any way to control pH better?

[Furbabyvet]

Hi everyone. My pool water balance situation has improved greatly since I started BBB about 2 months ago. I took a water sample to the pool store(yeah, the one that messed me up so badly in the first place!) to cross check my numbers and the 20 year old slacker working there said I got an A+. Yea, me and yea, poolforum.com :). I didn't bother to tell him it was no thanks to his advice!

My numbers are approximately:
FC 5
CC 0-0.5
pH 7.7 today and rising quickly
CH 260
TA 80-90ish
CYA 40ish
Borates 40-50 ppm
temp. is 84-86 F
sorry for ambiguous #s but I have a hard time discerning the test result at times.

Anyway, I am happy with the way things are going except for two things. One is that there is still a very scant growth of green algae just above the waterline mostly on the "shady" side of the pool. It's only in a few places, not the entire pool. Raising water level an inch, shocking and scrubbing haven't made much impact on it. I've also tried adding polyquat 60, phosfree, and have now added borates to somewhere between 40-50 ppm. The algae is still there.

The other problem is that my pH keeps going up to 8 or greater, no matter what I do. We do have hard water in this area of AZ, but I was really hoping the borates would help slow down acid demand. The way it goes right now, I would need to add acid 2-4 times per week to keep it below 8.

Any ideas on either of these topics? Sorry if I posted in the wrong section!

Tabitha

[PoolDoc]

Hey Tabitha;

You'd gotten two earlier responses, from CarlD and Waterbear, that were sort of going at cross-purposes, so I'm jumping in here. I moved those posts to the China Shop for now. They are in the "Algae, TA or what" thread.

As I understand it -- please correct me if I'm misunderstanding -- you have two problems, one urgent and one longer term or chronic.

The urgent problem is the algae. If it gets away from you, you'll have serious problems, so we probably need to get that under control ASAP. More chlorine is the solution, at least right now.

The chronic or longer term problem is a continuing rise in pH. This problem may contribute to your algae problem, since chlorine tends to be less and less effective as the pH rises. So, lowering your pH -- regardless of how why it keeps going up -- is probably the next thing to do, after you get your chlorine level up.

So, let's do this.

1. Raise your chlorine level to 15 ppm, and then keep it above 10 ppm till the algae is gone.
2. Add enough acid to lower your pH to 7.2 or so -- but NOT all at once. If you know how to handle muriatic acid (no splashes, wear glasses, use gloves, don't breath the fumes) it's cheapest and best for your pool.
3. Don't try to fix anything else, till the algae is gone.
4. BUT, do collect the info we need to see if we can tell what's going on with your pH.

Regarding doses, I don't see any indication of pool size, but if you post gallons, we can figure doses or show you how.

If you're not doing so, make sure your pump is running 24/7, till the algae is gone.

As far is information goes, please do all the following (but take care of the chlorine and pH first):

1. Post pool gallons, typical timer 'ON' hours, filter type.
2. Tell us what sort of chemicals you are normally using (labels, chemical ingredient)
3. Tell us what's been happening with your TA -- has it always been this low, or has it been going down lately?
4. Test your FILL water for pH, chlorine, Alk, Calc, and post those results.
5. Tell us if there is anything connected to your pool that would aerate the water (fountain, waterfall, spillover edge, attached spa, air jet, etc.)

And, let us know you have a problem with any of this.

Good luck!

Ben
"PoolDoc"

[Furbabyvet]

Hey, thanks a lot for the help.

1. Pebble Tech pool. 11,940 gallons. Sand filter. Pump runs 7 hr. during the night and 1 hr. during the afternoon.
2. I use 10% chlorine, 29% muriatic acid regularly. I have 2 trichlor pucks in my floater right now to help with chlorine and to add CYA. I have also added borax. As I mentioned, I’ve put in polyquat 60 a few times—once I put in a whole bottle, but then later just a few ounces per week. A month or so ago was the last time I added PhosFree just because we already had it from last year.
3. 6 weeks ago, the TA was 230. I followed the procedure outlined here to get it down so I could add borax.
4. FILL water pH 7.6, Cl 0.5, TA 110, CH 250.
5. There are no water features in the pool, although we have a “aerator” nozzle that can be turned on as needed. I only used this when trying to lower the TA.

My water test today:
FC 6, CC 0, pH 7.8, TA 90, CH 280, CYA 40, Bor. 40

I have the solar cover on and the water temp at 7:30 am is 83 F.

The algae is still there, although not as bright green as it has been at times. It is about 3/4 of an inch ABOVE the water line. Will I need to fill the pool more to affect this algae or will it get enough chlorine as is?

