CH rising?

[DONNIE]

What would cause my CH to rise from 410 to 480 in 19 days? I have added nothing but bleach and muriatic acid in that time.

Temp 41
PH 7.6
FC 6
CC 0
CYA 60
CH 480
TA 70 (down from 80 in same period)
Salt 3600


Donnie

[chem geek]

Assuming that there was nothing wrong with the test for CH itself, the CH will rise if the plaster is curing since that releases calcium hydroxide into the water (it will also make the pH rise). If your plaster is more than one year old, then it is unlikely to still be curing (at least not that fast). If the CH rise was accurate and truly due to the curing of plaster, then you would have added 23 cups of Muriatic Acid to compensate for the very strong pH rise. I doubt very much that you've added anywhere near that amount of acid so I doubt the curing of plaster is the cause.

The other way that CH can rise is if your water chemistry is in a corrosive state with too little dissolved calcium carbonate. Your water is, in fact, slightly corrosive, but only a little bit (-0.3) and not nearly enough to cause etching or dissolving of the plaster at the rate of CH change you are seeing. If the CH rise was accurate and truly due to corrosion of plaster, then you would have added 23 cups of Muriatic Acid to compensate for the very strong pH rise (just as above for curing of plaster), but you would also have had to outgas a whole lot of carbon dioxide as well. Again, a very unlikely scenario.

Your TA is dropping because you are adding acid to maintain pH and the pH may be rising (until you add acid to lower it again) due to outgassing of carbon dioxide, but this does seem strange unless your water is getting aerated. I assume your SWG is off since the water is so cold (and you said you were adding bleach) and I assume you have waterfall or fountain features probably turned off or not running for very long. If your TA truly dropped 10 ppm (it could have been less since the test only resolves to 10 ppm for one drop), then the pH would have first risen from 7.6 to 8.67 due to carbon dioxide outgassing and you would add 2.9 cups of Muriatic Acid to restore the pH (of course, you would acid more frequently and not see the pH rise so much). That sounds a little closer to what is really going on except I suspect you added less acid and had less actual drop in TA. Of course, that only explains the TA and not the CH.

It is very unususal for the CH to rise so quickly. I would suspect that there is something about the test that is off a bit. Maybe it is sensitive to temperature -- the pool water is cold so let it get to room temperature before testing. With my own testing I used to get a "fading endpoint" which made the counts of the last drops difficult, but then read the instructions that said to add a few drops of titrant first before the calcium buffer and indicator solutions and that helped make the endpoint much more obvious and consistent.

So, bottom line, I don't have a good answer for you (but you know how I like to write...)

Richard

[CarlD]

What would cause my CH to rise from 410 to 480 in 19 days? I have added nothing but bleach and muriatic acid in that time.

Temp 41
PH 7.6
FC 6
CC 0
CYA 60
CH 480
TA 70 (down from 80 in same period)
Salt 3600


Donnie

Is your pool gunite/concrete/plaster, etc? That can do it, ESPECIALLY if it's new. If it's a vinyl pool you should be ok, especially with your T/A so low. In a vinyl pool, if your CH reaches 500, and your T/A gets high then you can end up with cloudy water.

Let us know which it is.


And Chem_Geek responded first!

[DONNIE]

#1 my pool is fiberglass. I have been adding 7oz of acid every other day to keep my Ph at 7.5 but in the last week it has been stuck at 7.6 so I just leave it there. I assume thats dut to the lower TA. My SWG is off and I have had to add very little bleach to maintain 5ppm FC. Air temps have been below freezing here for most of the last 6 weeks so I have had a fountain and pool pump running 24/7. Water temps for the last 6 weeks have been between 37 - 45. I did test the CH last night right out of the 41F pool.

