SWG pool questions (new pool owner)

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Mick967

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Dec 24, 2013
18
Hello folks. New owner, new poster.

Great site!

Just started using my new SWG pool, 60,000 litres. Concrete tiled pool.

I have a few questions that my pool shop people couldn't really help me with so I found this board. I think the first thing any new owner of a pool would tell you is that there is so much conflicting information out there! So, here goes:

1. I noticed a few comments about pool shop testing results being inconsistent. Am I wasting my time going to get my water tested there?

2. The other day it was really hot here (40 degrees Celsius - Australian summer). My kids had just jumped in the pool when I decided to test the water since I read that the sun can consume chlorine. My 4 in 1 Astral Pool testing kit indicated my FC level was around 0.6 to 1.0 (possibly even 1.5 - it's really hard to tell exactly what shade of pink it was). It normally sits at about 3. I took a sample to the pool shop and the result was an FC level of 2.0! What or who do I believe?

3. Why do you recommend CYA levels of 80 or so for SWG pools? Mine read at 35 (according to the pool shop) which, according to them, is fine. Confusion reigns ( in my head).

4. I was told by the pool builder to run the chlorinator for 8 hours per day in summer. I have since found out that some people also run it when the pool is being used. Is this normal practice?

Sorry about the questions. I'm still trying to find my way.
 
Welcome to TFP !!
1. Yes we don't recommend using the pool store for water testing for the reasons you stated. Inconsistent results and not being accurate. The CYA test is usually one they are very bad at.
2. Same answer as the first question. You need to arm yourself with one of our recommended test kits. One of these kits will give you accurate test results you can trust and also us if problems arise. Take a look here pool-school/pool_test_kit_comparison.
3. We recommend a CYA level of 70-80 for SWG to help with FC loss due to the sun. pool-school/water_balance_saltwater_generator
4. Take a look at this for your SWG. pool-school/salt_water_chlorine_generators Yes you can run your SWG while people are swimming.
Spend some time reading in pool school. There is a ton of info there. When you have questions post them and somebody will help you out.
One last thing, if you could add your pool and equipment info in your sig it will help us help you better.
Hope you enjoy the forum!!
 
A little further explanation for you. You're generally gonna hold your FC level at about 4-5 using your SWG. It doesn't take a whole lot of sun/heat/people in pool to lower that number quickly. Since the SWG will produce a little FC at a time, to keep it at a more constant level, you need the higher level of CYA to keep it from burning off so fast. Hope that helps.

Oh yeah, and if for any reason that pool gets away from you and needs to be slammed, we say STILL use plain old bleach to raise to those levels. Forget about "Super-Chlorinate" with the SWG. Common mistake of most newbie SWG owners.
 
Thank you all so much for your replies, and a Merry Christmas to you all.

Can I ask a few more questions leading on from your replies?

Does that mean that the pool shop reading of 2.0 was higher or lower than the actual? They use a test tube into which they put a sample of water and then crush a tablet into it, before placing it into a contraption that the computer reads. I was told by the guys at the shop that the FC reading done "photo chromatically"(I think), was more accurate than the home pool kit.

Does that mean that the kids using my pool were at risk when the FC level was 2.0 (according to the pool shop) when it's supposed to be 4 or 5?

When the pool shop reading came out at 2.0, I didn't throw the kids out of the pool but once they were out, I did not use the pool for 6 days, and ran the pump and chlorinator for 10 hours a day every day ( it was previously being run for 8) on its highest setting and with the pump at maximum speed (5 hours in the morning, 5 at night). The FC reading seems much higher now, although my test kit only goes to 3. Do I still need to SLAM?

I've got about 10 people coming over to use the pool tomorrow afternoon. My pump and chlorinator are due to come on at 8am. The pool will be used from about 3 pm until about 10 pm. Should I run the pump continuously from 8 am tomorrow until the 1pm the next day?

I always thought that turning the pump and chlorinator twice a day for 8 hours made enough chlorine to keep the pool safe whenever we wanted to use it. I'm coming to the conclusion that I'm way off the mark.

Apologies for the questions. I'll get the hang of it eventually!
 