Two months ago, I fought off what I believe to have beeen mustard algae in the form of brown “dust” that had been there for over a year but I didn’t know what it was. There is no sign of the brown dust and the pool water is as clear as clear can be.

Tabitha

[PoolDoc]

FACT #1: I have the solar cover on and the water temp at 7:30 am is 83 F.

The algae is still there, although not as bright green as it has been at times.

FACT #2: It is about 3/4 of an inch ABOVE the water line.

Ok. I think I've got the picture.

As a general rule, when you are trying to fix anything with your water, your pool needs to be on 24/7. But, in your case, the problem is OUT of your pool, not IN it. And, since the chlorine is IN your pool, neither it, nor any algicide will do the trick.

Is your solar cover the type that you trim to fit? If it is, have you trimmed it to fit, so it ONLY floats on the water, and doesn't cover the edges at all?

PoolDoc

[Furbabyvet]

Ok. I think I've got the picture.

As a general rule, when you are trying to fix anything with your water, your pool needs to be on 24/7. But, in your case, the problem is OUT of your pool, not IN it. And, since the chlorine is IN your pool, neither it, nor any algicide will do the trick.

Is your solar cover the type that you trim to fit? If it is, have you trimmed it to fit, so it ONLY floats on the water, and doesn't cover the edges at all?

PoolDoc

I think I overstated the distance of the algae from the waterline. It's more like 1/4 inch above and it's in small patches, in the pits between the pebbles. It does seem to be wet in that area, though.

The solar cover is a trim-to-fit type that floats on the water. I only put it on yesterday, so it is definitely not the cause of the algae that's been there off and on for weeks.

I went ahead and brought the Cl. level up to about 18 ppm and the pH is somewhere around 7.4 and going down as I add a little acid at a time. The cover is still on-- should I take it off? Doesn't seem like it will affect what I'm trying to do.


Tabitha

[PoolDoc]

Hi Tabitha;

Be cautious about your pH. As your chlorine level goes above 10, your pH readings, if measured with phenol red drops, will be less and less accurate. At 18 ppm . . . unless you are using a calibrated pH meter, you really don't know what your pH is.

Regarding the algae -- are you saying that you have algae in the pits and rough places at the water line?

If so, lowering the water level, and using a 1:10 spray of polyquat will probably work. Just make sure you use a CLEAN sprayer, with no herbicide or pesticide residue.

Or, if you've got an old clean sprayer that you don't mind ruining, spraying with straight bleach, and then 'pressure washing' with a hose and nozzle and the re-spraying will probably work.

But, it depends on how deep the rough spots are: you can only kill algae you can reach!

Once the algae's gone we'll need to see what the situation is with your pH.

Ben
"PoolDoc"

[Ohm_Boy]

Pump runs 7 hr. during the night and 1 hr. during the afternoon.

I'm gonna jump in here and reinforce that your pump needs to be circulating 24/7 while you are trying to clear up algae. Lack of circulation can make algae VERY hard to get rid of.

[Furbabyvet]

Hi Tabitha;

Be cautious about your pH. As your chlorine level goes above 10, your pH readings, if measured with phenol red drops, will be less and less accurate. At 18 ppm . . . unless you are using a calibrated pH meter, you really don't know what your pH is.

Regarding the algae -- are you saying that you have algae in the pits and rough places at the water line?

If so, lowering the water level, and using a 1:10 spray of polyquat will probably work. Just make sure you use a CLEAN sprayer, with no herbicide or pesticide residue.

Or, if you've got an old clean sprayer that you don't mind ruining, spraying with straight bleach, and then 'pressure washing' with a hose and nozzle and the re-spraying will probably work.

But, it depends on how deep the rough spots are: you can only kill algae you can reach!

Once the algae's gone we'll need to see what the situation is with your pH.

Ben
"PoolDoc"

OK, I'm gonna leave the pH alone for now, then.

Yes, the algae is in the very shallow pits (maybe 1/16 of an inch deep or less) that exist just above the waterline where calcium has built up and is rough because of the pebble tech finish.

I thought about spraying/scrubbing with bleach, but wondered why the stuff is there in the first place??? It is about 105 degrees here today and very low humidity. I've kept the chlorine levels in the range recommended her for my CYA levels. Why the heck are these little splotches of algae hanging on? I am hoping this round of shocking will kill it once and for all.

Back to the original question: any ideas about why my pH level goes up so fast? I've been taking it down around 7.6 but it is up to 8.0 within 3-5 days. The fill water is around 7.6, so I am not sure what's going on. Is it the relatively higher chlorine levels (not shock level) making it test higher than it really is?

