Questions about changing to SWCG with regards to generator size and water balance

[Dominique81]

Good day everyone,

Now I use liquid chlorine to treat the water. I have been doing this for two years now according to the TFP method and it works fine.

However, I'm thinking about installing a SWCG and I'm looking into it. Now I have some questions and hope you can help me.

1. You have SWCG that measure Free Chlorine, ORP and Redox (is the same if I’m correct) and where the installation can be set with a percentage.
The IC40 seemed correct and simple for my setup to install, but in Europe it is not easy to get.

Since I have pretty much everything from Astralpool, I looked on their website first and notice a lot of variety.
The installation that measures free chlorine is expensive and someone also said that such a sensor should be seen as a consumable. Furthermore, it only measures up to 5 ppm FC. If your CYA is 80, then you need an FC of 6. So, this option is out.

ORP is not recommended here on the forum. A colleague of mine has such an installation and his problems seemed familiar to me from what I've read on the forum.

Now I found a SWCG on their website where the production can be regulated in steps of 10% (0-90%). So, this is preferable if I understand correctly?


2. My pool is 62 m3 (16K US gal).
The SWCG I have in mind is good for 120 m3 (32k US gal) above 25 Celsius (77 Fahrenheit), 140 m3 (37k US gal) between 16-24 Celsius (61-76 Fahrenheit).

This should suffice or do you recommend its bigger brother 160 m3 (42k US gal) above 25 Celsius (77 Fahrenheit).

I have a single speed pump (2 years old), I am not going to replace it for that reason. The flow is 16 m3/hr (4200 gal/hr), the SWCG for 42K US gal needs 8 m3/hr (2000 gal/hr). So, it shouldn't be a problem in my eyes, except for a slightly higher electricity bill compared to a variable speed pump?


3. The first option makes Cl2: 24 - 30 gr/hr (0.84 - 1.05 ounce/hr) and the second option makes 31-40 gr/hr (1.09 -1.41 ounce/hour).
How many ppm is this? In the summer it can be the case that I use 4 ppm.


4. Water balance
In the instruction book they recommend 5gr/l salt, which equates to 5000 ppm.

On this forum I read the following:
Second adjust CYA to between 70 and 80. The biggest mistake that many SWG owners make is NOT having enough CYA in the water! This can create a lot of problems like high acid demand, algae outbreaks, cloudy water, or early cell failure.
Adjust your Total Alkalinity to 60-80 ppm. (This is IMPORTANT!)
Adjust your pH to 7.2-7.8 and not any lower. Monitor your pH and when it climbs to 7.8 add acid to lower it back to 7.2 – 7.5 (This is also IMPORTANT!)
Adjust Calcium Hardness to 350 ppm for plaster and fiberglass. In any case it should not be much above 400 ppm, or you are going to have to keep close watch on your pH to prevent scale buildup.


My TA prefers to be around 50ppm and sometimes even 40 (I always boost it back to 50). Tried getting it to 80ppm but ended up lowering my pH and thus my TA. At 50 ppm it remains the longest stable.

My pH climbs from 7.5 to 8 in two weeks after I added muriatic acid (about 0.3 Us gal). This is pretty much the whole year through the same.

Will the water in my pool react/behave differently than the last 2 years, by means of salt and higher CYA?

Do you use a muriatic acid dosing pump to keep the pH between 7.2-7.5?

I have the feeling that my consumption of muriatic acid will skyrocket and will also have to add baking soda more frequently if I follow the suggestion to keep it in between 7.2 and 7.5? Or should I keep it in between 7.5-8?

Also, in the same article it says:
Calcium hardness should be brought to 350 ppm. In any case it should not be much above 400 ppm or you are going to have to keep close watch on your pH to prevent scale buildup.

On the TFP website I see also the values below.
ACCEPTABLE MINIMUM: 250-350
IDEAL: 350-550
ACCEPTABLE MAXIMUM: 550-650

Where do you keep your CH at?

Many thanks in advance.

Regards,



Dominique

 

[Texas Splash]

Installing an SWG is a great idea and doesn't need to change a lot about how you manage your pool. Here are some key points:
- Regardless of the type pump, if water is moving enough to keep the SWG on, it is producing chlorine.
- You can use the PoolMath APP (Effects of Adding) and find the SWG you are considering to determine the best output percentage setting and pump run time for your needs.
- As long as the SWG you are choosing is rated for twice the size of your pool, it should work fine.
- No need to force pH low or make major changes to your chemistry. Just follow the TFP recommended levels.
- CYA about 70 - 80, TA just about anywhere between 50 - 90, pH anywhere from 7.2 - 7.8, and CH anywhere from 250 - 550. Lots of flexibility. Again, the PoolMath APP will help you.
- Most common are salt levels around 3,000 ppm +/- 500. It varies by manufacturer. I would start about 3,500 then see how the SWG responds. You can always add more salt, but can't remove it unless you change water.

Hope that helps.

 

[Jimrahbe]

Dom,

1. Do not get a SWCG that measures the FC.. Get the one that just produces chlorine based on run time.

2. You can never go too big with a SWCG, but at a minimum it needs to be rated for 2 x the volume of the pool. Keep in mind that most salt cells shut off when the water temperature is lower than 52 degrees F. In the winter you just revert back to using Liquid Chlorine,

3. If you have a single speed pump, you want to run the cell at say 90% and run it for as short a time as possible that will still generate the chlorine you need. Buying the bigger cell would allow you to run the cell for a shorter period of time. In a 16K pool, 1.4 oz of chlorine gas will increase the FC by .7 ppm.

4. CYA should be between 60 and 80 so that the sun does not consume the FC as fast. Your TA is really the last thing to worry about. In the big picture, TA between 40 and 100 will work fine as long as your pH is stable.

There is no reason to buy an acid pump... I recommend that you run the cell for a year without one and see how thing work on your pool.. Adding a little acid once a week is not a big deal. You can always add an acid pump later if you find you really need one.

Most salt system here use salt levels in the 3500-ppm range.. 5000 seems pretty high to me, but you need to follow the manufacturer's specs.

Thanks,

Jim R.

 

[Dominique81]

Thank you for your reply Texas splash and Jim, very helpful again.

In their manual it says:
Although the salt electrolysis system can work at a salinity range of 3 – 12 g/l, try to maintain the recommended minimum salt level of 5 g/l, by adding 5 kg per m3 of water if the water does not already contain salt. Always use common salt (sodium chloride), without additives like iodides, that is “apt for human consumption”. Never add the salt through the cell. Add it directly to the swimming pool or into the balance tank.

5gr/l is 5000 ppm.


When I use some of the values from two days ago in the app for a swg pool I get the following results:
FC 4 CC 0 pH7.9 TA 50 CH 350 CYA 80 Salt 5000 temp 14 CSI -0,6

In my case I need to boost the CH all the way up to 650, CSI will be -0,33 in winter and -0,09 in summer.
Other option is to choose a system which needs 3000 ppm salt CSI -0,26 winter and -0,01 in summer or as suggested by Texas splash to start at 3000 ppm. In their manual it says it can work, however they recommend 5000 ppm.

However, pH is in all cases 7.9 and I need to keep the pH between 7.6 and 7.9. (depending on temperature), to maintain a reasonable CSI (-0,3 and + 0,3) through the year if I am correct?

Other question I have for both of you, in summertime when you consume about 4ppm of chlorine what is roughly your pump setting and run time? I found this very interesting in the app where it tells you roughly the % and amount of running hours including the information from Jim: In a 16K pool, 1.4 oz of chlorine gas will increase the FC by .7 ppm. This will help me to decide which size of SWG I will get!

Regards,


Dominique

 

[Texas Splash]

I need to keep the pH between 7.6 and 7.9. (depending on temperature), to maintain a reasonable CSI (-0,3 and + 0,3) through the year if I am correct?

Correct. In my case, my pump runs continuously 24/7, so I tend to try and maintain a lower SWG output % rate.

 

[Jimrahbe]

Dom,

I also have a VS pump that runs 24/7..

Jim R.