Nitro's Approach To Water Maintaince

[keith55]

What is aeration doing chemically to increase pH?

Thanks

[LauraG]

I just can't thank you enough (again) for all of your time and help. I've just got to tell you that you have no idea how much your help (and Nitro's too ) means to me. I am learning so much and I'm actually enjoying it. I promise that I will be more dedicated to the exact measurments. You might not like this, but I did add one teaspoon of pH up just to help me out, as the areating for over an hour did bring up the pH, but not enough IMHO.

It's funny that you mentioned another site as I was going to ask you about that. Would you rather I started posting my test results there instead of here? This site does make me nervous after last weekend.

You are most welcome. You can continue to post here for now, but my "home" is really at Trouble Free Pool (TFP) and if this site continues with the spam posts I'll probably be leaving. If you want to move to TFP you are certainly welcome to and there are others there who can help you -- Nitro has signed up over there and waterbear has always been there (he used to post here more frequently).

Richard, the pH was still 7.0 so, I added just one teaspoon pH up and aerated for an hour, now it's 7.8. I am developing a yellowy brownish stain around the water line, and I can't scrub it off. This was before the 7.8 pH, although I have no idea if this is a factor.

[Nitro]

So was this past 2 months Dichlor then bleach or did you start out with it as Dichlor only? Definitely keep us posted on how it goes from here -- most people who've tried Dichlor then bleach get about double the length of time before water replacement and their water isn't as noticeably funky either. Of course, it depends on how clean one is when using the tub since some oils and lotions will build up even using chlorine properly.

I used Dichlor then bleach. My CYA was 30 ppm. However, I don't know if you remember, but this was a new tub. I believe that's the reason my water didn't last very long. Also, I had quite a few bathers in there the first few weeks. BTW, I used a Spa Flush to clean out the pipes, and it did produce some yellow gunk/foam. I'm hoping to get 4 months out of this fill.

[Nitro]

Richard, the pH was still 7.0 so, I added just one teaspoon pH up and aerated for an hour, now it's 7.8. I am developing a yellowy brownish stain around the water line, and I can't scrub it off. This was before the 7.8 pH, although I have no idea if this is a factor.

Is that a stain, or is it more of a film? Is it slippery to the touch? Try putting a little Baking Soda on a wet rag and wipe it off. Careful with the BS, because it will raise your TA if you use too much.

[chem geek]

What is aeration doing chemically to increase pH?

Thanks

It's removing carbon dioxide from the water via outgassing that is accelerated when there is more aeration or when the pH is lower. Pool and spa water is intentionally over-carbonated in order to provide a pH buffer and to provide carbonate for calcium carbonate saturation (to prevent dissolving of plaster/grout/gunite). There is an equilibrium between the carbonate species in the water as follows:

CO₂(aq) <---> CO₂(g)

Carbon Dioxide dissolved in water <---> Carbon Dioxide gas in air

H₂CO₃ <---> CO₂(aq) + H₂O

Carbonic Acid <---> Carbon Dioxide dissolved in water + Water

HCO₃^- + H⁺ <---> H₂CO₃

Bicarbonate Ion + Hydrogen Ion <---> Carbonic Acid

CO₃^2- + H⁺ <---> HCO₃^-

Carbonate Ion + Hydrogen Ion <---> Bicarbonate Ion

Though that's a lot of equations, the dominant species are carbon dioxide dissolved in water and bicarbonate ion so the simpler way to look at it is as follows:

HCO₃^- + H⁺ <---> CO₂(aq) + H₂O

Bicarbonate Ion + Hydrogen Ion <---> Carbon Dioxide dissolved in water + Water

When carbon dioxide leaves the water, that lowers the concentration of carbon dioxide on the right side of the above equation. That has the equation move to the right so Bicarbonate Ion combines with Hydrogen Ion to make more dissolved Carbon Dioxide. pH is a negative logarithmic measure of the amount of hydrogen ion so since the above reduces the amount of hydrogen ion this raises the pH (water becomes more basic or alkaline; lower in hydrogen ion).

Technically, the Total Alkalinity (TA) does not change because though bicarbonate ion adds to TA, Hydrogen Ion subtracts from TA. Since both bicarbonate ion and hydrogen ion are lowered in concentration from the above reaction, there is no net change in TA. TA is a measure of any species that can except a hydrogen ion, but subtracts hydrogen ion itself. The TA test actually measures any species that can accept a hydrogen ion down to a pH of about 4.5 which is when the indicator in the TA test changes color. Clearly, if the hydrogen ion concentration is already higher so that the pH is lower, then this makes the TA lower since you are closer to the 4.5 pH when the test says it is done.

Richard

[LauraG]

Richard, the pH was still 7.0 so, I added just one teaspoon pH up and aerated for an hour, now it's 7.8. I am developing a yellowy brownish stain around the water line, and I can't scrub it off. This was before the 7.8 pH, although I have no idea if this is a factor.

Is that a stain, or is it more of a film? Is it slippery to the touch? Try putting a little Baking Soda on a wet rag and wipe it off. Careful with the BS, because it will raise your TA if you use too much.

It is a stain for sure, and not slippery to the touch. I will carefully wipe with the BS. Thanks.

[Nitro]

Well I got my CH up to 200 ppm, finally. It took 8 oz (volume) to go from 100 to 200 in my 320 gal tub. That's way more then I calculated (4 oz using ThePoolCalc). I wonder if the Calcium I have is a lower percentage. It doesn't say on it. Is there anyway to find out?

[chem geek]

Well I got my CH up to 200 ppm, finally. It took 8 oz (volume) to go from 100 to 200 in my 320 gal tub. That's way more then I calculated (4 oz using ThePoolCalc). I wonder if the Calcium I have is a lower percentage. It doesn't say on it. Is there anyway to find out?

To go from 100 to 200 ppm CH in 320 gallons would take 4.7 ounces weight (around 3.8 ounces volume) of Calcium Chloride Anhydrous, but would take 6.3 ounces weight (around 7.2 ounces volume) of Calcium Chloride Dihydrate. I suspect that you have the dihydrate form of Calcium Chloride.

[Nitro]

To go from 100 to 200 ppm CH in 320 gallons would take 4.7 ounces weight (around 3.8 ounces volume) of Calcium Chloride Anhydrous, but would take 6.3 ounces weight (around 7.2 ounces volume) of Calcium Chloride Dihydrate. I suspect that you have the dihydrate form of Calcium Chloride.

I just looked on the label again, and it doesn't say what it is. However, it does give a dosage chart. It says to raise CH 100 ppm in a 5000 gal pool you add 6.25 lbs.

So: 6.25 x 28 = 175 oz / 5000 = 0.035 x 320 = 11.2 oz (weight) / 1.4 = 8 oz (volume).

That explains it. I wish I would have read the label more closely before, because I wasted a lot of Calcium reagent/buffer rechecking it multiple times.

I may up it to 250 though. That will give me well balanced water with TA at 60, pH at 7.8 and Borates at 50.

[LauraG]

Richard, the pH was still 7.0 so, I added just one teaspoon pH up and aerated for an hour, now it's 7.8. I am developing a yellowy brownish stain around the water line, and I can't scrub it off. This was before the 7.8 pH, although I have no idea if this is a factor.

Is that a stain, or is it more of a film? Is it slippery to the touch? Try putting a little Baking Soda on a wet rag and wipe it off. Careful with the BS, because it will raise your TA if you use too much.

It is a stain for sure, and not slippery to the touch. I will carefully wipe with the BS. Thanks.

I've just completed my tests.

FC 5

pH 7.2

TA 50

CYA 30

CH 200

I have not cleaned the 'ring' with the baking soda yet. I will do that tonight. Then I will areate again.

Are these reading ok? They are all lower than Nitro's.

[Maxemily]

I've just completed my tests.

FC 5

pH 7.2

TA 50

CYA 30

CH 200

I have not cleaned the 'ring' with the baking soda yet. I will do that tonight. Then I will areate again.

Are these reading ok? They are all lower than Nitro's.

Not really. Plug the numbers in here and you will see the problem. By playing around you can also see what works to correct the balance.

[Nitro]

I've just completed my tests.

FC 5

pH 7.2

TA 50

CYA 30

CH 200

I have not cleaned the 'ring' with the baking soda yet. I will do that tonight. Then I will areate again.

Are these reading ok? They are all lower than Nitro's.

Have you been aerating? That pH is still a little low. You need to get it up to 7.6-7.8. If you're having trouble getting your pH up, you can raise your TA to 60 with Baking Soda. But remember, you'll be using Baking Soda to clean that stain. Don't add any BS until your done cleaning, because you may not need it afterward.

Have you been using MPS? If so just remember that's acidic and will lower your TA/pH.

Also, do you have Borates in your tub? If so that will require you to raise something (TA or CH) even more.

A balanced hot tub is CH 200, TA 60 and pH 7.8. If any of those numbers are lower, you're acidic, and need to raise either TA or CH. If you can get that pH up to 7.8, you'll still be a little acidic, but not bad. If it worries you, you can raise your TA to 60 or CH to 250 and be perfect. However, if you raise your TA you may have pH Drift issues, and if you raise your CH you can't take it back out without refilling.

I would just continue to aerate, clean the stain and test again.

[LauraG]

I've just completed my tests.

FC 5

pH 7.2

TA 50

CYA 30

CH 200

I have not cleaned the 'ring' with the baking soda yet. I will do that tonight. Then I will areate again.

Are these reading ok? They are all lower than Nitro's.

Have you been aerating? That pH is still a little low. You need to get it up to 7.6-7.8. If you're having trouble getting your pH up, you can raise your TA to 60 with Baking Soda. But remember, you'll be using Baking Soda to clean that stain. Don't add any BS until your done cleaning, because you may not need it afterward.

Have you been using MPS? If so just remember that's acidic and will lower your TA/pH.

Also, do you have Borates in your tub? If so that will require you to raise something (TA or CH) even more.

A balanced hot tub is CH 200, TA 60 and pH 7.8. If any of those numbers are lower, you're acidic, and need to raise either TA or CH. If you can get that pH up to 7.8, you'll still be a little acidic, but not bad. If it worries you, you can raise your TA to 60 or CH to 250 and be perfect. However, if you raise your TA you may have pH Drift issues, and if you raise your CH you can't take it back out without refilling.

I would just continue to aerate, clean the stain and test again.

Thanks Nitro..... I have been aerating. Actually, the pH was up to 7.8 on Saturday after adding pH up and lot's of aerating. So, I was surprised to see it drop down by today.

I have not used any MPS so far.

As far as the Borates, I have put in Omni Presense Plus (which is supposed to be the same as SpaGuard-Canadian) Hopefully this is mostly Boric Acid, but there are no ingredients on the container! I am going to try to find out what is in it.

I will do nothing until I use the Baking Soda tonight.

I'm going away for the weekend and want to make sure things are ok before I go. My daughter is going to check it (I'm sure she'll be using it as well!! LOL)

[chem geek]

Also, do you have Borates in your tub? If so that will require you to raise something (TA or CH) even more.

The Omni Presence Plus was presumably Borates. One way to test for Borates is with LaMotte InstaTest Borate test strip. It's one of the few test strips that reliably does a good job (the other being the AquaChek White Salt test strip though I've used the Taylor K-1766 with a 25 ml sample size for 80 ppm per drop resolution and it works reasonably well -- however, the endpoint is more clear with the recommended 10 ml sample size for 200 ppm per drop resolution).

Since the Borates have been added, using some pH Up would be appropriate. About 5 teaspoons in 380 gallons would raise the pH to 7.6, assuming there is 50 ppm Borates in the water., but that would raise the TA to 68 ppm (about 70 ppm). I'd suggest adding 2 teaspoons and retesting the pH after about a half hour. Since the pH doesn't seem to be rising much, having the higher TA is probably OK. Another alternative would be to add 11 teaspoons of 20 Mule Team Borax to raise the pH as this would only have the TA rise to about 60 ppm (and would raise the Borates by about 4 ppm). Unfortunately, I don't think Laura was able to find Borax (sodium tetraborate decahydrate) in the grocery store.

I was expecting the pH to rise more from aeration, but since it isn't, the above corrections are appropriate. Looks like Laura's going to have reasonably stable pH after all, even using the bleach.

Richard

[Nitro]

I was expecting the pH to rise more from aeration, but since it isn't, the above corrections are appropriate. Looks like Laura's going to have reasonably stable pH after all, even using the bleach.

That seems to be consistant with my experience. TA of 60 and Borates of 50 kept pH drift in line for me. So that would suggest a TA of 50 may be a little too low.

Also, I found that my pH would drop from 7.8 to 7.6 if I didn't use the tub for a day or two. Maybe that's what Laura is experiencing.

[Nitro]

Thanks Nitro..... I have been aerating. Actually, the pH was up to 7.8 on Saturday after adding pH up and lot's of aerating. So, I was surprised to see it drop down by today.

I have not used any MPS so far.

As far as the Borates, I have put in Omni Presense Plus (which is supposed to be the same as SpaGuard-Canadian) Hopefully this is mostly Boric Acid, but there are no ingredients on the container! I am going to try to find out what is in it.

I will do nothing until I use the Baking Soda tonight.

I'm going away for the weekend and want to make sure things are ok before I go. My daughter is going to check it (I'm sure she'll be using it as well!! LOL)

I think you are pretty close to being tuned. What you don't want to do is keep overshooting the ideal TA. Anything you do to change TA now should be in very small increments. Your ideal TA could be 55.

Just cleaning the water line might add enough Baking Soda to bring your TA up to ideal. BTW, ~1 tbs of Baking Soda will raise your TA from 50 to 60. Keep that in mind while your cleaning, so you don't add too much to the water. After you clean it recheck your TA/pH.

[LauraG]

Thanks Nitro..... I have been aerating. Actually, the pH was up to 7.8 on Saturday after adding pH up and lot's of aerating. So, I was surprised to see it drop down by today.

I have not used any MPS so far.

As far as the Borates, I have put in Omni Presense Plus (which is supposed to be the same as SpaGuard-Canadian) Hopefully this is mostly Boric Acid, but there are no ingredients on the container! I am going to try to find out what is in it.

I will do nothing until I use the Baking Soda tonight.

I'm going away for the weekend and want to make sure things are ok before I go. My daughter is going to check it (I'm sure she'll be using it as well!! LOL)

I think you are pretty close to being tuned. What you don't want to do is keep overshooting the ideal TA. Anything you do to change TA now should be in very small increments. Your ideal TA could be 55.

Just cleaning the water line might add enough Baking Soda to bring your TA up to ideal. BTW, ~1 tbs of Baking Soda will raise your TA from 50 to 60. Keep that in mind while your cleaning, so you don't add too much to the water. After you clean it recheck your TA/pH.

Hi chem geek and nitro

I am going to use the baking soda to clean, plus add 2 teaspoons pH up along with aeration now.

I will try again to get 20 Mule Team Borax, as I didn't try too hard because I was hoping the Omin Presence Plus would do the trick. I will re-check the pH after 1/2 an hour.

As my TA is 60, I will be very careful with the BS.

[LauraG]

Thanks Nitro..... I have been aerating. Actually, the pH was up to 7.8 on Saturday after adding pH up and lot's of aerating. So, I was surprised to see it drop down by today.

I have not used any MPS so far.

As far as the Borates, I have put in Omni Presense Plus (which is supposed to be the same as SpaGuard-Canadian) Hopefully this is mostly Boric Acid, but there are no ingredients on the container! I am going to try to find out what is in it.

I will do nothing until I use the Baking Soda tonight.

I'm going away for the weekend and want to make sure things are ok before I go. My daughter is going to check it (I'm sure she'll be using it as well!! LOL)

I think you are pretty close to being tuned. What you don't want to do is keep overshooting the ideal TA. Anything you do to change TA now should be in very small increments. Your ideal TA could be 55.

Just cleaning the water line might add enough Baking Soda to bring your TA up to ideal. BTW, ~1 tbs of Baking Soda will raise your TA from 50 to 60. Keep that in mind while your cleaning, so you don't add too much to the water. After you clean it recheck your TA/pH.

Hi chem geek and nitro

I am going to use the baking soda to clean, plus add 2 teaspoons pH up along with aeration now.

I will try again to get 20 Mule Team Borax, as I didn't try too hard because I was hoping the Omin Presence Plus would do the trick. I will re-check the pH after 1/2 an hour.

As my TA is 60, I will be very careful with the BS.

Well, I tried to be very careful, but.....the TA is now 100. oh oh

pH was 7.8 This is good news

I put a bit of BS in a bowl and just dabbed some on the end of a sponge to scrub. My husband helped me, and I believe it was HIM who over did it. All in all, there was approx. 1 to 1 1/2 teaspoons in the bowl...

After the soak, I added 4 oz. of Purox, as the FC was almost nil. Now it is 7.0

Surely by now, I must be driving you both crazy!!!

[Nitro]

Well, I tried to be very careful, but.....the TA is now 100. oh oh

pH was 7.8 This is good news

I put a bit of BS in a bowl and just dabbed some on the end of a sponge to scrub. My husband helped me, and I believe it was HIM who over did it. All in all, there was approx. 1 to 1 1/2 teaspoons in the bowl...

After the soak, I added 4 oz. of Purox, as the FC was almost nil. Now it is 7.0

Surely by now, I must be driving you both crazy!!!

Well, did the stain come out?

[chem geek]

Well, I tried to be very careful, but.....the TA is now 100. oh oh

pH was 7.8 This is good news

I put a bit of BS in a bowl and just dabbed some on the end of a sponge to scrub. My husband helped me, and I believe it was HIM who over did it. All in all, there was approx. 1 to 1 1/2 teaspoons in the bowl...

After the soak, I added 4 oz. of Purox, as the FC was almost nil. Now it is 7.0

Surely by now, I must be driving you both crazy!!!

Well, that's very weird. Even 1-1/2 teaspoons of baking soda plus 2 teaspoons of pH Up and 4 ounces of Purox would go from a pH of 7.2 and TA of 50 to a pH of 7.6 and TA of 67 (so around 70) assuming you've got around 50 ppm Borates now. The soak with jets on would aerate the water so the higher pH is understandable, but a TA of 100 is not -- unless more baking soda and/or pH Up was added than you thought. If it was 1-1/2 tablespoons of baking soda and 2 tablespoons of pH Up, then that would get you to a pH of 7.8 and TA of 88 (so around 90 -- 100 if you started at 60), but you're sure you are using teaspoons, right? I'm also assuming, based on a PM from you, that your spa is 380 U.S. gallons (not U.K. Imperial) even though you thought it might be U.K. Imperial in a post of yours.

As was noted by some other posters, in the future you should probably add less than you think and remeasure at least 15 minutes after mixing to see where you are at.

At this point, watch the pH and add small amounts of dry acid to lower the pH to not lower than 7.5, say after your next soak. Don't add more than one tablespoon (3 teaspoons) of dry acid at a time without remeasuring. It's more about seeing a pattern and you should measure the pH at the same point in your procedure, such as soon after your soak and before you add more chlorine. I wonder if you're bringing something in with your suits when soaking, though I wouldn't expect baking soda in them (detergents shouldn't raise the TA).

Richard

[Nitro]

Yeah, that does seem like a big jump in TA from 60 to 100 for such a little amount of BS and pH Up.

