Unique problem with lowering TA

[mzuniga]

Hello everyone. TFP has been an amazing resource to me over almost 2 years of pool ownership and I religiously follow the advice provided here. However I have to make a few adjustments here and there because my specific setup (SWGC and CO2 injection) and the fact that I live in Costa Rica where a lot of things you can buy at a Home Depot in the US are not easily found here. On the other hand, my pool is open year round so there's a huge silver lining.

That been said, and as usual with my setup, my TA drift upwards throughout the year. I start with a TA of 60 and after three or four months it has drifted to 150 or so, so I need to do the whole add MA and aireate until I get it back to 60. So there is the issue: on one hand our MA seem to have a lower concentration than indicated in the label so I end up having to add as much as 10-15 gallons during the process and also the liquid is yellow in color, probably from artificial coloring added to it. So my water end up yellow-tinged for a month or so. I've tried to find some sort of industrial use MA without the yellow coloring to no avail

My question is if this would be a situation where I can use Dry Acid as Sodium Bisulfate I can buy in bulk here. I know about all the cons about it, particularly in plaster and SWGC pools but I would only be using it four times a year. Would I be a terrible idea to use it in that context? Please do chime in and thanks in advance.

 

[PoolStored]

Hello everyone. TFP has been an amazing resource to me over almost 2 years of pool ownership and I religiously follow the advice provided here. However I have to make a few adjustments here and there because my specific setup (SWGC and CO2 injection) and the fact that I live in Costa Rica where a lot of things you can buy at a Home Depot in the US are not easily found here. On the other hand, my pool is open year round so there's a huge silver lining.

That been said, and as usual with my setup, my TA drift upwards throughout the year. I start with a TA of 60 and after three or four months it has drifted to 150 or so, so I need to do the whole add MA and aireate until I get it back to 60. So there is the issue: on one hand our MA seem to have a lower concentration than indicated in the label so I end up having to add as much as 10-15 gallons during the process and also the liquid is yellow in color, probably from artificial coloring added to it. So my water end up yellow-tinged for a month or so. I've tried to find some sort of industrial use MA without the yellow coloring to no avail

My question is if this would be a situation where I can use Dry Acid as Sodium Bisulfate I can buy in bulk here. I know about all the cons about it, particularly in plaster and SWGC pools but I would only be using it four times a year. Would I be a terrible idea to use it in that context? Please do chime in and thanks in advance.

Yeah, it is not a great idea.

Looks like your acid is 29.5%. 10 Gallons would lower the equivalent of 17.0 pH. Each POUND of dry acid would lower the equivalent of .2ph. You would be adding a lot of dry acid.

Once you add them, sulfates do not go away. See the thread Sulfates why so bad? and Sulfates - what's the problem?. You will see sources that say that sulfates at around 300 ppm become an issue for plaster. There is no way to reasonably test sulfate levels, and the only way to get rid of them is to replace water. There is also this paper that describes the far greater recrystallization pressure from magnesium sulfate compared to magnesium chloride for splash-out that could affect stone and concrete surfaces. I'd stick with the Muriatico...or try to find some without dye.

 

[Texas Splash]

I'm wondering why that gorgeous avatar pic wasn't one of our recent Pool of the Month (Scenic Views) nominees?

 

[Newdude]

I'm wondering why that gorgeous avatar pic wasn't one of our recent Pool of the Month (Scenic Views) nominees?

I'll go on record for saying that rainbows qualify for 'unique features' for this month's contest.

 

[mzuniga]

Thanks @Newdude and @Texas Splash. Believe it or not this photo was taken just a couple days after we inaugurated our pool and amazingly there was no Photoshop involved!

 

[proavia]

Yeah, stay away from dry acid - especially with the SWG.

Is it possible to not allow your TA to rise 80 points before taking action to lower it back down to 70?
Maybe try lowering with MA when it rises to 100-110. This would introduce less dye at one time and the color might not be as obvious in the water or may dissipate quicker.

 

[mzuniga]

Yeah, stay away from dry acid - especially with the SWG.

Is it possible to not allow your TA to rise 80 points before taking action to lower it back down to 70?
Maybe try lowering with MA when it rises to 100-110. This would introduce less dye at one time and the color might not be as obvious in the water or may dissipate quicker.

Yeah, that's the thing. TA bounce back up fairly quickly so I would be adding acid every few weeks defeating the purpose of the CO2 system. I can't still figure out why my TA bounces up so fast. I'm sure is not the water as I have tested both the filling and the rain water and TA is no more than 90.

 

[mknauss]

Alkalinity is either from the fill water or you are adding it chemically. No other source.

 

[mzuniga]

Hmm, @mknauss, so I'm sure is not the fill water or the rain. Chemically I'm adding salt, CO2, CYA, calcium chloride and boric acid as needed. Nothing else going into the pool. So nothing in that should be raising TA that I know of right?

 

[mknauss]

None of those items will add appreciable alkalinity.