pH creeps up - too much aeration

[AnnaK]

First, the numbers:

FC maintained at 3 - 5 ppm
CYA = 30
ph ranges from 7.6 - 7.8
TA dropped from 100 to 80 over the past 4 weeks

The pool is being heavily aerated on a daily basis due to two German Shepherd dogs jumping in off the sides. They drag out large amounts of water and I refill approximately 2" every 3rd day.

Over the past several seasons I've kept the TA at 100 and the pH at 7.5 but with two dogs doing belly flops I'm having a terrible time maintaining those levels. I add some amount of HCl about once a week just to get the pH below 7.8 and that's not a problem. I mean, I'd rather not have to do that but will have to continue, I suppose.

Now the TA is dropping (why? from frequently refilling?) and to get it back to 100 I'll have to add baking soda and that, in turn, will raise the pH even more.

My questions:
1. Should I drop the pH to below 7.5 before I add baking soda to raise the TA?
2. Given the unavoidable aeration will this cycle (high pH - low TA) continue or is there something I can do to stabilize it?
3. I have some wiggle room with the CYA. Would it help if I increased my presently very low trichlor usage?

I would truly appreciate your thoughts on this.

 

[reebok]

why do you want to raise the TA?
pool-school/recommended_levels

 

[257WbyMag]

Anna,

Looking at your situation, if your TA is at 80, I think that raising the TA any more than it is would be counterproductive. In fact, you would probably benefit from a lower TA, say 70 ppm. I noticed a big difference when I took my TA from 80 ppm to 70 ppm. Also, I am sure that borates would help as well but since you have doggies who are in the pool a lot, that might not be a good idea although I don't think that it would be a problem unless they were drinking the water. But to be on the safe side, it is probably best to avoid borates.

Try getting the TA down a bit and see if that helps.

 

[AnnaK]

The TA is at 80 now, down from 100. I imagine it drops from the frequent refills we have to do. I'm concerned that if I let it drop more the pH buffering will be shot all to h***. Is that an incorrect evaluation?

I agree with not using borates. While the dogs don't drink pool water with that much jumping and fetching they do ingest quite a bit so it's not a compound I want to add if I can avoid it.

 

[257WbyMag]

What is the TA of your fill water? If it is very low, then frequent pool refills from the tap may be the culprit. Also, if you have been getting lots of rain, you can see a reduction in TA from that as well.

 

[JasonLion]

If you have a lot of aeration, you can let TA come down as low as 60, which will significantly reduce the PH increases.

 

[AnnaK]

From a lab test done on our fill water (treated well water) the numbers are:

pH 7.5
Alkalinity 80mg CaCO3/L = 80 ppm
Chloride 36mg/L = 36 ppm chloride, and I don't know how that translates to FC/CC/TC
Hardness 60mg CaCO3/L = 60 ppm
TDS 170
Corrosion index -0.93 sl corrosive - don't know what the sl stands for

Of the cations tested all were well below recommended drinking water levels except sodium which was at 45mg/L. This is true for inorganic trace metals as well. In fact, the lab guy said we should bottle and sell this water

Jason, thanks for the advice that I can allow TA to drop to 60. You've just stabilized my comfort level about a lower TA.

 

[anonapersona]

If your fill water is at 80 then I'd think you will tend to keep near that TA of 80.

(novice at pool chemistry however)

 

[AnnaK]

Not a bad analysis for a novice at pool chemistry

 

[mas985]

I add some amount of HCl about once a week just to get the pH below 7.8 and that's not a problem. I mean, I'd rather not have to do that but will have to continue, I suppose.

Now the TA is dropping (why? from frequently refilling?) and to get it back to 100 I'll have to add baking soda and that, in turn, will raise the pH even more.

The acid is probably what is lowering TA. I wouldn't worry about it unless it gets too low but what you will find is that the PH will not rise as fast when TA gets low so you won't be adding as much acid to control the PH and TA will stop droping as well. So things should start to stabilize at some point.

 

[AnnaK]

I was hugely comforted by Jason's comment that I can allow the TA to go to 60, echoed by 257's advice. I've always operated on the premise that a vinyl lined pool ought to be around 100 to 120 and I can't remember now why I thought that. Age does weird things to your thought processes. And other things.

Now that I can relax about numbers a little I can sit back and see what happens. Thanks, people!

 

[Butterfly]

Hi AnnaK,

Because you use a trichlor(limited) and bleach combo, you probably got the idea of TA of 100 to 120 from Recommended Levels in Pool School:

If you are using trichlor tablets for chlorine, follow the bleach recommendations but have TA around 100-120 and be sure it doesn't fall below 100.

So, there's nothing wrong with your thought process

 

[JasonLion]

The more trichlor you use, the more important it is for TA to be relatively high. To whatever extent you are using trichlor, keep an eye on the PH, and if it starts falling you will need to stop lowering TA. As long as PH is going up, then lowering TA should be fine.

 

[AnnaK]

Hi AnnaK,

Because you use a trichlor(limited) and bleach combo, you probably got the idea of TA of 100 to 120 from Recommended Levels in Pool School

Yep, that's it! Thank you for jogging my memory, I need all the help I can get

Ok, here's my plan now.

I've increased the setting on the inline chlorinator to a whopping 1/4 (up from 1/8). Talk about limited use of trichlor, huh? I'll wait and see what that does to the pH. The TA will likely stay around 80 since that's my fill water's TA. If the pH doesn't come down anytime soon I'll add muriatic and oh, getting that at Lowe's was an adventure!

Rather than hiking all over the store I asked a guy in Flooring. "Muri . . . uh, what? I'm sure we don't have that."
"It's used by tile layers and masons, for cleaning."
"Oh. Cleaning supplies. Yeah, down there past the dishwashers." And then, "Yo, Fred. We don't have, uh, murtatic acid, do we?" And Fred goes, "That's muriatic and it's with the cleaning supplies in aisle 5."

No, it's not. Aisle 5 has Windex and Oxyclean and garbage bags and smelly things but it doesn't have muriatic acid. The HD and the ACE are way far away from me so I decided to get pH Down at the pool store but just on a lark I asked the kid at the paint counter on my way out the store.

"Muriatic? Sure. It's right over here, come, I'll show you. Do you want the 31% or the 'green' version? What are you using it for?"

Now that's service!

Oh, and another thing. Walmart. Shopping for trichlor. They have trichlor with copper in the orange container or dichlor (or was that cal hypo?) in the yellow container. Lots and lots and LOTS of people buying granular shock. They did have two bags of baking soda but mostly it was bottles of this (will make your water sparkle) and jugs of that (will make your water feel silky smooth).

Today, the pool store got my money.

 

[AnnaK]

A quick update: all is well again. Last night's pH was at 7.5 again, TA at 80, FC at 4 with 0 CC. I had added 8 oz of muriatic in the morning and let the pump run during the day.

It may just be that I'll have to make more frequent acid additions now that the daily dog plunges are in full swing. It wasn't an issue last year because we only had one swimming dog then.