Laura, are you sure you're measuring TA correctly? You may want to take a 2nd reading, just to make sure.

[keith55]

Richard,

I enjoyed the explanation on aeration and pH. I've followed the tread on Water Quality and its been very helpful. Our municipal water supply come from an usually aquifer.

pH 8.3

TA 230

CH 30

I've been trying to get my spa in balance, and have had problems with pH drift. Over several weeks I've added 3/4 cup of muriatic acid and 10oz Cacl2. The pH has stabilized at 7.7, but the TA is low and my CSI is negative.

Spa 375 gallons

pH 7.7

TA 30

CH 140

Temp 100

If I add baking soda, run the problem with pH. Any suggestions. Thanks, KEith

[chem geek]

If I add baking soda, run the problem with pH. Any suggestions. Thanks, KEith

You can add baking soda to get to a TA of around 60 ppm -- I wouldn't go lower than 50 ppm in any event. If your pH tends to drift upwards, then you can consider using Borates to stabilize the pH. The easiest way to add the Borates for a spa is to use Boric Acid since it's closer to pH neutral or use a pH balanced product such as Proteam Supreme Plus or SpaGuard/BioGuard Spa Optimizer Plus. The Borates will not actually change the amount of equivalent "per day" acid you need to add, but it will slow down the rate of pH rise so that you don't need to add acid as often.

Richard

[LauraG]

Yeah, that does seem like a big jump in TA from 60 to 100 for such a little amount of BS and pH Up.

Laura, are you sure you're measuring TA correctly? You may want to take a 2nd reading, just to make sure.

Well, I have re-checked again (twice) very carefully.

FC 5

TA 75

pH 7.8

CH 175

What do you think? Should I do anything?

Also I should mention that I looked at the bowl my husband was using and he didn't use as much as I had first thought.

I was using a teaspoon, not a tablespoon.

[LauraG]

Well, I tried to be very careful, but.....the TA is now 100. oh oh

pH was 7.8 This is good news

I put a bit of BS in a bowl and just dabbed some on the end of a sponge to scrub. My husband helped me, and I believe it was HIM who over did it. All in all, there was approx. 1 to 1 1/2 teaspoons in the bowl...

After the soak, I added 4 oz. of Purox, as the FC was almost nil. Now it is 7.0

Surely by now, I must be driving you both crazy!!!

Well, that's very weird. Even 1-1/2 teaspoons of baking soda plus 2 teaspoons of pH Up and 4 ounces of Purox would go from a pH of 7.2 and TA of 50 to a pH of 7.6 and TA of 67 (so around 70) assuming you've got around 50 ppm Borates now. The soak with jets on would aerate the water so the higher pH is understandable, but a TA of 100 is not -- unless more baking soda and/or pH Up was added than you thought. If it was 1-1/2 tablespoons of baking soda and 2 tablespoons of pH Up, then that would get you to a pH of 7.8 and TA of 88 (so around 90 -- 100 if you started at 60), but you're sure you are using teaspoons, right? I'm also assuming, based on a PM from you, that your spa is 380 U.S. gallons (not U.K. Imperial) even though you thought it might be U.K. Imperial in a post of yours.

As was noted by some other posters, in the future you should probably add less than you think and remeasure at least 15 minutes after mixing to see where you are at.

At this point, watch the pH and add small amounts of dry acid to lower the pH to not lower than 7.5, say after your next soak. Don't add more than one tablespoon (3 teaspoons) of dry acid at a time without remeasuring. It's more about seeing a pattern and you should measure the pH at the same point in your procedure, such as soon after your soak and before you add more chlorine. I wonder if you're bringing something in with your suits when soaking, though I wouldn't expect baking soda in them (detergents shouldn't raise the TA).

Richard

Well, the tub is 1430 litres, and it is pretty close to 380 U.S. gallons right? Or am I wrong?

A far as I know, no one's suit is carrying baking soda....but I will ask them all!!! LOL

Seriously though, I have a 'proper' measuring teaspoon now, not one from the kitchen drawer!!!