Thanks!

[Furbabyvet]

I took some photographs:
http://www.flickr.com/photos/40043936@N04/?saved=1

[PoolDoc]

Some forms of algae seem to be able to create something like 'roots' into porous plaster and concrete surfaces. If you've got pits, you've probably got porous plaster. Once those forms of algae are established, killing the visible algae is sort of like mowing crab grass. You STILL haven't got the roots.

Unfortunately, there are no 'herbicides' for algae that will reach into the roots.

Once a penetrating algae is established, management is more a matter of control, rather than eradication.

You could do something like raising the water level to completely cover the algae, and then raising your chlorine level to 50+ ppm (no misprint - I mean "50") and holding it there for a week or so. That might kill all the algae. Or, it might not.

You can acid wash, which may remove the algae, but at the price of making your plaster even MORE porous than before, and thus more susceptible to NEW algae.

You can coat the pool with epoxy paint, which algae can't easily penetrate or grow on.

But, for this season, the practical think is control, not eradication.


Regarding pH, the short answer is, "I don't know why your pH keeps drifting up".

There are many possible factors. If you aren't using a kit with Taylor based reagents, sometimes as little as 3 ppm can mess up readings. But, that wouldn't cause a apparent rise, unless you raised your chlorine too.

If your pool is relatively new, changes in the plaster can cause changes in pH.

Or maybe, if you are using something besides trichlor tabs (which are acid) but have gotten a hold of some calcium hypochlorite tabs, that can raise pH.

Or something else.

I can observe that, in my experience with multiple large commercial pools managed with sodium hypochlorite (bleach) feed systems, I universally found that bleach fed pools 'wanted' to be at a pH of 7.6 or higher. I have no analytical explanation for this. But I can tell you that I discovered that if I let the pH float upwards, it usually -- but not always -- stopped before 8.0. I also found that if I operated the pools between 7.6 and 8.0 it took FAR less acid, than if I tried to operate the same pool between 7. 2 and 7.6. (Note to Chem Geek: yes, I tried it both ways on the SAME pools :confused:)

I never tried to mix trichlor and bleach -- not sure why you'd do that -- but regardless, you may find that your pool has some point below 8.0 where it will 'rest' or you may find that if you operate in the 7.6 - 7.8 range, it will continue to require acid additions, but only small ones.

If you run at higher pH, you'll need to compensate by running slightly higher levels of chlorine.

On another related note: buffering has to do with how difficult it is to change the pH of a solution (your pool water in this case). Highly buffered water has highly stable pH . . . . IF the buffer in question is effective at that pH level.

Most buffers have ranges over which they are effective, and other ranges over which they are not so effective. Cyanuric acid is an effective buffer at LOW pool pH levels, below 7.4 as I recall. Borax is an effective buffer at HIGH pH levels, above 8.0, I think. Total alkalinity tests measure how much buffer you have, but not which levels it's effective at.

This is important, because if you have drifting pH levels like you do, it's your pool's buffer system that determines how hard you'll have to work to maintain your pH level. Absent aeration, sodium bicarbonate is an effective buffer in the 7.0 - 8.0 range where your pool lives. A pool with an effective bicarbonate based "Total Alkalinity" will require larger doses of acid, added less frequently, compared to a pool without that bicarbonate based buffer.

More or less, a well buffered pool will require that you adjust your pH less frequently than a poorly buffered pool. It won't really decrease how much acid you need, but it will change how often you have to add it!

This doesn't matter on a pool with a stable pH -- if the pH is not moving, you don't need something (an effective buffer) to keep it from moving fast. But on your pool, it does matter.

For that reason, I wouldn't recommend trying to replace your bicarbonate buffer system (effective in the pool pH range) with a borate buffer system (not so effective in the pool pH range). But it's up to you. You can run the pool successfully either way.

Best wishes,

Ben

[PoolDoc]

Just saw the photos -- so-called black algae.

And, with an eroded pebble finish like that, you've got a long term maintenance issue.

Could you mail larger versions of those photos to me at poolforum AT gmail DOT com?

I'd like to edit them, comment on them, and repost them here. I can explain a bit more of how and why, and what to do, if you do (BLACKMAIL, here! ;) )

Ben

[dhanger]

PoolDoc-

I just wanted to comment something about the surface, I'm in AZ too, and it seems to be a real popular finish here, the PebbleTec. It's not eroded plaster, as you seem to think (I don't mean to insult your intelligence if you already know what I'm talking about), which is a small pebble inlay with concrete or grout as a binder surrounding it. The difference in depth between the top of the pebbles to the binder is no more than 1/32". I have no idea whether that would affect your diagnosis or not, but I thought it might be helpful to clear that up.

