SWG system- why add CYA?

[shoot-straight]

First year pool owner, new concrete pool filled in May. I asked about adding CYA (because of this site) and he said not to bother with it. His logic is that my SWG is only running at 50%, so why add another chemical? I asked about hurting the longevity of the SWG and said its a non issue.

Its been so far so good even in the heat and sun here in MD. FC and TC in "reccomended" range. No algal explosions or other issues.... So- give me a reason(s) to add it at this point.

My variable speed pentair pump runs on speed 3 from 7-9am along with my vaccum, then it goes to speed 1 till 9pm. So its putting chlorine in all day at low levels. Why run my pump all day? Why not? It burns nothing electricwise, and keeping it running while we swim keeps garbage in the skimmers where it belongs.

Im a if its not broke dont fix it kinda guy, but willing to listen.

Regards
Brett

 

[cj3737]

Cya protects chlorine from the sun... sun shines, burns of chlorine that can be used to eat algae... You may not have an algae outbreak yet but, it will surely come..
If you have CYA, your SWG will not work as hard so you can potentially turn it down to maintain proper FC levels..

 

[JesseSchmidt]

Hi and welcome!

How are you testing to know that your FC is staying in the recommended range? CYA acts as sunblock for your chlorine. Without it, your FC level in the hot sun of the day is probably dropping below minimum then coming back up some overnight when the sun isn't hitting it.

Try testing your FC in the morning before the sun hits the pool, then again in the evening around 5-6pm while the sun is still on the pool. That should show you what's happening during the day to your FC level.

Also, what are the recommended levels you are targeting?

 

[borjis]

Well one thing he didn't mention is that without CYA to buffer the chlorine, it will be much more harsh
on clothing & hair.

 

[Donldson]

1. Who is "he"? Your pool builder? If so, then please keep in mind that his expertise is building pools and not pool chemistry despite what he may believe.

2. Your SWG longevity is absolutely an issue, if you can double the life of something that costs several hundred dollars to replace why would you not? Are you saying you run your SWG at 50% 24/7? If so then you are WAY overworking the cell.

3. Our recommended FC levels for an SWG pool about about 1/20th as harsh on swimsuits, skin, hair, equipment and pool finishes as what you are currently running.

So, to summarize, better swimming experience and less stress on all of your equipment especially the SWG cell. I mean, your call, but seems like kind of a no-brainer.

 

[kimkats]

Here is ask also, what recommend range?

We are all about not adding anything you do not need. That is one of the corner stones of TFP.

All of the above posters gave correct answers and whys. It IS up to you. Just keep a close eye on it and let us know your test kit and where you are getting your range from.

 

[pooldv]

More here, ABCs of Pool Water Chemistry

 

[shoot-straight]

Cya protects chlorine from the sun... sun shines, burns of chlorine that can be used to eat algae... You may not have an algae outbreak yet but, it will surely come..
If you have CYA, your SWG will not work as hard so you can potentially turn it down to maintain proper FC levels..

I know what is does, but all good so far. It doesnt get much hotter and sunnier than it is now.

- - - Updated - - -

Hi and welcome!

How are you testing to know that your FC is staying in the recommended range? CYA acts as sunblock for your chlorine. Without it, your FC level in the hot sun of the day is probably dropping below minimum then coming back up some overnight when the sun isn't hitting it.

Try testing your FC in the morning before the sun hits the pool, then again in the evening around 5-6pm while the sun is still on the pool. That should show you what's happening during the day to your FC level.

Also, what are the recommended levels you are targeting?

chlorine in only going in the pool when the pump is running- during the day. its slightly lower in the am, then stays pretty steady all day.

 

[cj3737]

True but if you get a high bather load (kids and yellow streams) that will consume chlorine really fast and your SWG might not be able to keep up. All organics in your pool will eat it up too so unless you are supremely diligent with your tests and adjustments, a little preventative maintenance wouldn't hurt

 

[borjis]

I know what is does, but all good so far. It doesnt get much hotter and sunnier than it is now.

- - - Updated - - -

Again, that won't account for the harsh aspect on clothing & hair with no cya to buffer the chlorine.

 

[JoyfulNoise]

I'd like to see some test results. Specifically, test your water's FC level at the peak of sunlight during the day and then measure the overnight loss of chlorine by measuring FC at sunset and before sunrise. Once you have those numbers, then we can give you advice. This should be done with a proper FAS-DPD test kit, the OTO chlorine test is not adequate.

Here's a tip - pool builders often know next to nothing about water chemistry or water management. They build pools, that's about it. Do you take medical advice from your car mechanic?

Here's what CYA will do for you -

1. Protects chlorine loss from UV;
2 Buffers chlorine and holds it in reserve so it is available for disinfection and moderates its strength;
3. Reduces SWG runtime which protects cell life - SWGs have a finite cell life, about 10,000 hours. The more you run it, the more frequently you have to replace them.

