SWCG may be causing chemistry problems?

[Heavyhook]

I installed a Circupool RJ-20 SWCG system rated for 20K gallon pools at the beginning of the 2012 season. I have a Doughboy 16X32 AGP with a 19" sand filter powered by a 1-1/2hp Hayward Power flow pump. I belive the pump is rated at 80 GPM? During last season I ran the pump WCG at 50% for 10 hours per day and maintained 7ppm all season long.
I usually get the pool up and running around May 1st each year. This because of warmer weather I experenced a alge bloom around March 1st. I added 4.5 gallons chlorine brushed the pool and it cleared up. 3 weeks later I had another large alge bloom one week before I had my system up and running. I waited until my system was running the next week to let the SWCG deal with the second bloom.
After starting up my system running the pump 24 hour a day and the SWCG @ 100 for 3 days while brushing the pool twice a day. The pool cleared up nicely and I reduced my pump operation to 12 hours daily and the SWCG 10 hours daily running at 100% output. Its been running like this for 3 weeks now. My PH is through the Roof!as high as the test kit will read. I added 1 gallon of Murtic acid a week ago and that brought my PH down to 7.5 . I thought things were going great then now in one week its at 8.0+ again. I have continued to run the SWCG at 100% for 10 hours a day because my DPD tests show only 1 to 1.5 ppm CL. I have a clear generator cell and the plates are tarnished but don't seem to have any buildup on them. I have never acid washed the cell. I took a water sample directly from the water return port and the DPD test showed 5 ppm CL. I can see the generator gassing through the clear cell enclosure and that seems normal. My pool is sparkling clear so whats using my CL up? Could there be alge still alive inside my sand filter using the avaiable CL up. The CYA tested at 40 ppm yesterday. Is running my SWCG @ 100% 10 hours per day the reason I cannot get my PH to stablize around 7.4 ? Should I use liquid bleach at shock level of 10ppm for 72 hours to kill what ever is using my avaiable CL ?
I just don't know which direction to attack this problem? Thanks for any ideas you may have in this!

[waste]

Hey Heavyhook

My initial thought is that you are running the SWCG too high

In the process of turning saline water into chlorine, there is an extra hydrogen atom that has nothing to bond with, so it becomes gas and the aeration causes the pH to rise (do you see little bubbles coming out of the return?)

I'd say to reduce the SWCG output to 50% and use bleach to augment when needed.

A full set of chem #s would also help

[Heavyhook]

I completely shut down my SWCG in a attempt to stabilize the chlorine and PH levels. Then reintroduce the SWCG's Chlorine slowly and monitor my water chemistry to see how its coming along. Here's the test numbers you requested. Testing done using Taylor K2005c and Fas-DPD kit for CL, Borate test strips for Borax. Opened May 1st this year no bather load as of this post yet!
5-23-13 Shut down SWCG system @ 7:00pm. water test were FC=1.5ppm, CC=0.0, PH 8++ , CYA 40 ppm added 142oz bottle 6% Bleach new FC=6.0ppm
5-26-13 12:00pm FC=0.0ppm CC=0.0ppm added 142 oz.'s 8.25% Bleach. @ 4:00pm PH 8++ added 1 gallon Muriatic Acid. 9:00pm test results FC=3.4ppm, CC=0.0, CYA=40ppm, PH=7.4, TA=220ppm ,CH=60ppm,
Borax 30ppm
5-27-13 8:00am FC=3.4ppm, CC=0.0, PH =7.2 Taylors Watergram dial chart indicates my Saturation index to be at 0.55 .
After installing the SWCG at the beginning of the 2012 season I started experiencing scaling deposits mainly on the bottom of the liner. At the beginning of this year after initially treating for a sever algae out break and vacuuming out the left over debris the liner was spotless. But has slowly started building up scale deposits on the liner and now is now spread across a large portion of the bottom. Could this be coming from my high
TA=220ppm? I am not really sure how to deal with that other than do a complete water change on the pool?
I have to be out of town for 4 days starting tomorrow. Since I cannot continue just on bleach at this time I am considering adding one more bottle of 142oz's of bleach in the morning and starting back up my SWCG and running at the 50% level you suggested. I have been running my filter pump 12 hours per day and had previously run the SWCG 10 hours per day. Should I keep the SWCG on that many hours to start with and then go from their? Since this a Holiday I do not expect a replay today. I will be back home next Saturday so the system will be running on auto @ 50% for 4 days until I return. Thanks in advance for your help and any guidance you can offer me!

