3 months after plaster going through 13 oz of acid a day, normal?

Jump to latest Follow Reply
With your fill TA level and the extreme evaporation you experience, you will always be adding acid regardless of where your pool's TA resides. Certainly lowering the TA will be a great improvement, but at the cost of adding calcium, is not worth it.

With as high as your fill water is in calcium, you'll need to be very familiar with the CSI and how each parameter effects the end result...might as well start now. The recommended levels work great for those that open/close and drain their pool every year but that isn't the case in your situation. As previously mentioned, targeting a pH in the 7.6-7.8 range will get your CSI back where it should be, and even with a TA around 60-70, your CSI is around -0.36 to -0.45 (with rough numbers from above). When using the acid/aeration method to lower the TA, your CSI will be low since you must drop the pH to do so. This is only temporary and shouldn't be a concern. You need to focus more on where the CSI will be long term.

PH by far has the biggest impact on CSI, TA is second. Calcium takes large swings to show any effect. Plug fictitious numbers into the calculator and experiment with how the CSI changes.
 
So I've been stressing about my CSI, it was in the less than -0.6 range for about 24 hours, I'm now sitting at -0.6 and improving as I run my water features. Did I harm my plaster during that 24 hour period?


Sent from my iPad using Tapatalk
 
No. It takes a lot longer to dissolve plaster from a low CSI particularly if the pH is not very low. There are pools that use Trichlor pucks where the owner doesn't test and the TA gets to 0 and the pH crashes to 4.5 or below and in those situations that exist for an extended period of time the plaster can be seriously degraded and copper heat exchangers damaged as well.

You don't want to go an entire season or for months on end with a low CSI (i.e. -0.7 or so), but 24 hours is no problem. Tests were done with plaster coupons where degradation was seen at -0.7 over months.

Technically, a -0.3 CSI means that there is HALF the amount of calcium or carbonate or their product of concentrations compared to the amount needed for saturation. A -0.6 CSI means that there is ONE-FOURTH the amount compared to saturation. It's a logarithmic scale so small changes in the number represent significant changes in the saturation of calcium carbonate in the water.
 
chem geek said:
No. It takes a lot longer to dissolve plaster from a low CSI particularly if the pH is not very low. There are pools that use Trichlor pucks where the owner doesn't test and the TA gets to 0 and the pH crashes to 4.5 or below and in those situations that exist for an extended period of time the plaster can be seriously degraded and copper heat exchangers damaged as well.

You don't want to go an entire season or for months on end with a low CSI (i.e. -0.7 or so), but 24 hours is no problem. Tests were done with plaster coupons where degradation was seen at -0.7 over months.

Technically, a -0.3 CSI means that there is HALF the amount of calcium or carbonate or their product of concentrations compared to the amount needed for saturation. A -0.6 CSI means that there is ONE-FOURTH the amount compared to saturation. It's a logarithmic scale so small changes in the number represent significant changes in the saturation of calcium carbonate in the water.
Click to expand...
Thanks chem geek, like I said I was a bit stressed there, didn't think that 24 hours in that range could cause a lot of damage but wasn't sure.

Here are my numbers this morning:
FC 4.5
CC 0
pH 7.5
TA 80
CH 290
CYA 70
CSI - -0.46​

Feeling much better about these numbers. Will play with them to get my CSI closer to -0.2 to -.01ish which means a target pH of 7.7 and TA 100. Sound like a plan?

Thanks for walking me through this one guys!
 
This may or may not be related, however, since I've never seen this I thought I'd post it.

I was brushing my benches off this morning and noticed a white nickle size "wafer" sitting on my bench. I reached down to grab it and when I touch it it broke apart. Think this was related? As I said I've never seen anything like this before.

EDIT: Did some searching and from what I can tell it's probably from my SWG running a self cleaning from what I can tell.
 
Yes your plan sounds fine. Your TA and CH will rise over time with evaporation and refill.

And yes, that may be a calcium carbonate flake that was sloughed off of the SWG plate when it reversed polarity. This is why you'll want to target a slightly negative CSI (around -0.2) to help prevent such scaling. The use of 50 ppm Borates also helps a lot with that.
 
chem geek said:
Yes your plan sounds fine. Your TA and CH will rise over time with evaporation and refill.

And yes, that may be a calcium carbonate flake that was sloughed off of the SWG plate when it reversed polarity. This is why you'll want to target a slightly negative CSI (around -0.2) to help prevent such scaling. The use of 50 ppm Borates also helps a lot with that.
Click to expand...
So you would recommend borates? Would you recommend introducing this late in the season, I'll be removing my SWG at the end of October or introduce them next spring?
 
trbvm said:
Why would you remove the SWG in Oct and put it back in next spring? I am in AZ, same weather as you... Is it recommended to remove SWG during winter?
Click to expand...
My understanding is the SWG will not produce chlorine under 52 degrees. From November - February my pool water will be below this so I'm going to disconnect, put in my dummy cell for the winter. I'm sure I could get away with leaving it in but also won't hurt to remove it.
 

Enjoying this content?

Support TFP with a donation.

Give Support
I leave mine in as I can usually get the water above the 52F mark by late afternoon with a good sunny day. There's only maybe a month or two down here where the water temps will remain below 52F consistently so I'd rather not fiddle with disconnecting the unit.

Just remember to stay on top of FC checks. Even though the loss rate will be quite low, I found that I needed to add bleach last winter as the SWG was not running enough to keep the FC at an adequate level. You still get loss from sunlight and organics blowing in.....and any members of the local Polar Bear Club looking for a pool to dip in ;)


Sent from my iPhone using Tapatalk
 
QingGuy said:
So you would recommend borates? Would you recommend introducing this late in the season, I'll be removing my SWG at the end of October or introduce them next spring?
Click to expand...

I will also speak highly of 50 ppm of borates (boric acid preferably), but keep in mind that this will lower your CSI further (by a surprising amount). Make sure you know what that's going to do to your CSI and be prepared for it when the time comes.

I too would leave the SWG in place year round. No need to remove it.
 
Thanks, guys.. I am planning on keeping the pool heated at 80 ... with the autocover, I should see minimal heat loss and the heat pump should keep my costs low.
Hopefully, I will delve into the mysteries of borates next spring!
 
bdavis466 said:
I will also speak highly of 50 ppm of borates (boric acid preferably), but keep in mind that this will lower your CSI further (by a surprising amount).
Click to expand...

Adding 50 ppm Borates using boric acid lowers the pH some (about 0.2 units if one starts at pH 7.5; about 0.4 units if one starts with pH 7.8), but once one adjusts the pH back to where it was the CSI after the borates addition only drops by 0.04 at pH 7.5 or 0.09 at pH 7.8. The change is due to boric acid being a weak acid and if you use aeration to restore the pH back up then you've essentially lowered the carbonate alkalinity by 6 ppm at pH 7.5 or by 11 ppm at pH 7.8.
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply