Target numbers to reduce rising pH?

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Poseidon

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May 24, 2007
148
Houston, Texas, USA
I was hoping someone could recommend some target numbers for TA (or anything else) that could reduce my pH rise. I use only sodium hypochlorite (10%) for chlorination. I have been intending to go with borates for quite some time now (and still may) but I just haven't done it. Besides, I have a really good aerator that I built myself which connects to the return, and I'm looking for an excuse to finally use it :-D .

My readings as of last night (all obtained with Taylor tests):
FC 3.0 (fas-dpd)
CC 0 (fas-dpd)
pH 7.5
TA 130
CH 130 (residual from my pre-BBB days. coming down gradually)
CYA <30 (I'm calling it 20 for now. added some cya a few days ago. will restest this weekend)

Many thanks ...
 
Chem geek has a chart that shows the outgassing ranges at various PH/Alk levels. Not sure where it is though.

Poseidon said:
I have a really good aerator that I built myself which connects to the return, and I'm looking for an excuse to finally use it :-D .
Click to expand...

How about a little more about this?

:)
 
Rangeball said:
Chem geek has a chart that shows the outgassing ranges at various PH/Alk levels. Not sure where it is though.

Poseidon said:
I have a really good aerator that I built myself which connects to the return, and I'm looking for an excuse to finally use it :-D .
Click to expand...

How about a little more about this?

:)
Click to expand...

I built it out of 1 1/2" PVC. I unscrew the eyeball return, and replace it with the aerator. I had to have the threads cut, but other than that, it was all home-made. Working in a manufacturing facility has it's benefits :-D . I'll try to post some pics tomorrow.
 
I generally recommend a TA of 80 to 90 when you are not using trichlor/dichlor. I know that several people have gone lower with some success. You can take it quite a bit lower, perhaps 50, if you add borates to 50 ppm. Also, people with plaster pools need to keep their saturation index in mind, perhaps raising calcium to compensate for the lower alkalinity.

It also helps to allow your PH to go up a bit, perhaps to 7.6 or 7.7. Of couse raising PH isn't such a great idea if you have issues with metals in the water.
 
Hi Poseidon
I cant tell you what to do but i will share my numbers to start i live in north Ohio it has ben dry this year and hot for Ohio 90 deg. now. pool is also at 88 deg. open to low numbers on everything so i had to work my way up. I opened on april 20. These are my numbers i just took them so i could pass them on to you.
FC 3.0
CC 0
PH 7.5 (This has bin rock solid and i have added no acid all year)
TA 90
CH 100
CYA 30
Borates 30( was going to go higher but this is working out well)
Hope this is some help to you
 
uncorrected TA between 70-90, pH 7.6 and lower it back down when it hits 7.8, CH around 250-300. This seems to work well for reducing acid consumption with unstabilized chlorine.
 
This chart shows the relative rate of carbon dioxide outgassing which will be proportional to the amount of acid you have to add over time (but not the pH rise or frequency of addition). As you can see, lowering the TA and raising the pH both have significant effects at reducing the rate of outgassing. The actual rate of outgassing will also be a function of aeration.

This chart shows the relative rate of pH rise. This takes into account the pH buffering effect from higher TA. So you can see that the effect of lowering TA on the rate of pH rise is small, but measurable while maintaining a higher pH has a more significant effect.

If you are using a hypochlorite source of chlorine (bleach, chlorinating liquid, Cal-Hypo, lithium hypochlorite) then you can have a rather low TA, but probably not lower than 50 ppm to play it safe (if you have Borates, as mentioned by previous posts, then that's better though Borates have more buffer capacity for a rise in pH and less for a large drop). Certainly if you ever use an acidic source such as Trichlor you have to be careful or increase your TA (to 100-120 or more if you will use Trichlor regularly).

Richard
 

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Thanks for the pics :) Awesome aeration action :) Curious, does your pump filter go up when you screw the aerator in?

My IG pool only has one return, so I've been apprehensive about building something that would limit circulation. I had been considering trying a venturi principle approach. Basicall, a 1.5" section of pvc with a T in the middle, which is screwed into my return (I have 1.5" pipe on all my runs), so the return flow is still fully flowing straight out for circulation. I would then reduce the T to maybe 1/2" or something and screw in a piece of PVC that would stick up above the pool surface. I'm wondering if this would allow the water rushing through the bigger pipe below to draw air via venturi suction, introducing it into the water as small little bubbles but not reducing the overall flow by any appreciable amount.

It's another thing on my "try this someday" list. Fortunately, rapid PH increase hasn't been a problem this season.
 
Rangeball said:
Thanks for the pics :) Awesome aeration action :) Curious, does your pump filter go up when you screw the aerator in?

My IG pool only has one return, so I've been apprehensive about building something that would limit circulation. I had been considering trying a venturi principle approach. Basicall, a 1.5" section of pvc with a T in the middle, which is screwed into my return (I have 1.5" pipe on all my runs), so the return flow is still fully flowing straight out for circulation. I would then reduce the T to maybe 1/2" or something and screw in a piece of PVC that would stick up above the pool surface. I'm wondering if this would allow the water rushing through the bigger pipe below to draw air via venturi suction, introducing it into the water as small little bubbles but not reducing the overall flow by any appreciable amount.

It's another thing on my "try this someday" list. Fortunately, rapid PH increase hasn't been a problem this season.
Click to expand...

No, my filter pressure does not change. My eyeball return has slots in it. I measured them and calculated the surface area. The holes in the aerator match the surface area of the eyeball slots. However scientific this may or may not be, the pressure is the same. Theoritically I should be pushing the same amount of water through.

I'm not sure I follow your idea, but it sounds interesting.
 
Poseidon said:
No, my filter pressure does not change. My eyeball return has slots in it. I measured them and calculated the surface area. The holes in the aerator match the surface area of the eyeball slots. However scientific this may or may not be, the pressure is the same. Theoritically I should be pushing the same amount of water through.
Click to expand...

Ahhh... Smart :) One of my ideas was to plumb something that would screw into my return, use a shallow elbow to get the end of the pipe above the water surface, and have a cap on it with several small holes drilled, enough to match the area of the return hole. I was thinking this would provide the same water volume and hopefully not impede circulation, but the smaller streams would create more and smaller bubbles :)

I'm not sure I follow your idea, but it sounds interesting.
Click to expand...

Imagine a piece of pipe that basically extends the return out into the pool a foot or so. Sticking straight up from it is a smaller piece of pipe that has the upper end above the surface of the water. Water flows through the larger pipe in the pool, and the flow creates suction in the smaller pipe, drawing air into the current.

.............Air
............. l
............. V

............. ||
..^^^^^||^^^^^^^^
_______||_______
-------->------>----->----->

Arrow is water flow. Air is sucked downward into water flow through vertical pipe. ^^^^^ is water surface. Ignore the "...", their to make the spacing work :)
 
I'm thinking it wouldn't. It should take the path of least resistance, and flow straight out.

It's based on the venturi principle, like a lot of suction intake devices are (chemical hose for running detergent through a power washer, for instance). In theory anyway.

Problem is I've has so few PH issues this year, I don't have a reason to try it :)
 
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