Yes, basically your significantly cutting down any effect of carbon dioxide outgassing and for physical disturbance of the plaster. So what's left is the plaster doing its thing on its own We'll see what happens.
Crazy ph
- Thread starter christianday
- Start date
Today's numbers, still no jets and now the TA is up to 70 from 45 and the pH has gone up from 6.8 to way over 8.2:
| Date | 7/7/15 |
| Time | 2:56 PM |
| pH: | >8.2 |
| FC: | - |
| CC: | - |
| TC: | - |
| TA: | 70 |
| CH: | - |
| CYA: | - |
This is a very bizarre problem. Yesterday over 7.5 hours the pH rose from 7.5 to 7.8 with no apparent change in TA, but today over around 14 hours it jumped from 7.8 (not 6.8, that was a typo) to over 8.2 with the TA rising from 60 ppm to 70 ppm.
So given the amount of pH rise, I would have expected to see the TA rise even more. If calcium hydroxide were getting released from plaster, then one can go from 7.5 to 8.2 with 24 ppm TA increase so the first day with 8 ppm over 7.5 hours would go from 7.5 to 7.8 while the second day over 14 hours it would be twice as much or 16 ppm. So it doesn't seem to be slowing down, but the pH does seem to be rising more than the TA.
So the good news from this is that some of the calcium hydroxide may instead be getting converted to calcium carbonate and that causes the pH to rise with no change in TA. So if that means that the plaster is "healing" so that it's calcium hydroxide that is solidifying, then that is a good thing. If you want to encourage that, then only add acid to get down to a pH of 7.8 and not lower.
So here's what I get with my spreadsheet with some assumptions (and your water parameters):
Over around 7 hours
5 ppm CaCO3 equivalent of calcium hydroxide release into the pool water PLUS
10 ppm CaCO3 of calcium hydroxide converting to calcium carbonate
has pH rise from 7.5 to 7.85 and TA rise from 60 to 64.8 and CH rise by 5 ppm
THEN Over around 14 hours
10 ppm CaCO3 equivalent of calcium hydroxide release into the pool water PLUS
20 ppm CaCO3 of calcium hydroxide converting to calcium carbonate
has pH rise from 7.85 to 8.27 and TA rise from 64.8 to 74.2 and CH rise by 15 ppm
So if this is what is happening now, then as the TA rises and you keep the pH on the high side one should see more of the calcium hydroxide become calcium carbonate and hopefully seal off the plaster to slow down this process.
It's very clear that with the jets off and low TA that the pH rise is most certainly not coming from carbon dioxide outgassing, but also the good news is that it isn't all from calcium hydroxide either but that some calcium hydroxide is converting to calcium carbonate which is a good thing. The other good news is that it doesn't look like you've got much if any calcium carbonate dissolving so plaster that is solid is remaining so. What appears to have happened is that the large acid additions may have pooled or gotten the pH too low breaking through the plaster calcium carbonate surface and exposing the calcium hydroxide underneath and now it is in the process of essentially resealing.
So given the amount of pH rise, I would have expected to see the TA rise even more. If calcium hydroxide were getting released from plaster, then one can go from 7.5 to 8.2 with 24 ppm TA increase so the first day with 8 ppm over 7.5 hours would go from 7.5 to 7.8 while the second day over 14 hours it would be twice as much or 16 ppm. So it doesn't seem to be slowing down, but the pH does seem to be rising more than the TA.
So the good news from this is that some of the calcium hydroxide may instead be getting converted to calcium carbonate and that causes the pH to rise with no change in TA. So if that means that the plaster is "healing" so that it's calcium hydroxide that is solidifying, then that is a good thing. If you want to encourage that, then only add acid to get down to a pH of 7.8 and not lower.
So here's what I get with my spreadsheet with some assumptions (and your water parameters):
Over around 7 hours
5 ppm CaCO3 equivalent of calcium hydroxide release into the pool water PLUS
10 ppm CaCO3 of calcium hydroxide converting to calcium carbonate
has pH rise from 7.5 to 7.85 and TA rise from 60 to 64.8 and CH rise by 5 ppm
THEN Over around 14 hours
10 ppm CaCO3 equivalent of calcium hydroxide release into the pool water PLUS
20 ppm CaCO3 of calcium hydroxide converting to calcium carbonate
has pH rise from 7.85 to 8.27 and TA rise from 64.8 to 74.2 and CH rise by 15 ppm
So if this is what is happening now, then as the TA rises and you keep the pH on the high side one should see more of the calcium hydroxide become calcium carbonate and hopefully seal off the plaster to slow down this process.