[Heavyhook]

I posted the info Whizbang Spinner requested a week ago but haven't had a response at this point. We have just gone through a very busy holiday weekend and I know folks have a lot going on in their lives besides this forum. If their is another PF Support Team that would care to give me some guidance on my current problem I would be very grateful. Thanks!

[chem geek]

Your high TA is the primary cause for your fast pH rise and at higher pH and TA you are probably getting calcium carbonate scaling in your SWCG cell in spite of the low CH. At pH 8.0, the saturation index is +0.2. The borates help to reduce the problem, but are not enough given your high TA. The good news is that you have no overnight chlorine loss which means you don't have anything consuming chlorine in your pool like algae or organics.

Test your tap water to see the TA and if it's a lot lower then the pool then some water replacement will help, but you can also accelerate the lowering of TA by following the "add acid and aerate at low pH" procedure described the Lowering Swimming Pool Alkalinity -- A Step by Step Guide. It's going to take a lot of acid to get your TA down -- every gallon of full-strength Muriatic Acid (31.45% Hydrochloric Acid) will lower your TA by 40 ppm but you won't add these all at once. You follow the procedure to lower the pH to around 7.0 and keep it there while aerating.

[Heavyhook]

I have aerating 24 hours round the clock form a strong jet from my filter return aimed at the surface. My tap water test are PH 8+, CH 10ppm, TA 260ppm. Our water is supplied from local wells. Our bedrock is limestone not far below the surface. At 7:30 am this morning water test were FC 3.5ppm, CC 0 ppm, PH 8.0 , Acid demand 5 drops to 7.6 ph, TA 100ppm, CH 60ppm, added 121 oz's 8.25% bleach.
My TA & CH are dropping as you anticipated. My scaling on the liner has been reduced by 75% so far. I have been adding 32 oz's of 31.45% Muriatic Acid daily. If I understand the Lowering Swimming Pool Alkalinity -- A Step by Step Guide correctly my PH needs to come down to 7.0 then be allowed to rise to its natural level. When should I start to see the PH drop? Do I need to increase the volume of Muriatic Acid daily since the TA has reached the target level of 100ppm to get the PH to drop now? Do I need to stop aerating ? Am I assuming right that I stay on bleach with SWCG off until all the water chemistry numbers are where we want them?
Also I looked back in my notes to 3 years ago when I changed the water in my pool. I had added 16 pounds of Calcium before I found the PoolForum and discovered it was not necessary with a vinyl liner pool!

[BigDave]

Since you have a SWCG, you might go a little lower with the TA.

Adding the Acid will bring the pH down directly (TA too). The aerating is to bring the pH up (without increasing TA) after reducing it with acid; when your pH and TA are where you want them, stop aerating.

You can always use bleach for chlorination. When you do resume operating the SWCG, pH will probably start to rise - use acid to keep it where you want it.

[Heavyhook]

Chem Geek recommended aerating and following directions from Pool Doc in "Lowering Swimming Pool Alkalinity -- A Step by Step Guide" which includes the following,


"If your CA / TA level is not what you need to be, then you keep adding acid, so the pH will stay down:
. . . so the lost carbonic acid will keep being replaced with newly converted carbonic acid
. . . so the CO2 will keep gassing off
. . . so the CA will keep dropping.

When your CA gets where you want it, just stop adding acid, but keep aerating till the pH returns to the 'normal' level.

Ben
PoolDoc"

My PH levels have never dropped during the time I have been reducing the TA and CH levels. This may be where I am getting off track. Pool Doc and Chem Geek say to keep aerating, and my understanding was that doing so during SWCG operation would help GAS OFF the CO2 created by the electrolysis process to help prevent the PH rising. Don't at some point I need to add enough acid to drop my PH to near the lowest level of my test kit recommended in "Lowering Swimming Pool Alkalinity -- A Step by Step Guide" ?

[kelemvor]

Yes, you need to be adding acid and testing pH often to keep the pH low while you aerate. Only when you're done do you need to let the pH rise back up.

The more often you can manage to test and adjust, the better it will likely go.

Something else worth mentioning. You can increase the CYA to 60ppm and reduce some of the chlorine loss due to sunlight. In Texas, it probably beats down just like it does for me here in FL. The circupool user guide recommends 30-60 CYA - I'd go 60. Also, the 7ppm fc is a little high of a target with a swcg. You really only need to be between 1-3. Lowering the output on your swcg to target this range will help keep pH climb in check too.

[BigDave]

Since you've reached your TA goal without ever getting the pH into the low end, finishing the TA reduction process will be a little different for your pool. Stop aerating and add acid until your pH is where you want it.