Adjust TA when chlorine very, very high?

[dawndenise]

I'm in the midst of a battle with what appears to be that hard-to-kill algae. I've been running my FC in the mid-20's, gone to 30 and just now added enough bleach to go to 35 . This is kinda scary.

My TA had been solid at 80 all summer until a test on 9/13 when it dropped to 60 for unknown reasons. Added 4# baking soda, tested out at 80.

Then the what-I'm-assuming-is-algae happened. In the midst of battle, my weekly test for TA was 60 again. Added just 1# of baking soda on Monday and Tuesday's tests showed no change in TA. Added 2 more pounds of baking soda yesterday and today there's still no change, still reads 60, maybe even 50 because the color changes are different at high chlorine levels.

Could my high chlorine levels be influencing my recent TA levels? Should I continue to add baking soda? Don't want to eventually have normal CL and find out I have too high TA.

TIA for any advice and input.

[chem geek]

Sandy,

Your TA will yo-yo along with pH, but even going from a pH of 8.0 to 7.0 by adding acid (or using Tri-Chlor) would only cause the TA to go from 80 to 67 if your CYA were 30. If your CYA were 100, then that TA would go from 80 to 61. So we can probably eliminate that TA/pH relationship as the main source of your drop in TA, especially if you measured the TA of 80 and 60 at the same pH level (did you?).

So that leaves carbon dioxide outgassing, but if that were occurring then you should be seeing a significant rise in pH that you have to counteract by adding lots of acid. Is this what you are seeing?

As for the TA test and interference from chlorine, you do add Sodium Thiosulfate drops as part of the TA test and this is intended to breakdown the chlorine because a high chlorine level will make the test go from blue to yellow (which is much harder to see) instead of green to red. To avoid this (if you see blue/yellow instead of green/red), just add more drops (say 4, instead of 2) of thiosulfate to your sample before titrating.

Last, but not least, what is your CYA level? The shock level you will need to kill the hard-to-kill algae (if that's what you have) is dependent on your CYA level.

P.S. When you add lots of chlorine, the pH will increase a lot as will your TA. As the chlorine gets used up (or if you add acid), then the pH and TA will get lowered pretty much back to where they were.

P.P.S. If you really do have this hard-to-kill presumed yellow/mustard algae, then it may take a chlorine level of at least what is found in the column "1.00" in this chart. If you have high CYA, this could mean exceptionally high levels of chlorine to kill this stuff.

Richard

[dawndenise]

Richard...thank you for your reply. Your chart, in another thread, is what's prepared me for the chlorine levels I'm now using - but I'll get to that.

My drop in TA on 9/13 was measured at a ph of 7.8, my previous "normal" of 80 throughout the summer was at a pH of 7.5. Just prior to the 9/13 tests, actuallly on 9/7, I ran a pH test with the Wally World HTH kit and also with the Taylor reagent from Ben's kit. With the same water sample, the HTH measured 7.5, as it had been for nearly the entire summer but the Taylor measured 8.0, maybe higher. The HTH kit HAD measured higher pH values accurately (I'm assuming) in early summer when I first tested my new pool's water.

Since then (9/7), I've been adding small amounts of muriatic acid every few days, if not almost daily and have yet to see a nice solid 7.5, as this summer. I recorded today's test at 7.5 (almost) but with no MA additions today, I'll bet tomorrow it'll be at least 7.8.

Looking back, maybe all my TA drop is from the additions of muriatic acid. After running such a stable pH all summer, I haven't had to remember that concept because I added so little MA all summer and my TA stayed right at 80.

Outgassing...I do have a waterfall that, previous to this algae, had been on 12 hours a day. I had absolutely no problems with stable pH during the summer. The only change I made in early September was to run the pump (and waterfall) for the majority of time in the daylight, rather than overnight and drop the time to 10 hours. Right now the waterfall is off to make sure all water is running through the filter.

My CYA measured 50 or slightly higher on Monday's test. Like most new pool owners, I struggle with consistency - at times, I've measured it at 40. I did recheck and can say that I've added 10# of CYA since the pool was finished in June. With no draining or backwashing (cartridge filter) a CYA of 50-60 is probably correct.