It's very clear that with the jets off and low TA that the pH rise is most certainly not coming from carbon dioxide outgassing, but also the good news is that it isn't all from calcium hydroxide either but that some calcium hydroxide is converting to calcium carbonate which is a good thing. The other good news is that it doesn't look like you've got much if any calcium carbonate dissolving so plaster that is solid is remaining so. What appears to have happened is that the large acid additions may have pooled or gotten the pH too low breaking through the plaster calcium carbonate surface and exposing the calcium hydroxide underneath and now it is in the process of essentially resealing.
I'm going to re-test the calcium in a few. The pool builder just went to Leslie's to get the water analyzed. We don't plan to necessarily buy all their chemical suggestions but just to get some insight.
I am convinced it's the plaster. I called the local pool maintenance company that I found online and they don't do SWG pools. They sent me to a local who does maintain SWG pools and he said the new plaster usually makes for high pH but said that it should be almost done. HOWEVER, both he and the pool builder said I should have been brushing the plaster weekly and we haven't been. I thought it was just the twice a day for a couple weeks when you first fill the water. However, this SWG pool maintenance guy had no idea that aeration can raise pH at all and had never heard of CO2 outgassing. That makes me a little nervous. I think I'd rather get an acid dispenser than have this guy maintaining my pool.
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I still plan to replace the water but I want to wait until the plaster is more fully cured. Then, with the right amount of calcium added to the pool, that problem should be over and I don't have to deal with the effects of the residuals.
I am convinced it's the plaster. I called the local pool maintenance company that I found online and they don't do SWG pools. They sent me to a local who does maintain SWG pools and he said the new plaster usually makes for high pH but said that it should be almost done. HOWEVER, both he and the pool builder said I should have been brushing the plaster weekly and we haven't been. I thought it was just the twice a day for a couple weeks when you first fill the water. However, this SWG pool maintenance guy had no idea that aeration can raise pH at all and had never heard of CO2 outgassing. That makes me a little nervous. I think I'd rather get an acid dispenser than have this guy maintaining my pool.
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I still plan to replace the water but I want to wait until the plaster is more fully cured. Then, with the right amount of calcium added to the pool, that problem should be over and I don't have to deal with the effects of the residuals.
I might have missed it, but why the increase in pump time? And, is it a bit troublesome that you reported a CC of 1, twice?
So that you know the processes of what happens with plaster, it's a two stage process. The first stage is plaster curing or hydration is the following:
Tricalcium Silicate + Water ---> Calcium Silicate Hydrate + Calcium Hydroxide + heat
Soft Uncured Plaster + Water ---> Hard Cured Plaster + Soft Slack Lime + heat
The above happens pretty quickly where the new cement is hydrated in the hours to days after a plaster job is completed and continues much more slowly over weeks to months. The second stage (that starts in parallel right after the first is started) that I call plaster hardening is the following:
Calcium Hydroxide + Bicarbonate Ion ---> Calcium Carbonate + Water + Hydroxide Ion
Soft Slack Lime + "TA" ---> Hard Limestone + Water + "High pH"
where the soft water soluble calcium hydroxide by-product of the first stage gets hardened by the TA in the water to form hard calcium carbonate. Depending on the type of plaster start-up procedure, this calcium carbonate can form mostly in the plaster (with a bicarbonate start-up) or a lot may slough off (or be brushed off) and form in the pool as plaster dust (with an acid start-up). It's easy to distinguish between these because in a bicarbonate start-up there is very little plaster dust and the Calcium Hardness (CH) level doesn't rise very much while with an acid start-up there is a lot of plaster dust and the CH rises a lot. In all plater startups, the pH rises and acid must be added to keep the pH in check.
Technically, the very soft cement becomes hard during curing but it is then a mixture of hard calcium silicate hydrate with soft calcium hydroxide so when I say that the second stage is plaster hardening I mean in the sense of "further hardening" of a component of plaster in between the already cured component. This plaster hardening that forms calcium carbonate does so on a thin surface of the plaster. Deeper in the plaster there remains thick but not hard calcium hydroxide. In some sense it's like a time bomb waiting to go off if the surface layer of the plaster breaks open and if the water is saturated with calcium carbonate then you can get Calcium Nodules in Pools.
Tricalcium Silicate + Water ---> Calcium Silicate Hydrate + Calcium Hydroxide + heat
Soft Uncured Plaster + Water ---> Hard Cured Plaster + Soft Slack Lime + heat
The above happens pretty quickly where the new cement is hydrated in the hours to days after a plaster job is completed and continues much more slowly over weeks to months. The second stage (that starts in parallel right after the first is started) that I call plaster hardening is the following:
Calcium Hydroxide + Bicarbonate Ion ---> Calcium Carbonate + Water + Hydroxide Ion
Soft Slack Lime + "TA" ---> Hard Limestone + Water + "High pH"
where the soft water soluble calcium hydroxide by-product of the first stage gets hardened by the TA in the water to form hard calcium carbonate. Depending on the type of plaster start-up procedure, this calcium carbonate can form mostly in the plaster (with a bicarbonate start-up) or a lot may slough off (or be brushed off) and form in the pool as plaster dust (with an acid start-up). It's easy to distinguish between these because in a bicarbonate start-up there is very little plaster dust and the Calcium Hardness (CH) level doesn't rise very much while with an acid start-up there is a lot of plaster dust and the CH rises a lot. In all plater startups, the pH rises and acid must be added to keep the pH in check.
Technically, the very soft cement becomes hard during curing but it is then a mixture of hard calcium silicate hydrate with soft calcium hydroxide so when I say that the second stage is plaster hardening I mean in the sense of "further hardening" of a component of plaster in between the already cured component. This plaster hardening that forms calcium carbonate does so on a thin surface of the plaster. Deeper in the plaster there remains thick but not hard calcium hydroxide. In some sense it's like a time bomb waiting to go off if the surface layer of the plaster breaks open and if the water is saturated with calcium carbonate then you can get Calcium Nodules in Pools.
PAGirl: since the CC is almost always at zero and very occasionally .5, and this 1 was a "just barely" over .5 sorta thing, I'm guessing the organics setting that off are the never-ending supply of bugs and occasional litter from the landscaping around the pool. I could be wrong but the water is always pretty crystal clear.
chem geek:I'm not totally understanding what you said but I'm guessing the basic gist of it is that I need to add more acid these days because the plaster is new. I wonder if it doesn't help that the water is usually 85 to 90 degrees fahrenheit.
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Oh, and PAGirl: the increase in pump time to 20 hours is because of the never-ending supply of tiny bugs. LOL
chem geek:I'm not totally understanding what you said but I'm guessing the basic gist of it is that I need to add more acid these days because the plaster is new. I wonder if it doesn't help that the water is usually 85 to 90 degrees fahrenheit.
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Oh, and PAGirl: the increase in pump time to 20 hours is because of the never-ending supply of tiny bugs. LOL
I was just telling you the normal process and yes plaster does tend to keep rising in pH for a while, but your situation is far from normal. Something got broken in the process so your pool is now acting more like a newer plaster pool with a substantial pH (and some TA) rise. We'll hopefully get that fixed by letting the water get more saturated with calcium carbonate by letting the TA climb and not lowering the pH as much. At some point you might even need to add baking soda (sodium bicarbonate), but we aren't there yet.
You can brush the pool as your plaster people recommend. That will remove any loose substances at the surface and allow the bicarbonate in the water to form harder calcium carbonate into the plaster itself. The pool may get temporarily cloudy when you brush.
I just added some laymen's terms that might be easier to understand where the first stage goes from soft uncured plaster combining with water to form hard cured plaster plus a soft component (called soft "slake lime"). The second stage goes from that soft slake lime combining with TA in the water to form hard limestone. Hopefully that makes some more sense.
You can brush the pool as your plaster people recommend. That will remove any loose substances at the surface and allow the bicarbonate in the water to form harder calcium carbonate into the plaster itself. The pool may get temporarily cloudy when you brush.
