I need some opinion / advice from the experts here. . . (chem geek - I hope you are reading this)
OK - I went to see a public indoor pool today ( 250.000 gal) in order to take a look at their filtration system.
Filters are old, rusty and they are thinking of replacing them.
Crystal clear water ( 0.12 NTU ) ph=7.55 FC = 1.81 TC=2 TDS= 1180 TA= 100
Pool is well kept - Staff follows recommendations of the CPO Handbook. . .
Sodium Hypochlorite as a Chlorine donor , Hydrochloric Acid ( 22 Baume) for lowering the ph is used.
Now - I asked the guy how much acid he is using since I saw quite a few drums (50 gal) in the filtration room.
He is averaging about 6 gal / day , which I find quite a lot. . .
In order to keep his TA at 100 ppm he naturally uses quite a lot of Sodium Bicarbonate as well (average 20 lbs / day)
So - here I saw a typical "yo yo game" scenario. Sodium Bicarbonate -> pH up , compensate with Acid -> ph and TA down.
Basically he is "fighting" one thing with another one.
He puts about every 2nd day the Sodium Bicarbonate straight into the Pool.
I suggested to pre-mix the Sodium Bicarbonate in a container ( proportion of 10 parts of water to 1 part of Sodium Bicarbonate)in the filtration room and inject this solution with a small metering pump slowly and continuously after the filters so it goes evenly into the swimming pool until he reaches his desired TA. While doing so he should turn off his Acid pump till all the water is well distributed.
Theory behind this approach is to avoid those spikes he's got now with wild fluctuating swings in pH and TA.
I also anticipate quite a reduction in both Acid and Sodium Bicarbonate consumption.
Naturally his supplier sells him Sodium Hypochlorite , Acid and Sodium Bicarbonate and more or less tells them that it's going to be the end of the world
and catastrophic consequences will happen if his TA drops below 90 ppm and the pH drops below 7.5. . . lol
According to my experience I've never seen any problems even if the TA drops down to 50 ppm.
Ideally I want them to run at a pH of 7.3 max - if they want to keep the TA at 100 it's fine with me too.
FC levels should be max. 1 ppm (as long as we are able to keep the ORP's at around 750mV. . . (chem geek - you knew this would come. . lol
Question : I know it is simply not possible (unfortunately we got this law of nature / chemistry) to decrease the pH by not decreasing the TA,
but which would be the smartest way to avoid this "yo yo game" as much as possible ?
Thanks in advance