 

[shoot-straight]

1. Who is "he"? Your pool builder? If so, then please keep in mind that his expertise is building pools and not pool chemistry despite what he may believe.

2. Your SWG longevity is absolutely an issue, if you can double the life of something that costs several hundred dollars to replace why would you not? Are you saying you run your SWG at 50% 24/7? If so then you are WAY overworking the cell.

3. Our recommended FC levels for an SWG pool about about 1/20th as harsh on swimsuits, skin, hair, equipment and pool finishes as what you are currently running.

So, to summarize, better swimming experience and less stress on all of your equipment especially the SWG cell. I mean, your call, but seems like kind of a no-brainer.

I did not know about harshness of FC being reduced with CYA. Will read up on that.

I do not have a drop style kit, just two different types of strips. I dont pay attention to the actual numbers, but im always in the "reccomended" range. and- my pool hasnt turned green. YET.

 

[cj3737]

I did not know about harshness of FC being reduced with CYA. Will read up on that.

I do not have a drop style kit, just two different types of strips. I dont pay attention to the actual numbers, but im always in the "reccomended" range. and- my pool hasnt turned green. YET.

We aren't the type of folks to tell you what you "need" We only recommend and give explanations on how and why...
Unless its test kits... you need a test kit to be accurate.. Strips and OTO's just dont contain the info req'd to be accurate

 

[Donldson]

I don't know where all this talk about green pools comes from, CYA does not stop a pool from going green and improper use is more often the cause of green pools. If you are not using CYA then the normal 1-3 FC level is fine for disinfection and algae prevention, though much harsher and more wasteful than any TFP managed pool.

However, since you are using test strips the entire conversion is moot as you don't have any accurate numbers to base your management on. Accurately monitoring your pH, TA, and CH are rather important to keeping an SWG cell working effectively and accurately monitoring your FC is the best way to stay ahead of any problems with pool chemistry or SWG cell problems.

 

[Schadenfreude]

There is also the possibility that you already have CYA in your pool. Whoever opened the pool would normally put some in without the pool builder necessarily being aware of it. Same thing applies if you bought it from a previous owner. In which case, you would probably be keeping your FC levels too low.

Agree on the test kit. I went with the Taylor TF100, which has already saved me several times its cost (get the speedstir - trust me).

 

[GeorgiaPoolOwner]

I'm going to be a dissenting voice here. It is true that if your cya is too low, you will burn chlorine too fast and risk algae. It is also true that if you are combating that with really high chlorine, then high chlorine and low cya can be rough on clothes and hair (as can any chlorine level that is in excess of shock level for the cya level). It is also true that the less you run your SWG and the lower the percentage you run it at, the longer it will last.

However, I am going on the assumption that your CYA is not 0, but around 30-40 (typical for non SWG pools, but low for SWG). Your pool guy told you that it was sufficient. I actually agree that if you keep a CYA around 40 and maintain chlorine at or about 5 ppm without fluctuations throughout the day, your pool should be fine.

I have a SWG, and I keep my CYA at 40, and have had no issues. I do this for a reason.

1) I have an energy efficient pump which I run for 14 hours a day (basically sunup to sundown). The pool has barely affected my power bill. My cell is set to 30%. No matter what time of day I check, the chlorine level is always between 4.5 and 5.5 ppm. Other than opening my pool after being closed over the winter, I've never had a problem with algae and my pool pretty much keeps itself in balance (even then, a SLAM cleared in a couple days). It works for me. The CYA to Chlorine ratio is fine, and is equivalent to what people use in non SWG pools. I could add CYA, and increase the chlorine levels, but if I have a pool that is always in balance every time I test, why mess with what works? As long as the Chlorine/CYA is within the appropriate ranges, and PH and Alkalinity remain balanced, I don't think it matters.

2) The life span of the SWG is a balancing measure. First, my T-Cell 15 sells for less than $500 on Amazon. Amazon.com : Hayward T-CELL-15 TurboCell Salt Chlorination Cell for In-Ground Pools up to 40, 000 Gallons : Swimming Pool Chlorine : Patio, Lawn Garden It's not like I have to pay pool store prices to replace it. Second, 30% isn't a super high rate, even if I am running a bit longer. At this point, I'm happy my pool stays in balance, and the price to pay for a new cell when it eventually dies is not so outrageous that I want to screw with my peace of mind with knowing what is working.

3) It permits me to run the pump at a lower speeds for more hours. I don't like to have my pool not circulating and filtering during the day. Also, filtering works better at lower speeds. With these settings where I have them, the water stays balanced and I can keep the filter running during daylight hours.

Ultimately, I think this place is about understanding your pool, how the chemistry works, what you are putting into your pool, and the importance of proper testing. If you have all of those things, you should be okay. However, the recommendations exist for a reason, so I would not deviate unless you understand what you are doing and why.