Dan

By the way, I have the same issue regarding pH rising, in my 5 years with this pool, not once have I ever had to raise it, always lowering. Don't know if that has something to do with the water here, the environment, or what.

[PoolDoc]

No insult taken . . . I didn't actually think Pebbletec was eroded plaster, but I've seen pools with, hmmmh, shall we say raggedy edge finishes, so I didn't want to get too specific. The bottom line for me, when I'm posting here, is that I'm usually pretty conscious that I don't really know what the poster actually has on, or in, or around their pool.

In this case, seeing the pictures was really interesting. I hadn't realized that you'd get waterline deterioration of the interstitial filler in Pebbletec like his pictures show.

By the way, do you happen to know the actual chemical or mineral composition of the "pebbles" and of the filler?

PoolDoc

[dhanger]

Well, according to their website-

"Created with pebbles from around the world that are selected for their color and beauty."

So, if they're telling the truth, they are actual pebbles and not some composite. I can't say what the filler is, but it appears to be concrete. Seems I read once how they apply it, a layer of concrete with the pebbles mixed in, then at a point they gently wash off the concrete exposing the pebbles. Can't find that info now, so not sure I have that right.

And, I'm not convinced there is any deterioration going on there. The photos look exactly like mine (minus the black deposits), in fact it looks like there is a calcium ring exactly like mine, that may be what's making it look like deterioration.

Dan

Edit-Actually, the more I think about it, the filler probably wouldn't be concrete as the aggregate would be exposed as well. Guess I have no idea what it is, unless it's just the cement used in concrete, or mortar.

[Furbabyvet]

Ben, I will email the pics to you.

Dan is right in his description of my pool. There is a pretty thick build up of calcium on the pebbles just above the waterline. It is higher in relief than the pebbles below the waterline. Both my neighbors have the same thing on their Pebble Tec pools, so I think this is sort of "normal" for this area. I have a similar build up on the inside of my glass shower door despite having a water softener, but that is an entirely different rant...

EDIT: the algae appears to be green, not black. I doubt this makes much difference in this conversation.
Maybe we will try lowering the water a bit and blasting the algae with 50:50 bleach every time we can and see what happens! Thankfully, it's not around the entire pool. We had this algae worse last year but it seemed to go away, especially when I shocked the tarnation out of it in June (60 ppm-- oopsy) but alas, I guess there were microscopic roots in there.

As an aside, I am using trichlor and liquid chlorine only because I already had the trichlor from last year and I need more CYA in the pool, so I thought I might as well use them up.

Hmmm. I was really thinking the borates were going to help stabilize my pH. Is this hopeless, or should I put some more in? The info here suggests 50 ppm but I stopped short at about 40 just to be cautious.

Tabitha

[CarlD]

I'm not sure why a direct application of bleach to the surface won't at least control it.

[PoolDoc]

Carl, there are a couple of reasons why you might not want to apply bleach directly on a regular basis.

First, simply applying it regularly is a bit of a challenge.

If you pour, you're likely to end up with it on your self. And unless you're doing it naked (but in sun glasses or safety glasses) you're going to tear up clothes. There's something about bleach that just wants to 'reach out and touch' some cotton or Lycra. After working with the stuff for 20+ years, I've thrown out boxes of clothes . . . and I've STILL got holes in just about everything I wear in the summer.

You can get bleach tolerant sprayers. But they're hard to find and in my experience, sometimes not as bleach tolerant as you might think.

Second, if you pour, instead of spraying, you're likely to end up overdosing your pool. Pouring bleach all the way round a pool, I personally would probably end up dumping a gallon or more in the water.

Finally, I'm not sure what it would do the surface. Bleach is a high pH solution, and stuff evaporates RAPIDLY in Arizona, due to the low humidity. Without prior testing, I'd be afraid that some sort of scaling or discoloration might occur on the surfaces wetted directly with bleach.


Using a polyquat mixture in a sprayer is not likely to result in any of these problems.

But . . . from a purely "kill the algae" point of view, putting bleach on it regularly should work fine.

PoolDoc.

[CarlD]

I know we've used bleach in empty Fantastic spray bottles to get at mold and mildew in showers and tubs forever. Even have one now, with "BLEACH" written on it with a Sharpie.

Why not use that? A pint or quart pump sprayer--if it doesn't hold up, you just throw it away. I've ruined my share of pants, shorts and shirts as well! I think if I go near the pool wearing a new Lacoste shirt again my wife WILL murder me! :eek:

Plus, you know I'm a BIG fan of Polyquat as one of the two chemicals pool stores sell I appreciate! (the other is CYA, as needed).