I just added some laymen's terms that might be easier to understand where the first stage goes from soft uncured plaster combining with water to form hard cured plaster plus a soft component (called soft "slake lime"). The second stage goes from that soft slake lime combining with TA in the water to form hard limestone. Hopefully that makes some more sense.
It makes more sense, yes. The pH went up more but the TA is holding at 70. I doubt it will stay there long though and I'm not adding any acid till the pool builder comes back with the recommendations from Leslie's. I don't imagine they'll be that usable but you never know.
OK. So long as you don't have metals in the water then you shouldn't get metal staining. That's the biggest risk from the high pH. I don't think you are risking scaling yet, but at some point that will become a risk as well so hopefully the pool builder will come back soon and tell you can add acid, but probably only to keep the pH below 8.2 and not to drop the pH below 7.8. They should also say to let the TA rise some.
So yesterday and today was three quarts MA and the pH never went below 8.2. So I just dumped another gallon and a half. Tomorrow, I'm draining the pool. If the plaster is the problem, I have no idea what to do. What if I left the pool drained for a few months. Will the plaster cure better then?
No, the plaster won't change without water. The calcium hydroxide will just sit there and when you next add water it will react again unless you do something different with the water. Let me see if I can get onBalance here to see if maybe trying to do a Bicarbonate "recovery" (since it's not a start-up) might help.
BOY HOWDY DON"T DO IT!! First off, the water table in New Orleans is so high you'll end up with a pool flying out of the ground ("Floated") Does your pool have hydrostatic valves built in the bottom?
An empty plaster pool can be damaged by drying out. Folks sometimes set up sprinklers or ways to spray down the pool when doing repairs.....not sure if that's feasible for "months"??
An empty plaster pool can be damaged by drying out. Folks sometimes set up sprinklers or ways to spray down the pool when doing repairs.....not sure if that's feasible for "months"??
Oh, well then I definitely won't leave it empty.
Still, draining and refilling will be better without the borates. I am not sure why the borates do not slow the rise in pH the way they are supposed to. If anything, the pH rises much faster since I added borates. However, since it does slow down the fall of it, I end up having to add four times as much. Tonight, I went overboard though and had to add pH Up just to bring it back to a safe range. But still, even the amount I would have needed was still way more because of the borates. At least if I drain and refill, the pH spike won't be as high and I'll be able to drop it with a LOT less MA. Getting the sense and dispense system (and just using the pH, probably not the chlorine part unless that proves to work well) so the acid can be gradually added throughout the week. My chlorine is always pretty good so it's just the pH I'm trying to fix.
Still, draining and refilling will be better without the borates. I am not sure why the borates do not slow the rise in pH the way they are supposed to. If anything, the pH rises much faster since I added borates. However, since it does slow down the fall of it, I end up having to add four times as much. Tonight, I went overboard though and had to add pH Up just to bring it back to a safe range. But still, even the amount I would have needed was still way more because of the borates. At least if I drain and refill, the pH spike won't be as high and I'll be able to drop it with a LOT less MA. Getting the sense and dispense system (and just using the pH, probably not the chlorine part unless that proves to work well) so the acid can be gradually added throughout the week. My chlorine is always pretty good so it's just the pH I'm trying to fix.
ewkearns
0
If you have a hydrostatic well (and in NOLA, I can't image not having at least one) you'd better be pumping like crazy. If you can't bury people below ground, because caskets float.... image that your pool is nothing more than a ferrocement boat and once no longer filled with water (sunk) it WILL float.... right out of the ground....
I've been following this thread with interest -- this certainly an unusual situation, and must be extremely frustrating for you.
It seems to me, though, that you need to continue to work on finding the underlying reason for the continual abnormal rises in pH and TA, and resolve that underlying reason (maybe with that recovery process that chem geek mentioned a few posts ago). Adding an automated acid dispenser seems convenient, certainly, but it's also a way of hiding the symptoms rather than getting at the root cause.
Has the possibility of problems at the SWG end (I think it was suggested that short runs and undissolved chlorine gas could, hypothetically, be contributing to the weird pool chemistry) been definitely dismissed? Might it be worth an experiment of switching the SWG off, and manually dosing with bleach for a few days to see if the pool's behavior changes? I guess that's a question for chem geek, and/or the other experts guiding you here.