 

[robertmee]

^ What he said....I'm pretty much the same way. I have a Sollax SWG and while most TFPers recommend 70 to 80 CYA, I'm more comfortable keeping it at 40 to 50. I keep my variable speed pump running 18 hours a day, just on low speed. We have a single pump that circulates and drives the water features, so it's important that it runs most times that the pool is in use. With the 100 Deg heat we've been having, I'm more comfortable with this balance, than trying to maintain a higher CYA with higher FC load.

 

[BuckeyeChris]

except it's not a higher FC load. Once you get your FC to the target for the CYA level, you are only adding a maintenance dose each day to replenish what was lost during the day. At a higher CYA, this is less FC each day.
The load on your SWG is lower, per day, with a higher CYA. You just need some liquid chlorine to get to the starting point.

 

[robertmee]

except it's not a higher FC load. Once you get your FC to the target for the CYA level, you are only adding a maintenance dose each day to replenish what was lost during the day. At a higher CYA, this is less FC each day.
The load on your SWG is lower, per day, with a higher CYA. You just need some liquid chlorine to get to the starting point.

"Load" was probably an improper term. What I meant was keeping a higher level of FC which is mandatory with a higher CYA. My SWG keeps up fine at a CYA of 50 vs 80, so that allows me to keep a lower LEVEL of FC at 6 vs 9 with a CYA of 80 (I know, non-SWG #). More importantly, on the off chance we need a SLAM, it's much easier to SLAM at levels of 20 than 31. Lastly, with a CYA of 80, the target FC is 9 (yes, I know that's non SWG #...more on that in a minute). That puts it close to the 10 FC limit for testing pH, so that's another consideration. If I'm testing I don't want to have to wait for my FC to drop below 10 just to test pH.

Now I know some of my assumptions are using the NON-SWG FC/CYA relationship, and again that's a choice I've made. FC to CYA relationship is based on the chemical relationship. That relationship doesn't change because you're chlorinating with a SWG. The only reason a lower FC is allowed with a SWG is because presumably the SWG is dosing FC consistently. However, again, it's often recommended that people don't run their pump more than 6 to 8 hours a day, so in trueness, the SWG isn't dosing consistently....It's not much different than adding a gallon of chlorine once in the morning.

Soooooo......long story short, I feel more comfortable with my CYA at 50, and FC at 6, even with the SWG. I've never once had algae (except for a mudslide) and my pool is crystal clear. As long as I'm maintaining a proper CYA vs FC based on chemistry, and not just the fact I'm running a SWG, I don't see any downfall. The SWG is keeping the same target FC of 6 (NON-SWG CYA of 50 vs SWG CYA of 80), and as long as it keeps up with burnoff from the sun at a CYA of 50, I'm good. Yes, I know the SWG may have to produce marginally more FC because with a lower CYA the burnoff is faster, but for me that tradeoff is worth it.

 

[GeorgiaPoolOwner]

"Load" was probably an improper term. What I meant was keeping a higher level of FC which is mandatory with a higher CYA. My SWG keeps up fine at a CYA of 50 vs 80, so that allows me to keep a lower LEVEL of FC at 6 vs 9 with a CYA of 80 (I know, non-SWG #). More importantly, on the off chance we need a SLAM, it's much easier to SLAM at levels of 20 than 31. Lastly, with a CYA of 80, the target FC is 9 (yes, I know that's non SWG #...more on that in a minute). That puts it close to the 10 FC limit for testing pH, so that's another consideration. If I'm testing I don't want to have to wait for my FC to drop below 10 just to test pH.

Now I know some of my assumptions are using the NON-SWG FC/CYA relationship, and again that's a choice I've made. FC to CYA relationship is based on the chemical relationship. That relationship doesn't change because you're chlorinating with a SWG. The only reason a lower FC is allowed with a SWG is because presumably the SWG is dosing FC consistently. However, again, it's often recommended that people don't run their pump more than 6 to 8 hours a day, so in trueness, the SWG isn't dosing consistently....It's not much different than adding a gallon of chlorine once in the morning.

Soooooo......long story short, I feel more comfortable with my CYA at 50, and FC at 6, even with the SWG. I've never once had algae (except for a mudslide) and my pool is crystal clear. As long as I'm maintaining a proper CYA vs FC based on chemistry, and not just the fact I'm running a SWG, I don't see any downfall. The SWG is keeping the same target FC of 6 (NON-SWG CYA of 50 vs SWG CYA of 80), and as long as it keeps up with burnoff from the sun at a CYA of 50, I'm good. Yes, I know the SWG may have to produce marginally more FC because with a lower CYA the burnoff is faster, but for me that tradeoff is worth it.

^This

I'm not recommending anyone just switch to doing it this way. I'm saying it works for those of us who do it, and who run economical VSP's for longer periods of the day with lower cell percentages. I don't want to run my pump for just 6-8 hours, so I don't need a higher CYA or to make more chlorine in a short period of time. The original poster asked if he really needed to raise his CYA when his pool was staying balanced. If your CYA to Chlorine ratio is fine, and the rest of your numbers are in balance, there is nothing wrong with it.