of 30-50 as recommended by the so called "industry experts" Never once had an algae bloom.

Post discovery of this web site (2012ish) I started shooting for higher CYA levels (60-70) because I was a believer in the real experts here. I was violating the golden rule: "Don't fix what isn't broken". Still have never seen an algae bloom. Basically everything runs quite seamless either way.

This is the first year I jacked it up to that 80 level. (I'm still fixing what isn't broken). We'll see how it goes.

- - - Updated - - -

With automated dosing as the reason for the lower FC/CYA ratio in SWG pools, do pools with automated liquid chlorine dosing (e.g. Stenner pump, ORP based, or liquidator) exhibit the same tolerance for a lower FC/CYA ratio?

Tremendous question. For all intents and purposes, this behaves exactly as a SWG.

- - - Updated - - -

I don't see us changing our recommended level of 70 to 80 CYA when a SWG is in use or the levels of FC for it.

Nor do I. It works. My small sample size (my pool) has proven that over last few years. But us "why" guys like to see it backed up with something more concrete than: "Do it because we at TFP say so and we are always right"

 

[tim5055]

Re: Industry moving toward CYA at or below 50 ppm

But us "why" guys like to see it backed up with something more concrete than: "Do it because we at TFP say so and we are always right"

Unfortunately, sometimes that is all we have. For years the people following these methods were just following what a pool guy said he saw happening in the pools he maintained. It was only much later that folks like Chem Geek started digging and finding multiple studies that had never been tied together before and started painting the picture. The problem is, the picture is not complete yet.

Research follows money. No money, no research. So who has the money? The chemical industry who are selling the things we put in our pools. Do they want to fund research that will probably say stop using a bunch of the chemicals?

I often come back to this - To quote Dave, Site Owner of TFP:

Throughout TFP, you will read that we suggest certain levels that good science and practical experience has taught us fall within safe ranges.

Further reading of posts here will draw you to the inescapable conclusion that these guidelines work.......in thousands and thousands of pools worldwide.

You may or may not choose to use these methods and guidelines or you may use some and not others. Our goal is to teach you what has been proven time and time again and then let you use that information to your benefit.

 

[grottoguy]

Re: Industry moving toward CYA at or below 50 ppm

Mikemass,

You are questioning why TFP is suggesting to use a higher amount of CYA in a SWG. But if I understand correctly, TFP has a standard CYA for a non-SWG pool (which is lower) and is merely suggesting that in a SWG a higher CYA can be utilized to prolong the life of your salt cell. Other than the alleged benefit of prolonging your salt cell, there doesn't seem to be any reason why you couldn't use the CYA proposed for a non-SWG. So if you are not convinced that there really is a cost benefit of having a higher CYA, I don't see why you would raise your CYA to 80. The only other benefit of a higher CYA that I seem to recall is that it may slow the rise of PH (but I'm not sure if I remember that correctly).

My PB set my SWG to run whenever my Pump is on, and I like to run my pump (for reasons other than chlorine production) 12 hours a day, so having a higher CYA doesn't help my cell unless, as you indicated, I dial down the cell percentage. Last year my CYA was generally around 50-60 (so far this year 40) and I always felt that my cell had to work at a high percentage 12 hours a day top produce enough FC. So I am going to raise it to 60 (and maybe 70) now and see if I can dial down my percentage and still produce enough FC. If I can, then a higher CYA will make sense for me.

 

[mikemass]

Re: Industry moving toward CYA at or below 50 ppm

I am going to play with this too over the course of next few weeks. I just had a brand new T-15 delivered yesterday and my salt is at a perfect 3400 ppm. So there should be no variables due to an old cell or improper salt concentration.

 

[chrisexv6]

Ive been CYA-phobic since the days of poolforum.com preaching WHY I should be. Even when I was using tablets, then bleach, then bleach via Liquidator and even now with an SWG, Ive always been of the thought "Id rather use more chlorine than pollute my water with CYA"

Last year I made an effort to go to a higher CYA level than I was comfortable with....cranked it all the way up to 50. While the results were the same as previous years (no algae), the cell runtime necessary to do so was noticeably lessened. So, it obviously helps but isnt required, especially if you are one to keep up with pool maintenance (Im guessing most on TFP are)

I know TFP has the 80 ppm recommendation but Ive never tried that high and dont plan on doing it this season either. But 50 or 60 I could see, which is interesting because that puts SWG in the same range as what is becoming the industry standard recommendation.

 

[mikemass]

Thank you for your first hand CYA experiences. I will try and follow up mine as well.

 

[mikemass]

First follow up. Yesterday (Fri) was first day which I ran the brand new replacment T-15 cell for it's full 8 hour run. (10am-6pm). I had it set to 70%.

Prior to hooking it up Thurs Night:
FC = 4.0 (I was managing with bleach while waiting for cell to arrive)
pH = 7.5
TA = 70-80
CYA = 60-80

Friday ran it for 8 hours (Mostly cloudy day) - Did no tests

Saturday morning (6:30 before sun starting blazing) in an uncirculated pool:
FC = 5.0 on DPD test (so maybe higher)
pH = 7.5

Well this first 24 hours is a good sign. As the FC held and actually increased with the use of the cell. Today I will run the pump same duration, but lower the %'age to 50%. I haven't been able to run as low as 50% in years. Then again this is the highest I have taken my CYA. If 50% is good enough hold these FC levels over the next few days, then I see what you are all saying about making the SWG work "less"

edit: - The reason I give ranges of my TA and CYA reading is because I always question these 2 tests.
For TA the difference between my 7th & 8th drop was barely noticeable. By the 9th drop there was clearly no change at all.
For CYA - I tested 3 times in 3 different lighting conditions. Based on hand calculations, Pool Math, and the amount I added the absolute minimum I can be at is 60. But my dot disappeared anywhere between 80 and 40 depending on the way my eyes perceived it. So I recorded anywhere between 60 - 80.

 

[pooldv]

Then your TA is 80. Here are some reference pics for the CYA test, https://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=36

 

[mikemass]

Follow up 2:

SWG set at 50% and 8 hour run time with a 60 - 80 CYA still holding Chlorine. Saturday had abundant sunshine, but yesterday was another mostly cloudy day. Today will be a better test as it will be full sun all day. I am going to be very happy if I can run this cell at 50% and still have adequate FC levels.

 

[mikemass]

Update #3

Well I am down to 35% and the same 8 hour run time and STILL holding a 5.0 ppm (possibly higher) FC on my DPD test. (FAS/DPD test is in the mail).... This new cell of mine is like a Chlorine producer on steroids! This is tremendous. Because as an extra added bonus with the lower run time on the SWG, not only will I be prolonging it's life, by my pH is no longer spiking. I can't remember last time I added acid and have been holding a pH of 7.5. This pool hasn't behaved like this in 10 years!!!

I set the cell at a measly 15% for today's run.

Side note:
Kid's did swim last night. They were pool for about half an hour. My 13 yr old was complaining of itchy eyes and itchy skin. But my balance has never been better. If my FC is actually significantly higher than 5 pmm, could that cause the symptoms she's describing?

 

[pooldv]

No, not the FC. We swam for a couple of weeks last summer with FC at 28 and CYA at 70 and nobody even noticed. It may not be pool related. But the only thing I would try with your numbers is raising the PH to 7.8 and see if that helps.

 

[mikemass]

Thanks. I take what the kids say with a grain of salt as they are, well you know, kids. Considering my 9 year old had no complaints I am not really that concerned. This Saturday I will be in the pool a good amount myself. I will know if anything feels different. I am running my salt concentration a touch higher than in years past. But nothing that should really matter.

 

[pooldv]

More salt should make that better not worse.