Maybe it helps to think of all this as a short term experiment (relatively speaking) to figure out what is going on with your pool; not that you will be facing this much daily drudgery and frustration for years to come in owning this pool.
Where is your pool builder in all this? He seems surprisingly absent from the discussion, given how young this pool is...
It seems to me, though, that you need to continue to work on finding the underlying reason for the continual abnormal rises in pH and TA, and resolve that underlying reason (maybe with that recovery process that chem geek mentioned a few posts ago). Adding an automated acid dispenser seems convenient, certainly, but it's also a way of hiding the symptoms rather than getting at the root cause.
Has the possibility of problems at the SWG end (I think it was suggested that short runs and undissolved chlorine gas could, hypothetically, be contributing to the weird pool chemistry) been definitely dismissed? Might it be worth an experiment of switching the SWG off, and manually dosing with bleach for a few days to see if the pool's behavior changes? I guess that's a question for chem geek, and/or the other experts guiding you here.
Maybe it helps to think of all this as a short term experiment (relatively speaking) to figure out what is going on with your pool; not that you will be facing this much daily drudgery and frustration for years to come in owning this pool.
Where is your pool builder in all this? He seems surprisingly absent from the discussion, given how young this pool is...
I calculated the worst-case of what the SWCG could be doing and given the % ontime and model, it can't be the main source of the problem. The pH rise still shows up even with the SWCG turned off (such as overnight). Certainly one can try turning off the SWCG and manually chlorinating just to eliminate that as a possibility, but I'm pretty sure the source is the plaster. Pretty much everything is now explained except for why the rate of rise got worse with the borates addition. The only thing I can think of for that is that the borates had less of a pH rise at the plaster surface so the plaster didn't reseal as much (especially if the TA was too low) so released more calcium hydroxide into the water instead of forming calcium carbonate in the plaster itself. That is, the borates work well when the plaster is in good shape (i.e. after curing and well sealed so not releasing calcium hydroxide), but may inhibit sealing if a problem already exists unless one raises the TA level a with a bicarbonate start-up (i.e. the water needs to be saturated with calcium carbonate).
I think the main sequence of events was the following:
If an acid injection system is used to automate pH control, then the TA will also need to be maintained because the CO2 outgassing from the swim jets only raises the pH with no change in TA. So it might be better to get a CO2 injection system for pH control. Then only a small amount of acid would be needed to keep the TA in check. This is very much what commercial/public pools do to minimize their costs, but I don't know if there are residential systems that do this. Technically, acid + bicarbonate is identical to injecting carbon dioxide (except that acid + bicarbonate also increases sodium chloride salt).
I think the main sequence of events was the following:
- New plaster curing had pH rise as well as use of swim jets that had pH rise from CO2 outgassing.
- Acid was added to control the pH, but it was added quickly and the TA was not always monitored so the plaster got degraded due to sometimes lower TA and initially lower CH and mostly direct exposure to concentrated acid that was not well distributed/mixed in the pool.
- Plaster degradation resulted in calcium carbonate getting dissolved from the plaster which has the CH, pH and TA all rise.
- The removal of this calcium carbonate from the surface of the plaster exposed calcium hydroxide underneath which when released into the pool raises the CH, pH, and TA where the pH and TA rise even more than with calcium carbonate dissolving.
- More acid was added which perpetuated this cycle. Then Borates were added that buffered the pH including locally at the plaster surface making it even more difficult for the plaster to reseal with calcium carbonate (due to the lower TA from acid addition).
- More recently, the rate of TA rise has slowed so the calcium hydroxide in the plaster is getting converted to calcium carbonate in place and that causes the pH to rise with no change in CH or TA. This is a good thing in that the plaster is trying to seal.
- However, the acid addition to get the pH down always lowers the TA but whereas before the TA rise from the plaster hid that fact and even had the net TA rise, now the net effect on TA is a drop from the acid (because the plaster is just raising pH and not TA or CH anymore) so the TA got too low.
- The low TA repeats the cycle of degrading the plaster especially if the pH gets low as well.
If an acid injection system is used to automate pH control, then the TA will also need to be maintained because the CO2 outgassing from the swim jets only raises the pH with no change in TA. So it might be better to get a CO2 injection system for pH control. Then only a small amount of acid would be needed to keep the TA in check. This is very much what commercial/public pools do to minimize their costs, but I don't know if there are residential systems that do this. Technically, acid + bicarbonate is identical to injecting carbon dioxide (except that acid + bicarbonate also increases sodium chloride salt).