Donnie

[chem geek]

Wow, that's still a lot of acid you've added. 7 ounces every other day would be over 8 cups of acid over the 19 days. Since only about 3 cups would be needed to have the TA lowered by 10 ppm, it could be that the TA test is measuring a little low so it's more like a 15 ppm or so drop. That still only accounts for about half of your pool's acid demand. At least your 24/7 use of the waterfall explains why you have to add acid and see a TA drop. What is still not explained is the additional acid demand and the increase in CH. I'll bet it's the water temperature since you did the test without letting the water get to room temperature. Try doing that the next time(s) you test and let us know if it is still rising.

By the way, it is not necessary for you to keep your pH as low when the water temperature is cold. Natural water balance will have the pH rise from 7.5 to 7.7 when the water temperature drops from 80F to 50F so you could keep your pH at 7.7 to 7.8 and probably need to add a lot less acid to keep the pH there. Your water chemistry would be more in balance at the higher pH, though it's not very far out of balance now (so the main reason to do this is to lower your acid demand since you have to keep the water flowing to prevent freezing).

I still wonder where the extra acid demand is coming from. One drop in a TA test isn't very accurate so perhaps over a longer period of time the results will make more sense.

Richard

[DONNIE]

I think I have been trying too hard to keep the Ph at 7.5 so every other day when it hits 7.6 I add the 7oz of acid. Last week I wanted to see how high it would go left unadjusted. To my suprise it has remained stable at 7.6 and I haven't had to add any all week. I'll retest the Ch tonight at room temp. Thanks for your advice.

Donnie

[chem geek]

A change in pH from 7.5 to 7.7 might cut down your rate of CO2 outgassing by almost half and cut the acid demand in half, but a change from 7.5 to 7.6 shouldn't be so dramatic as having virtually no pH rise in a week. I'm sure something else has happened coincidentally (maybe something simple like there is less wind). At any rate, the point is that you can live with a higher pH and this will have you add less acid and that is what you are seeing (albeit more extreme than expected).

Richard

[DONNIE]

Can you actually "smell" out-gassing? thought I could smell my pool the other night for the first time.

[chem geek]

Carbon dioxide is odorless so you can't smell it. If you are smelling chlorine, then that is possible (a "clean" chlorine smell unless you have combined chlorine), but I'm not sure why you'd be smelling that now all of a sudden.

Richard

[DONNIE]

Im not even sure it was my pool. Zero CC's. It's been really wet and cold here so Im sure it was just the weather. That or the Opossum thats been hanging around.

Donnie

[CarlD]

I, on the other hand, am baffled by the rising calcium hardness. Nothing you are doing should cause that.

So...Next question: Is your waterfall fiberglass, too, or is it stone and even mortered?

[chem geek]

Carl,

That's an excellent question (and I, too, look forward to hearing the answer) because normally the slightly corrosive water wouldn't be expected to dissolve calcium carbonate, but perhaps the extra physical erosion of a waterfall might accelerate that process. The problem is that the amount of calcium rise he is seeing is inconsistent with the amount of carbonate that must also be introduced and this should increase the TA and pH and require a lot more acid than is being added to have his TA actually drop from 80 to 70.

If I use the pool numbers given, then adding 7 ounces every other day for for 19 days is 8.3125 cups of 31.45% Muriatic Acid. I can then reproduce maintaining a pH of 7.6 and having the TA drop from 80 to 70 if I assume corrosion of calcium carbonate of 18.9 ppm and a large outgassing of carbon dioxide.

So SOME increase in calcium of around 20 ppm can be explained through corrosion, but not an increase of 70 ppm unless there is some strong acid somehow getting added to the pool (which I doubt -- beyond the Muriatic Acid, of course). I'm betting that the calcium test is off a bit, possibly due to temperature dependence and I'll be eager to see his new measurements.

Richard

[CarlD]

But if it's ALL fiberglass, where the HECK is the Calcium coming from??????:confused:

[DONNIE]

My fountain is called a Wok Waterfall. It's basically a 36" wok shapped dish that cascades into the pool with a fall of about 10". It is made entirely of fiberglass BUT...I have put 24 pounds of smooth, flat river rock in it mainly just for weight. Probably 24" diameter and 3" deep. I will retest tonight and post the results. Could the rocks be a source of calcium? I don't believe they are very porus. Each is about 2 to 3" round and 1/2" thick.