I couldn't tell you if the pool store FC result was right or wrong. I'm not familiar with their method of testing.
I don't think your kids were at risk so to speak, but adequate chlorine levels for your CYA level is important.
Do you have any visible algae ? You would not be able to do the SLAM process with your test kit. You need a test kit that will accurately read chlorine levels of 5 and above. This is why I can't stress enough about getting one of our recommended test kits.
If you never had algae with the way you've been doing things then I think you should be ok for tomorrow. A good sign that your FC levels are dropping off is your water clarity will drop off. If you never had that many people swimming you'll need to compensate for that.
 
I have a question... Why is this site recommending FC Levels of above 3 when any reputable manufacturer recommends between 1-3. High Chlorine levels result in corrosion to the equipment !
Just trying to understand where you are coming from and what this is based on !?

Thanks !
 
Welcome to TFP! :wave:
hhanusch said:
I have a question... Why is this site recommending FC Levels of above 3 when any reputable manufacturer recommends between 1-3. High Chlorine levels result in corrosion to the equipment ! Just trying to understand where you are coming from and what this is based on !?
Click to expand...
The recommended chlorine levels are based on the chlorine - cyanuric acid (CYA) relationship. The higher the CYA level, the more chlorine is needed to provide proper sanitation. This is because CYA acts as a buffer by holding chlorine in reserve, meaning that it lowers the effective strength of the chlorine. The higher the CYA level is, the more intense this effect has on the chlorine. This is why the common suggestion of maintaining 1-3 ppm of chlorine as a "one-size-fits-all" approach is obsolete and ineffective. Here is a chart that shows the recommended chlorine levels at various CYA levels: Chlorine/CYA Chart. This chart is based on the chemistry of chlorine and CYA. This is a foundational tenet of the methodology that we teach and practice.

For a more in-depth technical discussion, see this thread: http://www.troublefreepool.com/pool-water-chemistry-t628.html.
 
hhanusch said:
High Chlorine levels result in corrosion to the equipment !
Click to expand...
Chlorine with no Cyanuric Acid (CYA) in the water is indeed quite strong and more corrosive, but at the FC/CYA levels recommended on this forum, non-SWG pools have the same active chlorine (hypochlorous acid) level as around 0.06 ppm FC with no CYA while SWG pools have the equivalent of around 0.04 ppm FC with no CYA.

The EPA has a drinking water limit of 4 ppm (for pools; 5 ppm for spas) so no manufacturer of chlorine is allowed to recommend an FC any higher than 4 ppm on their labels. However, state regulations for commercial/public pools vary and some exceed this level as described in this post where New York has 5 ppm, Texas has 8 ppm, and Florida has 10 ppm.

The chlorine/CYA relationship is known science since at least 1974. These so-called "reputable" manufacturers generally do not have a clue about chlorine chemistry.
 
Mick967 said:
Thank you all so much for your replies, and a Merry Christmas to you all.

Can I ask a few more questions leading on from your replies?

Does that mean that the pool shop reading of 2.0 was higher or lower than the actual? They use a test tube into which they put a sample of water and then crush a tablet into it, before placing it into a contraption that the computer reads. I was told by the guys at the shop that the FC reading done "photo chromatically"(I think), was more accurate than the home pool kit.

Does that mean that the kids using my pool were at risk when the FC level was 2.0 (according to the pool shop) when it's supposed to be 4 or 5?

When the pool shop reading came out at 2.0, I didn't throw the kids out of the pool but once they were out, I did not use the pool for 6 days, and ran the pump and chlorinator for 10 hours a day every day ( it was previously being run for 8) on its highest setting and with the pump at maximum speed (5 hours in the morning, 5 at night). The FC reading seems much higher now, although my test kit only goes to 3. Do I still need to SLAM?

I've got about 10 people coming over to use the pool tomorrow afternoon. My pump and chlorinator are due to come on at 8am. The pool will be used from about 3 pm until about 10 pm. Should I run the pump continuously from 8 am tomorrow until the 1pm the next day?

I always thought that turning the pump and chlorinator twice a day for 8 hours made enough chlorine to keep the pool safe whenever we wanted to use it. I'm coming to the conclusion that I'm way off the mark.