Sorry I am late and don't know the entire history, but I have a few questions.
I noticed that the TA of your tap water is 140 ppm. What is the CH of your tap water?
Do you remember the temperature the day of plastering?
How long after the pool was finished was salt added to your pool?
Was a special type of chemical start-up process (such as an Acid start) used at the beginning? Please describe.
I noticed that the TA of your tap water is 140 ppm. What is the CH of your tap water?
Do you remember the temperature the day of plastering?
How long after the pool was finished was salt added to your pool?
Was a special type of chemical start-up process (such as an Acid start) used at the beginning? Please describe.
ewkearns: the pool was empty for at least a two weeks before being filled so I wouldn't leave it empty long.
singingpond: Yeah. The pool builder is a bit hard to find right now. He doesn't understand the chemistry AT ALL and his guy that does is baffled by this. I've called several pool professionals and none of them understand. One doesn't do SWG at all and one that did had no idea that aeration raises pH so I wasn't trusting these people to help. I'm reticent to start manually chlorinating. I wonder if it's the filter running more often because of the termite swarms and bugs that occasionally end up in there, though the SWG is not running any longer because I drop the percentage.
chem geek: I actually never added acid when I didn't check the pH and TA after. The lowest I ever got it before a couple days ago was 50, when I added the borates, the pH was already crazy before that and the lowest I'd gotten it before that was 60, which isn't that low for SWG. A couple nights ago I got it to 20 but I immediately raised it up with sodium carbonate. Originally the Hayward Sense and Dispense used CO2 but apparently they use an acid tank now. I'm not sure why but I'd prefer the CO2 if it's possible to get though they may not support it. I want Hayward equipment because it's all controlled by the OmniLogic which I love.
onBalance: Thank you for weighing in. I can answer some of that:
1. The CH of the tap water tested at 175. The TA, as you mentioned, is 140, and the pH is higher than 8.2, though probably too much higher.
2. I don't know what the temp was like the day of plaster but it was probably around 70 to 80.
3. The salt was added within 24 hours of filling the pool.
4. I don't know but there was an unopened bottle of muriatic acid left behind so I'm guessing they used some beforehand. I will find out when I can get the pool builder to call me back. I'm having some difficulties there. New Orleans is an interesting place, to put it kindly.
singingpond: Yeah. The pool builder is a bit hard to find right now. He doesn't understand the chemistry AT ALL and his guy that does is baffled by this. I've called several pool professionals and none of them understand. One doesn't do SWG at all and one that did had no idea that aeration raises pH so I wasn't trusting these people to help. I'm reticent to start manually chlorinating. I wonder if it's the filter running more often because of the termite swarms and bugs that occasionally end up in there, though the SWG is not running any longer because I drop the percentage.
chem geek: I actually never added acid when I didn't check the pH and TA after. The lowest I ever got it before a couple days ago was 50, when I added the borates, the pH was already crazy before that and the lowest I'd gotten it before that was 60, which isn't that low for SWG. A couple nights ago I got it to 20 but I immediately raised it up with sodium carbonate. Originally the Hayward Sense and Dispense used CO2 but apparently they use an acid tank now. I'm not sure why but I'd prefer the CO2 if it's possible to get though they may not support it. I want Hayward equipment because it's all controlled by the OmniLogic which I love.
onBalance: Thank you for weighing in. I can answer some of that:
1. The CH of the tap water tested at 175. The TA, as you mentioned, is 140, and the pH is higher than 8.2, though probably too much higher.
2. I don't know what the temp was like the day of plaster but it was probably around 70 to 80.
3. The salt was added within 24 hours of filling the pool.
4. I don't know but there was an unopened bottle of muriatic acid left behind so I'm guessing they used some beforehand. I will find out when I can get the pool builder to call me back. I'm having some difficulties there. New Orleans is an interesting place, to put it kindly.
Today, the TA is 100 and the pH is somewhere above 8.2. The Taylor comparator color is more magenta than the 8.2 test color. Haven't added anything since I put the PH up I added to correct for the most recent megadose of MA.