Donnie

[chem geek]

If the rocks are like those found in river beds, then they don't dissolve much and are composed of many different minerals, not just calcium carbonate. If they are more like limestone, then certainly soft limestone can wear quickly and is composed mostly of calcium carbonate. Personally, I doubt that the rocks are contributing much to the calcium so my take is that the test is wrong for whatever reason and that the calcium did not in fact increase over that short period of time.

Richard

[DONNIE]

I'm hoping your right. We'll see tonight.

[DONNIE]

Ok. Ok. Took extra care to fill my test bottle to exactly 25ml. Let stand (capped) for 1 hour to get to room temp. Added 2 drops of titrant before test. Added the 5 drops of blue which took about 30 seconds to totally mix. Started adding my drops very carefully to be exact. At drop 41 (counting the first 2) it turned slightly purple. drop 42 turned a distinctive blue. Drop 43 & 44 produced no change. So voila...CH=420ish. I guess the 41 degree water made the difference. Or maybe it was the wine! Lesson learned. DONT TEST 41 DEGREE WATER! Thanks Richard. Thanks Carl. I appreciate the concern and especially the guidance.

Donnie

[waterbear]

I've said it before and I will say it again, water temp makes a difference. If you compare test results done of 75 deg water and 45 deg water you will be comparing apples to oranges! Taylor doesn't really specify a temp at which the tests should be done (to the best of my knowledge) but LaMotte does state that their reagents are formulated to produce accurate results between 70 and 80 degrees.

[DONNIE]

Just for kicks I tested Ph, FC & CC last night both at 41 degrees and a couple of hours later (from a sealled container) at room temperature, aprox 72 degrees. All tests came out exactly the same. I know now not to test CH and TA unless they are at room temp as the results come out completley different that at 41 degrees. I havent tried salt at the two different temps but my test at 41 degrees and my SWG are the same. In the future I will always test at room temperature to get consistent results. Thanks Guys.

Donnie

[waste]

Donnie, you're doing a great job with your new pool and thanks for the input!

[chem geek]

Donnie,

Great minds think alike. I did exactly the same thing after you posted your CH results. Like you, I found that chlorine tests did not appear to be temperature dependent. In fact, the chlorine test seems to be TIME dependent where waiting too long to do the test has the chlorine level drop so it's more important to do the test quickly than to have it be at room temperature.

I did not get the same results as you did with the pH test. I found the pH to drop as the water warmed up and that is actually what I expected since there are technical reasons that should be the case. It doesn't drop that much, however, since it theoretically is only around 0.1 unit from 50 to 70, but from 45-50 to 85 it should be around 0.2 units which is much more noticeable. I heated the sample in my hand to simulate "heated" pool water and got the pH to drop more noticeably (I also kept the container covered during the test to prevent "natural" pH rise from outgassing).

I also didn't find as much variation as you did with the CH test. I did find a small variation, but only a couple of drops difference (i.e. 20 ppm) which isn't much.

I am somewhat conflicted regarding recommending that ALL tests be done at room temperature. I think the pH test is best done at actual temperatures since pH is supposed to vary with temperature and the chlorine test loses accuracy if you wait too long. So perhaps, all tests but pH and chlorine should be done at room (or "warm" water, if in the summer) temperature or if you let water warm up for the chlorine test -- cover the container while waiting.

Richard

[DONNIE]

Richard, Do you use the standard Taylor Ph color test or do you use something more elaborate? I may have had a small difference but not a noticable one. What do you anticipate the salt test results will be a cold vs warm temps will be?

Donnie

[DONNIE]

Thanks Waste. I'm really having fun now that I am understanding whats going on with my pool. It's really a fairly basic science that everybody (including myself) finds overwhelming at first. The more I learn, The easier it becomes.

Donnie

[chem geek]

Richard, Do you use the standard Taylor Ph color test or do you use something more elaborate? I may have had a small difference but not a noticable one. What do you anticipate the salt test results will be a cold vs warm temps will be?