Apologies for the questions. I'll get the hang of it eventually!
Click to expand...

As Jeff said, we don't (I don't) know how accurate this FC test they have is. I can absolutely assure you that the method we use is extremely accurate, so I would disagree with them on that. I can also tell you that the most accurate FC level will be given as SOON as possible after the sample is pulled. FC in samples degrades rather quickly and once 30 or so minutes passes, you are losing accuracy. Another reason not to rely on the store for this test, though most they run are not always reliable. I've been in the water treatment industry for many years, and waiting more than 15 minutes for testing FC is unacceptable for any level of FC being tested.

As for your pump run times, it's hard to say with certainty since you aren't able to test and have a feel for what run times produce for you in terms of FC residual. Generally, its a good idea have a little extra FC in the pool before and after you have a bather load on the pool. Once you have an accurate way to test this parameter, you'll have a very good feel for what run time lengths do for you.

Welcome to the forum, we are glad to have you here and help you learn. :wave:
 

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Brushpup said:
I can also tell you that the most accurate FC level will be given as SOON as possible after the sample is pulled. FC in samples degrades rather quickly and once 30 or so minutes passes, you are losing accuracy. :
Click to expand...

Thank you both for your replies.

Patrick, does this mean that a pool shop sample will indicate a LOWER FC level than is actually the case since too much time elapses between collection of the sample and the test being performed, causing the sample to degrade? Is that the same for any other measures, such as CYA and pH?

My pool shop results indicate that my CYA is 35, so my FC level should be 2.0 (according to the pool calculator on this site). The pool shop people are telling me that a CYA of 35 is within the acceptable range for a SWG pool, but this site suggests that it should be much higher. Why is that when I am (apparently) producing the right amount of FC for the CYA level in my pool?

I feel like I'm back in chem class.
 
The higher CYA level for SWG is for protection from FC burning off quickly from from the sun, bather load,water temp and the way the SWG produces chlorine. It produces smaller amounts of chlorine over a longer period of time. There for higher CYA level and higher FC levels.
Hope this makes sense.
 
Agreed on the degradation in FC. But you are assuming the pool store test is accurate. We've found that this isn't always the case.

In your particular circumstance, some doubt is cast on it since your own timely testing showed a much lower value. One of the tests is wrong, and it isn't necessarily the pool store's no matter what they are saying. Their test needs calibration, and that isn't always done correctly or often enough.


If your testing is accurate, you will benefit from a higher CYA to protect burn-off of chlorine from UV. Your FC dropped too low to prevent algae growth when there was bather load + sunlight. You could have the SWG run longer and perhaps maintain a high enough FC, but it will be more cost-effective to add CYA.
 
danacc said:
If your testing is accurate, you will benefit from a higher CYA to protect burn-off of chlorine from UV. Your FC dropped too low to prevent algae growth when there was bather load + sunlight. You could have the SWG run longer and perhaps maintain a high enough FC, but it will be more cost-effective to add CYA.
Click to expand...

This may sound a little simple, but if I have a higher CYA, don't I have to run the SWG longer anyway to maintain the higher FC required with a higher CYA? If I'm therefore gong to run the SWG longer anyway, isn't it better to have a lower CYA and not run the risk of not having enough FC for that level?
 
You will run your SWG less with a CYA of 70-80 ppm than you will if you leave your CYA lower. Remember, CYA prevents FC loss from UV. In an outdoor swimming pool, the main cause of FC loss is due to UV from the sun. So, your SWG will have to replace less FC each day with the higher CYA because less will be lost.

You are correct that more and more CYA is not necessarily better and better; it has been shown that a CYA of 70-80 is the sweet spot for SWG pools.

This thread on the subject may interest you: scared-of-cya-magic-target-t68327.html
 
It's the same principle for non SWG pools. The recommended CYA level for those pools is 30-50. A pool with 30 ppm of CYA in full sun all day long is going to lose a lot of FC due to burn off from the sun. Throw in the bather load and it's even more. Bump up the CYA level to 50 ppm and yes you have to maintain a higher FC level also., but you have more protection with 50 ppm of CYA from the sun and bather load so you will lose less FC.
 
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