Water Chemistry and CYA for SWG pools

[rkgdmd]

Hi All,

We have a 29,000 gal vinyl pool with a SWG. I've been reading the Chemistry for SWG pools in the pool school forum, and I see a recommended level of CYA to be between 60 and 80. I currently have a level of 35. My cell output is set to 30%. FC has always been between 3 and 3.5 with this setting. Am I really looking for trouble by not raising the CYA when everything seems to be OK at these levels? Acid demand was about 1/2 gal week, but that seems to have dropped off. Also TA is now about 60. Am I headed for trouble?

Rob

 

[JohnT]

The only problem is that your cell life will be diminished running the lower CYA. It seems that the negatives of high CYA are mostly non-existent on a SWCG. Do you test your chlorine in the evening? How many hours a day do you run your pump?

 

[Guest]

This thread explains about the relationship between CYA, TA, acid demand, and why higher CYA levels are better for a SWG.
viewtopic.php?f=21&t=3663

Which make and model do you have, btw? Some manufacturers recommend CYA levels up to 100 ppm.

 

[rkgdmd]

SWCG is Aqualogic. I believe the recommended level of CYA is about 80. I run my pump 12 hours per day.... 8 A.M. to 8 P.M. I test the water about 7 A.M. My thinking was (quite possibly very flawed) I am able to maintain an adequate FC level with a relatively low cell output...seemed like a win-win situation. I've only been doing this 3 months and don't want to create a problem later on. Thanks!

Rob

 

[JasonLion]

What you are doing works obviously. But your current CYA level uses the cell more than you would need to use it at higher CYA levels. That is to say, at higher CYA levels you will be able to turn the percentage down even further. That means the cell will last longer and you will see smaller PH increases due to aeration if you raise the CYA level. If either of those issues are significant for you, try higher CYA levels.

 

[Guest]

SWCG is Aqualogic. I believe the recommended level of CYA is about 80. I run my pump 12 hours per day.... 8 A.M. to 8 P.M.

Rob

If your pump and filter are sized properly you can probably only run the pump for 8 hours a day if you increase the CYA. You will also probably be able to operate at a lower output percentage. The net effect will be less acid demand and longer cell life. There is a decided benefit to increasing the CYA with a SWG (and also adding borates to 50 ppm, which is why there are so many borate and salt/borate products on the market now).

You have to look at BOTH cell output AND pump run time. The cell will be on the same amount with a lower output and longer run time as it would with a higher output and shorter run time. Since the pump is the biggest electricity user it makes sense to use the shortest pump run time that will properly filter the pool and turn over the water. You might be on the money with your 12 hour run time but you might also be able to decrease it.
In any case I still recommend increasing your CYA to 70-80 ppm.

An acid demand of 1/2 gal/week is very high for a vinyl pool.

Is there a particular reason you want to run the CYA that low? If you are not installling ORP and pH controllers and electrodes then there is really no reason to keep it that low.

 

[rkgdmd]

No...I have no intelligent reason for the CYA to be at 35. It's just where it ended up after the pool was finished and the whole thing seemed to be working so I left it alone. I do intend to add the borates after reading your excellent posts concerning it's benefits....I'm just having trouble finding 23 boxes of 20 Mule Team....they already look at me kind of funny at the hardware store when I ask for 2 cases of acid at a time.

After discussing this with you and JasonLion, I think I may just be playing with fire and am going to raise the stabilizer level tommorow. Thank you both for your input.

Rob

BTW...pump is 1 1/2 hp Sta-Rite with 500 sq ft cartridge filter. All plumbing is 2 in. 2 bottom drains, 2 skimmers, 4 returns and an attatched 800 gal spa