Donnie
I just use the standard Taylor pH colorimetric (i.e. "match the color") test. I did a salt (chloride) test on my pool, but only did it at one temperature. I was surprised to find that I had between 800 and 1000 ppm salt in my pool since I effectively diluted by 50% twice two winters in a row, though not last winter nor this winter, and I've only used chlorinating liquid -- only about 0.5 ppm per day in the summer and hardly any demand at all in the winter. So I expected around 500 ppm or less. I must have had a MUCH higher TDS than I thought in the past. Either that or the salt test is temperature dependent. My guess is that it isn't. The silver nitrate is a pretty strong one-way reaction so I wouldn't expect the indicator change to be very temperature dependent. Of all the tests, it's the CYA test that is probably the MOST temperature dependent (due to the partial solubility of melamine cyanurate, though see this post (http://www.poolforum.com/pf2/showpost.php?p=42112&postcount=8) for more info about that).

Richard

[CarlD]

Posting at 3:53am? Richard, you're too much into this for the winter!

Remember one thing about the salt: The "inert ingredient" in Liquid Chlorine/Bleach is, of course, brine/saline/saltwater. That's probably the cause of your salt rising.

Bleach is made from saltwater.

[chem geek]

Posting at 3:53am? Richard, you're too much into this for the winter!

Remember one thing about the salt: The "inert ingredient" in Liquid Chlorine/Bleach is, of course, brine/saline/saltwater. That's probably the cause of your salt rising.

Bleach is made from saltwater.
It was 12:53 AM on the west coast where I am, but you're right, that's still late.

I figured with the 0.5 ppm FC average addition per day and that 1 ppm FC adds 1.6 ppm of salt (0.8 ppm from chlorine that becomes salt when it gets used up plus 0.8 ppm of salt directly) that over 7 months of summer use that is 0.5*1.6*7*30=168 ppm. I guess two seasons of that plus the small amount over winter plus what was leftover and diluted from previous seasons plus the 280 ppm from the Calcium Chloride adds up to at least 616 ppm. If I had around 200 ppm leftover from previous seasons diluted in half each season that gets me to over 800 ppm. When I did the math last night, it didn't work out, but then again that's what I get for trying to "think" at 12:53 AM!

So cool. Now I've got one of those near-1000 ppm salt pools. I wonder if my wife will notice anything different.

Richard

[CarlD]

Wait a minute, just a doggone minute!:confused:

Did you say SEVEN months of summer use a year???:eek:

With a lot of luck we can maybe get 4 1/2 months of use a year: Most of May, all of June through August, and maybe half of September, if and only if it's not raining all month. And that's WITH solar panels! Without, it would be part of June, and July and August.:mad:

You really know how to hurt a guy from New Jersey, don't you!:(

[chem geek]

Carl,

If it makes you feel any better, from mid-April to mid-May and from mid-October to mid-November we heat with lots of gas assist and it's EXPENSIVE, a few hundred dollars for each month. So we really only have FIVE months of true solar-only heating time and we still have a few days here and there where we use gas assistance since we keep the pool at 88F if we can (or at least 86F). I think we only use NO gas for a month in July. All other (swim-season) months have at least one day that needs gas due to the sometimes cloudy day or long foggy morning. If I really wanted to make you jealous, I'd be living in southern CA or AZ or southern FL.

Richard

[DONNIE]

88 degrees sounds warm. I haven't even been in mine since construction but hopefully anyday we will get out of this deep freeze. I have a 200K btu heater that I hope wont be too expensive to heat 9K gallons so we can use ours mid March thru September.

Donnie

[waterbear]

Carl.
Hate to make you feel even worse but how about 9-10 months a year (with the heatpump going for about 4-5 of them). Oh, the hottub gets used in the other 2-3 months! This is why I no longer live in New Jersey ;) I hope to add solar in the next few years once my piggy bank recovers from the pool builder from h*ll that I still am fixing so don't begrudge me this one!:D

[CarlD]

Oh,
I'm just sitting here watching this ice storm shut down the state...How you can have an ice storm when it's 17 deg F is a mystery to me---that's 10 to 15 degrees too cold. But Hey! This is New Jersey! Our state flower is Poison Ivy. Our state bird is the greenhead mosquito.

But we are getting this nasty dangerous wet sleet. Even snow is easier.

We live in New Jersey because it's better to live in the Jughandle State than the Ripoff State (NY--where I was born and grew up). We pay high taxes, but lower than NY. NJ is actually an economic powerhouse and housing prices are STILL going up. Our public schools are among the best. All the drug companies are here in a big way, there are the oil refineries over on the coast, and it's all within easy reach of NYC and Philly, not to mention the vacation areas here, in PA, NY, Ct, and Mass.

While it's very densely populated, especially the eastern side of the state, people don't think to move here...that's OK with us!

We used to live on 4 acres further west. It was beautiful, on what passes for a mountain here, with all kinds of wildlife--the black bears were quite the nuisance. Even here in the 'burbs the deer are like pigeons and the wild turkeys show up regularly.

If you move to NJ, be sure to live on a hill, not a flood plain, and REALLY learn defensive driving! The NJ drivers are bad but the New York and Pa drivers are really crazy!

[waterbear]

Carl,
I was born in Millburn (NOT Short Hill, which used to be a part of Millburn, that was the NEW money. My parents lived in the Estates). It's a beautiful state! I can remember seeing deer and other wildlife nearby and can still remember the Maple trees everywhere and the Oaks! (Florida just has a lot of pine and mangrove, it's not all Palm trees like you northerner's think!) One thing though, the people that live in NJ have finally seen the light at the end of the tunnel and it has them very upset.....
they realize it's New York!
(Appologies to any New Yorkers out there but I just couldn't resist this joke....at least it's not as bad as the one about the Jersey girl and the garbage.:eek:)

[waste]

Evan, what's the difference? (sorry to blow your 'punchline') FWIW - I grew up in N NJ, so I can say what I want to about the 'armpit of america'.
Truely, NJ is a beatiful state, if one takes the time to go a little way off of the interstates.
For all in the NE, enjoy the long awaiated snow/ ice (to y'all in more southern or western climates - *&()^%$ - um, I mean, enjoy your 'non iced over' pools) :D

[edit]Evan, my kin come from Short Hill, and I think thier money was old before Millburn was established ;) , but you're right, get a few miles off of the highway and anyone would realize why it's called the 'Garden State' [ silly me -end edit]

[CarlD]

Oh No!!!! You guys are gonna get people thinking they need to move here! We are already the densest state in the union...Think Sopranos and "Fugeddaboudit" and Joe Piscapo...and the Turnpike..

[aylad]

Oh No!!!! You guys are gonna get people thinking they need to move here! We are already the densest state in the union...Think Sopranos and "Fugeddaboudit" and Joe Piscapo...and the Turnpike..

No, thanks...I'd rather stay down here and enjoy my non-iced-over pool that I get 7 months a year use out of...without a heat pump! :)

Jan

[waterbear]

Evan, what's the difference? (sorry to blow your 'punchline')

You asked for it then--the garbage gets taken out once a week!) FWIW - I grew up in N NJ, so I can say what I want to about the 'armpit of america'.
Truely, NJ is a beatiful state, if one takes the time to go a little way off of the interstates.
For all in the NE, enjoy the long awaiated snow/ ice (to y'all in more southern or western climates - *&()^%$ - um, I mean, enjoy your 'non iced over' pools) :D

[edit]Evan, my kin come from Short Hill, and I think thier money was old before Millburn was established ;) , but you're right, get a few miles off of the highway and anyone would realize why it's called the 'Garden State' [ silly me -end edit]
When I was a kid I can remember when most of Short Hills was being built! (Before the Sorpranos moved in there) Short Hills started as the 'new' section of Millburn before it broke off and became it's own town. This is why the 'Millburn Mall' is actually located in Short Hills (or have they finally changed the name to Short Hills Mall?)

