Using lots of MA - Plaster still curing?

[Uncle Flappy]

Greetings TFP'ers! Quick question for y'all:

It's been almost 6 months since the re-plastering of my pool and I am still going through a significant amount of muriatic acid. Could the Pebble-Tec still be curing? Here are my numbers today:

Cl: 6
CC: .5 (Palo Verde pollen - ugh)
TA: 60
pH: 7.6
CYA: 80
CH: 300
NaCl: 2800 (but the SWCG reports 3100 )
​

In order to maintain pH, I need to add MA every 3-4 days even though I'm aerating the water very little. The spillover runs one hour per day with the VS pump at only 800rpm as not to create bubbles in the jets.

So - can I assume the plaster is still curing?

Thanks for the help!

- Flappy

 

[jblizzle]

I don't think it is the curing. Realize that a SWG is also aerating the water and driving up the pH. Having to add acid that often is fairly normal. Once the TA drops some more, the pH rise should show down.

Also the efficiency of your pump drops below about 1000rpm. Just a heads up.

 

[Uncle Flappy]

I don't think it is the curing. Realize that a SWG is also aerating the water and driving up the pH. Having to add acid that often is fairly normal. Once the TA drops some more, the pH rise should show down.

Thanks for the fast reply!

Any thoughts to the target TA? 60 seems fairly low - at least compared to Pool School Recommended Levels.

 

[jblizzle]

Mine is now around 50ppm and the pH seems to be staying below 8 for a few weeks.

Just keep an eye on the CSI since your CH is lower than mine.

 

[Uncle Flappy]

Also the efficiency of your pump drops below about 1000rpm. Just a heads up.

I appreciate the tip. If I can believe what the pump is telling me, energy consumption is roughly the same at 800rpm as it is at 1000. I chose the former to minimize aeration at the cost of efficiency. 800rpm isn't enough flow to create bubbles in the jets but 1000 is. The valve is too far from the automation system to install an actuator and I am too lazy to open and close it manually when using the spa. I just leave it open.

 

[Uncle Flappy]

Mine is now around 50ppm and the pH seems to be staying below 8 for a few weeks.

Just keep an eye on the CSI since your CH is lower than mine.

Cool beans, I will, thanks for your help. I may have to add some deicer if my CH keeps dropping. Oddly enough for Tucson, my well water is very low on calcium (50ppm).

 

[jblizzle]

Our well is around 130ppm. Evaporation causes the CH to rise about 125ppm a year. Up to 500ppm now.

 

[pooldv]

I appreciate the tip. If I can believe what the pump is telling me, energy consumption is roughly the same at 800rpm as it is at 1000. I chose the former to minimize aeration at the cost of efficiency. 800rpm isn't enough flow to create bubbles in the jets but 1000 is. The valve is too far from the automation system to install an actuator and I am too lazy to open and close it manually when using the spa. I just leave it open.

Might as well run it at 1000 rpm. I run mine at 1100 rpm for 150 watts. If your TA does drop to 50 ppm through additional acid additions then you might want to add some borates, it will help further stabilize PH More here, Borates - Why and How

 

[Chncdafied]

Remember a SWG will always slowly raise your pH. This is because one of the byproducts of a SWG is sodium hydroxide (NaOH), which has a pH of 12.

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[JoyfulNoise]

Remember a SWG will always slowly raise your pH. This is because one of the byproducts of a SWG is sodium hydroxide (NaOH), which has a pH of 12.

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This is not quite correct. The amount of OH- produced by an SWG would not cause the pH rise seen. And, like any chlorinating method (except for trichlor and dichlor), chlorine oxidation reactions are acidic (produces a proton, H+) and so any base added by chlorine is eventually balanced out.

What produces a pH rise from an SWG is the aeration caused by the production of hydrogen gas. The bubbling inside the cell causes CO2 to outgas from the water and that reaction consumes a proton as the bicarbonate alkalinity shifts in response to changes in equilibrium. It is that aeration that causes the net pH rise from an SWG.

Uncle Flappy,

How much acid are you adding and how often?

 

[Uncle Flappy]

Hey JN - good to hear from you. Before I had the plaster redone, my pH rose but at a much slower rate than it does now. I am adding roughly 32oz of MA per week. With my limited experience, that seems excessive - is it?
I just ordered some boric acid and will see if that makes a difference. I also ordered some calcium chloride to bring up the water hardness and help move the CSI index closer to neutral.