[PoolDoc]

If you've got disposable sprayers, and they work long enough -- that would be fine.

I'd still want to dilute the bleach, until I was pretty sure it wasn't going to result in some sort of new and 'special' scaling or discoloration of the surface.

Ben

[PoolDoc]

OK, here's one of Furbyvet's pool pictures with my notes and editing:

http://www.poolforum.com/pf2/picture.php?albumid=9&pictureid=76

Several things to note:

FIRST: Black algae isn't; it's dark green. It appears black when it's thick, or underwater. But if you'll use the 'smear test' -- scrape some with your fingernail, and then smear it on a white card -- it will always appear green to dark green.

SECOND: The scale visible at the top may be calcium carbonate, or it may not. In the Southwest, their drinking water is sometimes so full of minerals that people can 'mine' it! As a result, they can get quite creative with their scales! The easy test is acid: if you flake off a bit, and drop some muriatic acid on it, it will foam or fizz if it is calcium carbonate.

THIRD: Exposed mortar grooves -- between tiles, between pebbles, in cracks and crannies, around light niches or skimmers is algae's refuge. It's always difficult, and sometime impossible, to get enough chlorine or other algicide into those spots to kill off the algae. In this part of the country, I wouldn't even consider a commercial pool management contract on a pool with a surface like that, unless the customer accepted a VERY large algae management surcharge. There's no shortcut to physical cleaning, and you have to do lots of it on a heavily loaded commercial pool with a low quality surface (= equals any surface with LOTS of algae hidey-holes). Very, very expensive glass tile pools, with poor quality grout joints (= rough and/or porous) can be a total nightmare to maintain. Beautiful, but extremely 'high-maintenance'!

FOURTH: What's particularly interesting here is that Furbyvet's algae has found a home at the 'high tide line', where it's wet enough to live (because of the grout joints holding moisture) but low enough in chlorine (because it's outside the circulation system) for the algae to be quite happy.

FIFTH: People, including some pool book writers, often think that black algae or mustard algae or green algae is a species of algae. But, in fact, the names are nothing but a physical description. Black algae is black looking, and surface clinging. Green algae is free floating and not obviously connected to the biofilm layers associated with it. But, in fact, all forms of algae tested by some researchers I've spoken to in the past, were FAMILIES of both bacteria and algae. This is especially true of any biofilms, like the slime that precedes green algae outbreaks, or like black algae. My recollection is that the lowest number of identified species in any single occurrence was over 20, and always included both algae and bacteria.

PoolDoc

[Furbabyvet]

Update: after keeping the chlorine at shock level for a couple of days, keeping the cover on the pool and scrubbing the algae with concentrated chlorine and a steel brush, I can't really see any algae any more. I know it may still be lurking, so I will keep my eye on it.

Thanks again for the help...

[PoolDoc]

Sounds good!

Thanks for the follow up info.

Ben

[waterbear]

I can observe that, in my experience with multiple large commercial pools managed with sodium hypochlorite (bleach) feed systems, I universally found that bleach fed pools 'wanted' to be at a pH of 7.6 or higher. I have no analytical explanation for this. But I can tell you that I discovered that if I let the pH float upwards, it usually -- but not always -- stopped before 8.0. I also found that if I operated the pools between 7.6 and 8.0 it took FAR less acid, than if I tried to operate the same pool between 7. 2 and 7.6. (Note to Chem Geek: yes, I tried it both ways on the SAME pools :confused:)
I have seen the same effect on customer's pools with SWGs and on the commercial pools with bleach feed systems also, and have discussed this before on different forums.



Most buffers have ranges over which they are effective, and other ranges over which they are not so effective. Cyanuric acid is an effective buffer at LOW pool pH levels, below 7.4 as I recall. Borax is an effective buffer at HIGH pH levels, above 8.0, I think.
At normal pool pH range most of the borate/boric acid buffer is in the form of boric acid and has a downward effect on pH when it starts to climb as opposed to the bicarbonate/carbonic acid buffer which causes ph to move toward 8.2




Just my 2 cents.

[Furbabyvet]

Another late update on the waterline algae problem. After using the BBB method all summer and attacking one more algae bloom (due to landscaping debris left in pool too long and my negligence), the waterline algae is completely gone. We did scrub with bleach, but I think it was just having balanced water over time that really fixed it.

I'm still amazed at how stable our pool has been using these simple concepts. Now that we have things under control, we're gonna try a SWCG to indulge my laziness even more. Ya'll are great. Thanks a million!

Tabitha