High Alkalinity

[USAlover478]

I work on a 50,000 gallon pool. Our alkalinity has been between 120-140 for a couple of weeks now. I have done the calculations and put in nearly 32lbs. of sodium bisulfate to drop it. (This was put in as 8lb increments over a 4 day period). For the few days following this the alkalinity drops and is stable. Then it spikes up again, we have tested the incoming water and everything is stable. The pool was re-plastered just about a year ago. Having a hard time figuring out what could be causing this, any ideas are helpful! PH and everything else is balanced but not our alkalinity.

[Teapot1]

Once you have added the acid you need to aerate the pool water to raise the pH then add some more acid and aerate until you get it where you want it. Acid lowers the pH and correspondingly the TA but the water will draw the calcium from the plaster to raise the pH, you have to beat it to the point. Aeration raises the pH but leaves the TA where it is. If you have CYA stabiliser in the water the pH doesn't matter very much so allowing you to protect the plaster from erosion better.

[USAlover478]

Even when we have put in the Sodium Bisulfate the PH has remained constant and not lowered. How does one aerate a commercial pool exactly? My CPO class taught everything about chemicals and etc but I do not remember there being anything at all about aeration?

[USAlover478]

How does one aerate a pool? My CPO class did not entirely go over this to my knowledge. What is this supposed to accomplish once it is aerated? Just trying to get a better understanding.

Thank you

[Teapot1]

Yes with plaster pools if the pH lowers it returns by stripping the plaster natures way.
Have a look on youtube for pool aeration. I use a submersible pump modified to draw in air and aerate the water. As the bubbles break the surface the off gasing causes a rise in pH

[Phil.c]

Just curious, did you modify the submersible pump to draw in water and air or just air as some pumps need water to cool the bearings?

[Teapot1]

Water and air, its a water pump so wont draw in air. The modifiction just adds air to the water the same as an air leak does on a pool pump.

https://youtu.be/3Cj4-6nhNH4

[Phil.c]

So an extra air pipe added to the water inlet.

[Teapot1]

Watch the video, its why I posted the link.

[Phil.c]

Sorry, didn't see the link.

[Teapot1]

No problem.