In doing some more research, I found the statement below in Pool School on the Start-Up New Plaster startup page (Pool School - Start-up New Plaster)

No matter what start-up procedure is used, your pool will consume a lot of acid during the first 6-12 months as the plaster finish continues to cure. It is important to test your pH daily and do not let it climb above 7.8. Be sure to continue to brush the pool at least weekly during this period

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Thanks for your help.

 

[JoyfulNoise]

32oz per week is not that bad actually. I use about 20 oz per week, maybe a little less and I have A LOT of aeration.

Definitely add borates, you'll be very happy with the results (but get your TA adjusted first!!)

Also, try to dose your acid so that your pH target is 7.6. Don't go lower than that. As well, wait until you get above 7.8 before adding any acid. With your magically soft water (seriously, your fill water is crazy soft considering you live in Tucson!), you can easily wait until your pH is close to 8 before adjusting.

I'm getting the Big Green Egg ready for some serious smoking this summer. I've got three full racks of St. Louis style pork ribs ready to make some great pig-candy. Family will be visiting in late May so I'm shopping for nice pork-butt (bone in) and we will probably do a beef brisket. I need to pick up another bag of hardwood charcoal this weekend.

 

[Uncle Flappy]

Thanks, JN. Just so I am clear, what should be my target TA? Right now it is 60 and pH is 7.6.

I like your style - we too are having a family reunion in June. Porkcicles and Boston Butt are definitely on the menu. Man, I am salivating already.

 

[JoyfulNoise]

Thanks, JN. Just so I am clear, what should be my target TA? Right now it is 60 and pH is 7.6.

I like your style - we too are having a family reunion in June. Porkcicles and Boston Butt are definitely on the menu. Man, I am salivating already.

60 is fine for now. When you get borates in the water you can take it down to 50ppm but I'm not sure it will stay there. It all depends on evaporation and fill water. My water seems to like to hang at 60-70ppm TA and not go any lower. I can certainly lower it but then I have to add more acid to keep it that way. 60ppm TA is a happy medium for my pool. A pH target of 7.6 is very manageable and should be fine.

 

[Uncle Flappy]

I got my boric acid today and added enough to bring levels just under 50ppm. It did lower pH just a tad.
Now I need to better balance my water so that it isn't so corrosive.

FC 6
CC 0
pH 7.5
TA 60
CYA 80
CH 350
Salt: 3000
Borates 50
Pool temp: 75

CSI: -0.63
​

What levels need to be increased or should I just kick back and let the pH (and water temperature) naturally rise?

Thanks for the help.

- Flappy

 

[JoyfulNoise]

Let your pH come up and do not go lower than 7.6. That will have a big effect. Also, the CSI gets more positive as the temperature increases. You could also let your alkalinity go up to 70ppm. CH will drift up naturally as time goes on.

 

[Uncle Flappy]

Thanks, Matt. If I understand you correctly, I shouldn't add anything and just let the pH and MA rise on their own, correct? The way pH histocially has been rising, it will only be a couple of days before it is at or above 7.6.

- Bill

 

[JoyfulNoise]

Thanks, Matt. If I understand you correctly, I shouldn't add anything and just let the pH and MA rise on their own, correct? The way pH histocially has been rising, it will only be a couple of days before it is at or above 7.6.

- Bill

Yup. It'll come up on its own. You should see it rise more slowly and "stick" at some higher value. My pH tends to stick at 7.7-7.8 and won't budge for a week or more. You can help increase the pH by doing lots of cannonballs too

 

[Uncle Flappy]

...You can help increase the pH by doing lots of cannonballs too

Ha!!! I am better at belly flops (larger surface area).

Thanks again for all your help, JN, I greatly appreciate it.

 

[JoyfulNoise]

No problem. Post back and let us know how your acid demand changes. Also, see if you get an FC boost from your SWG; sometimes adding borates improves the efficiency of the salt water cell by helping to limit algae growth and thus lowering the burden on the cell. I know when I added borates the first time my FC jumped from 7ppm to almost 9.5ppm and I was able to dial back my SWG output. Doesn't always happen but sometimes it does.