Can Iron effect SWG efficency?

[Sidecarist]

Can iron in the water cause the SWG to be less efficient? My SWG can't keep up with loss from the sun let alone swimmer load. Current numbers are: FC 5 CC 0 PH 7.6 TA 70 CH 270 CYA 75-80 SALT 4000 If I run 24hr a day at 100% it will maintain FC of 5 to 6. I am currently trying 12hr run time to see what I get. With my low swimmer load FC of 3 to 4 may be enough to get me through the next month or so until closing. The pool is at our current summer home, soon to be permanent home so I'm not here enough to supplement with bleach or I would. It's also very rural so I don't have anyone that I can trust to keep an eye on it when we're away. Currently I have Iron stains that I am treating with HASA Super stain out. It is working and has reduced the staining in just a couple of days significantly. I will do a full Ascorbic acid treatment in the spring too. then will look into ways to remove the Iron from the water (CuLator?). The real question is the Iron causing my SWG to be less efficient, or is my SWG just getting old and less efficient on its own. I cleaned it per the mfr instructions, and clearly working to some degree but just not keeping up. If Iron is a problem for SWG what is the solution? Or am I just shopping for a replacement SWG over the off season? Thanks to all in advance everyone has been helpful in getting me through my first and then 2nd SLAM your advice has been spot on! Bob

 

[JamesW]

The iron should not be affecting the performance. Was the cell scaled? I think that the IC20 has half of the plates as an IC40. So, it's not a big producer but your pool isn't very big so it should keep up.

How old is the cell?

 

[Sidecarist]

It's not scaled. The plates look spotless and clean. As a precaution I did clean it per the mfr instructions with no improvement.

I don't know the age of the cell. The pool is 8 yrs old but I don't know the age of any of the pad equipment.

I had to go away for the weekend. So I put a puck in a floater for now. On Sunday I'll set the FC to 6 and start testing 3 times a day and post the results. The water is very clean and for the last 3 days the CC has been 0.5 or 0, OCLT of 1 or less. I will have a few days to be there to diagnose the system.

Is there a way to confirm the amount of Cl produced by a cell?

Thanks!

 

[chem geek]

Yes, you can determine your normal daily chlorine usage by turning off your SWG and manually chlorinating and noting how much chlorine you use to maintain the desired FC level. Then turn on your SWG and if it can't keep up even with 100% ontime and longer pump run times then fill in with manual additions of chlorine and after 24 hours the difference is your SWG output (factoring in %ontime and pump runtime).

The other way is to take a water sample directly from the return and note the higher FC level, but you need to know your flow rate and pool size (i.e. turnover rate) to figure out the chlorine output of the SWG cell. The IC20 is supposed to output 0.7 pounds of chlorine over 24 hours so in your situation with 100% ontime and the pump running for 24 hours then in 11,000 gallons this should be 7.6 ppm FC. I doubt very much that your daily chlorine usage is that high so your cell does seem that it is outputting a much lower amount.

As for iron, it's possible for more iron hydroxide to form at the hydrogen gas generation plate, but I'd be surprised if that is happening. It sounds like the cell may be old and nearing the end of its useful life. Oxides build up on the titanium under the coating (and on the coating) and restrict current flow which results in lower output. The IC20 presumably has a 10,000 hour life if ideally maintained so if normal chlorine usage were 2-3 ppm FC per day then that would be around 3-4 years of life. If you replace the cell, then as seen in Economics of Saltwater Chlorine Generators, it will be more economical to get an IC40 since it doesn't cost much more up-front but will last twice as long since you'll only run it with half the %ontime compared to the IC20.

 

[Sidecarist]

Thanks for the advice... I'm beginning to think testing the cell is a moot point. Just got home and even 24hr run @ 100% could only maintain fc of 1.5. I'll keep testing the water and learning this year, but will invest in a new cell next spring. The idea of the ic40 is interesting. I'll look into that.

I have learned a great deal and appreciate everyone's help and advice.

I'll enjoy our limited time this year with manual bleach usage an figure out how to deal with the iron staining. Next year will be MUCH easier!