[waterbear]

Oh No!!!! You guys are gonna get people thinking they need to move here! We are already the densest state in the union...Think Sopranos and "Fugeddaboudit" and Joe Piscapo...and the Turnpike..
Carl, are you implying that you tink people from New Joisey talk funny?;) (I will resist taking the very easy cheap shot you left me about 'densest state in the union', but is it tempting since I AM from there! ROFL!)
As far as the Turnpike goes:eek:, take a spin on I-95 in Miami or the vast parking lot known as the L.A. freeway (other places I have lived) or try driving through Atlanta during rush hour and you might find it ain't that bad!;)

Anyone from NJ will understand the love/hate relationship people from there have for the state. It truely is beatuiful and blighted at the same time. I still have kin there and go back every year or two for the holidays.

[CarlD]

Yes, it's been Short Hills Mall since we moved up here 14 years ago. Despite having grown up nearby, when we moved back up from Virginia, it was like moving to a new country--completely different. We moved back up here for my wife's career and to be halfway between our ageing parents.

Anybody who thinks things move slower Down South never stood in line at a Home Depot or Staples up here! And, until recently, the DMV was the WORST in the nation--every transaction (License renewal, registration renewal) took 1 hour on a good day. So if you had to renew your license, the registration for 2 cars, and (in my case) 1 motorcycle, that was 4 transactions, 4 hours. No joke, it was THAT bad--and corrupt to boot--it was faster to get a license by bribing someone inside to make you one...a whole bunch of people went to jail for that.

Amazingly, the efforts to fix it and clean it up have worked. I renewed a car the other day at the local MV office and was in and out in 10 minutes, despite the place being full.

Actually, the REAL reason NJ has a bad rep is that it's to the west of NYC, and there's a river between them. So New Yorkers only ventured across with trepidation (Until I was 12 I think I went to NJ maybe 3 times). Between the swamps and the decaying Hudson River towns (all of which are having a HUGE renaissance), NJ became the punchline of a lot of hip, NY comedians' jokes. "You from Jersey? What exit?" These days, Tony Soprano doesn't help! (tho the Tick-Tock Diner is a VERY real place). And, no, Jimmy Hoffa isn't really buried under the West goal post at Giant Stadium--at least we think he isn't....

Plus there is our VERY interesting version of politics here. Still, it is one little dynamo of a state, and having grown up and gone to college in Upstate New York, I find NJ far preferable.

But there are STILL some things here you just couldn't make up! Like they put the sign for an exit on the FAR side of the exit so that when you finally SEE it, you've missed it! And this is the only state without self-serve gas--an attendant (who tops your tank, spill gas down the fender, and keeps your change without permission) is considered "safer" somehow.
We probably have more diners per capita than any other state, too. And here's a little secret: Good NJ pizza is just as good as good NY pizza--sometimes better!

[Poconos]

I can't resist throwing my 2 cents at NJ. Lived across the river from Northeast Philly most of my life and finally left for the sticks of Northeast PA 10 years ago after working here for 5 years before that. Real Estate taxes less that half, auto insurance the same and I have the right to protect myself and have a lot more property. I'm glad to hear the DMV has gotten its act together...but here I do business online. I used to dread the lines at the state inspection stations too. And Carl, you left out one comment...about the gas station attendant pumping gas with a smoke in his mouth. Unless it has changed I think Oregon or some state out there was the other one that didn't allow pumping your own. PA isn't perfect but I sure like it better here and could kick myself for not leaving the 'Garden State' sooner.
The vent felt good.
Al

[CarlD]

Don't see so many anymore smoking and pumping gas--guess that proves Darwin was right!!!:D

(can you say KA-BOOM!!!??)

[waterbear]

And here's a little secret: Good NJ pizza is just as good as good NY pizza--sometimes better!
TreeTop Tavern Pizza. It was the best in the world. Wonder if it's still there?