How do I raise my TA?

[TexasGirl]

15000 Gal, gunite, Mineral Springs, BioGuard (Goldline) SWG, DE filter, negative edge and waterfall on separate pump and separate cartridge filter. Water looks very clear. Never an algae problem. Corrosion on nearby metal fence.


CL Residual: 3+ (Always high. I had CL generator turned down to 40%. Went to 30% today. I never shock. I never add chlorine)

PH: 8.2+ It’s always high.

Acid demand test: One drop. Chart calls for a bit more acid. I’ve been adding acid every week, trying to bring PH down.

TA: 60 (six drops) Always low.

CYA: 33 A bit low?

Salt: 3400 (compromised estimate. SWG readout says 3300. Test strips say 3500)


Is low TA my biggest problem? If so, should I add baking soda? How much should I start with?

Thank you!

 

[duraleigh]

15000 Gal, gunite, Mineral Springs, BioGuard (Goldline) SWG, DE filter, negative edge and waterfall on separate pump and separate cartridge filter. Water looks very clear. Never an algae problem. Corrosion on nearby metal fence.


CL Residual: 3+ (Always high. I had CL generator turned down to 40%. Went to 30% today. I never shock. I never add chlorine)

PH: 8.2+ It’s always high.

Acid demand test: One drop. Chart calls for a bit more acid. I’ve been adding acid every week, trying to bring PH down.

TA: 60 (six drops) Always low.

CYA: 33 A bit low?

Salt: 3400 (compromised estimate. SWG readout says 3300. Test strips say 3500)


Is low TA my biggest problem? If so, should I add baking soda? How much should I start with?

Thank you!

Hi, Debbie,

While your TA is low, I believe you should reduce pH first. SWG pools typically need constant acid added to keep pH down in the 7.2-7.6 range.

Have you downloaded bleachcalc? It's invaluable for how much to add for all your chemistry....pH and TA included. Once your pH is in line, you'll almost surely need a good bit of baking soda to bring your TA back up in the 90-120 range....bleachcalc will tell you how much.

Most SWG pools run pretty high CYA aorund 60-80. If you don't like messing with acid to lower your pH, you could put several pucks in the skimmer which will reduce pH and add CYA. You may have to turn off your SWG if you do that or you'll most likely overchlorinate.

The baking soda is easy to add and readily dissoves poured right into the skimmer....it'll change your TA with just a few hours of circulating.

Interesting comment about your corrosion on the fence....do you think it's coming in contact with pool water pretty often?

So.................in this order

1. Download bleachcalc

2. reduce pH

3. Increase TA

4. Consider increasing CYA

 

[JasonLion]

It would be nice to know your CH level.

A negative edge is going to provide a *lot* of aeration. That means that Co2 will tend to come out of soluton fairly quickly, raising the PH. If you look at the chart from Chem_Geek here you can see that you need to keep your PH relatively high and your ALK relatively low, which fits with the issues you are having.

Up to a point, low ALK is not as bad as high PH. If you aren't having any specific problems I would try to lower the PH by adding acid and allow the ALK to go down a little more. At the same time you need to do a quick check on your saturation index, which would be affected by this, but I would need to know your CH level to calculate that.

Long term you could try adding borates to buffer your PH so that you could lower your ALK even more. That takes some doing and has advantages and disadvantages. People say the water feels better. Your SWG efficency will improve. PH will be easier to maintain. But it takes lots of borax and acid to start, can be poisonous to pets if they drink much pool water, and it is illegal (or impolite) to backwash with too high a borate level in the water in some areas.

With a SWG I would try to raise your CYA level a bit. Different companies recommend different levels, something in the 60-80 range seems to work with all of them. A SWG will produce chlorine much more efficently at higher CYA levels and your losses to sunlight will go down a little.

 

[TexasGirl]

Thanks, Jason and Dave!

I downloaded bleachcalc. I dialed down my CL production, a bit. I'm getting my PH where it's supposed to be. After I get the PH corrected, I'll take another set of chemical measurements and get back to you with the results.

About 40% of my total pool edge is being aerated with either the negative edge or the waterfall, 12 hours per day. So, yes, I do have an unusual amount of aeration. The only thing I put into my pool regularly, is muriatic acid.

My fence "was" powder-coated steel. Spray from the negative edge (on windy days) rusts/corrodes the section of the fence nearest to the pool and only the side facing the pool. Fence guy says its the salt. Pool guy says its the chlorine. My landscaper sands/files it down to the metal every year, primes it and paints it with rust resistant primer and paint (2 day job). This problem is only on the pool spray side of the fence. Other side of same section is practically untouched. 75' of same fence away from the pool has no problems. It takes only a few weeks of occasional spray to begin the rusting process, again.

Thanks, again for your help!

 

[duraleigh]

Hi, Debbie,

The fence corrosion issue is a PITA, I'll bet. I'd put my money on the salt being the culprit. Poolsean, is there a fix for that problem?

PS - I don't know if I commented earlier, Debbie, but that view off your pool is as pretty as any I've seen. It was hard to tell where the pool quit and the lake began.