Your chart, comments, and the experiences of other forum members have helped a great deal, as I would have never expected to have to go over 20 FC to clear up my pool. Not that it's clear....yet. Going to 35 or a little higher MAY have been just the ticket; I'll know more in the morning when the light is better. Having never had algae and having never had a pool before, I still can't say for sure that algae is what this is...but it's my working theory.

IF both pH and TA should return to lower levels when the chlorine returns to more normal levels, what do I do in the meantime? Do I just keep trying to keep pH and TA somewhat in balance while my FC is so high?

[chem geek]

IF both pH and TA should return to lower levels when the chlorine returns to more normal levels, what do I do in the meantime? Do I just keep trying to keep pH and TA somewhat in balance while my FC is so high?

A higher pH is actually beneficial to killing the algae (there is less disinfecting chlorine, but the algae cells take it in more at the higher pH), though it shouldn't go above 8.0 or your pH test kit limit. So yes, you may need to add some acid during this high chlorine period and you'll have to keep the chlorine high so will have to continue to add chlorine (let us know the chlorine usage, especially overnight, as this will be an indicator of how much is getting used to kill the algae). You shouldn't need to keep adding acid once you've got the pH where you want it.

After the algae is killed and the chlorine maintains its level overnight, then you will let the chlorine level drop (get broken down from sunlight during the day) and you'll need to add base (Borax) during this process, especially if your pH gets down to 7.0 or your pH test kit limit.

It is not terrible if you just ignore the above advice and just keep the chlorine high with whatever its high pH is, but it might take even more chlorine to kill this algae under such conditions.

I'm a bit disturbed by your inconsistent pH readings. It's difficult to accurately measure the pH when there is a lot of chlorine (> 10 ppm) since the indicator will turn dark purple above a pH of 6.6 and this can be misinterpreted as a dark red so that you think the pH is higher than it really is. You could add some drops (2-4 drops) of sodium thiosulfate (the same stuff you add at the start of the TA test) and then test the pH, but the thiosulfate breakdown of chlorine is an alkaline process so will generate a false high pH reading (but you can just subtract about 0.1 pH from your measured pH for every 2 drops of thiosulfate as an approximation). If you happen to have "acid demand" drops, then you can try adding these after you take a reading to see which direction the color goes. Try the "acid demand" drops and see if the colors change from the high pH red to the low pH yellow.

Richard

[dawndenise]

Hi Richard,

Unfortunately, no demand drops to try.

This situation is both aggravating and intriguing. Up until yesterday, my FC readings weren't dropping any more than one would expect from sunlight; no big, big "chlorine demand," yet my pool water was a mess. So I decided to keep upping the chlorine just based on the look of my pool.

That trend of really no chlorine demand and 0 CCs existed until yesterday afternoon. In the AM, my FC was 30.5 with no CCs. Per another post of mine, I also turned my SWCG back on - 30% level - pump on 24/7. Still, because my pool really hadn't changed in appearance from the day before, I added enough bleach (182 oz) to up my chlorine by 5. Expecting about 36 at 2PM, instead I got a mere 31.0 and minimal CCs.

I added another 182 oz of bleach. Expecting something in the neighborhood of 36 at 7:30PM, instead I had only 24.5 with CCs at less than .5. This was the very first time I had seen a big chlorine demand. Sure, there was sun on the pool, but that had been the case the last few days as well and no significant drop in chlorine like this. By 7:30, I had also been able to smell some chlorine in the air. I also thought I saw the beginnings of some blue and some clearing coming back to the pool, but it was getting dark.

I upped the SWCG to 50% and also added 237 oz of bleach to take my readings back up by 12.5, to the over-35 range for overnight (take THAT, you algae! ).

This AM, my FC is at 38.0 with 0 CCs, as if things stayed pretty stable overnight. Pool is definitely clearer , as I can just about see the Phillips head screws in the drain covers.

I'm going to keep the chlorine levels up until my pool looks crystal clear everywhere like it did 2 weeks ago. I'm thinking of staying in the 35-ish area, which also coincides with your chart!

pH was at least 8.2 this AM, TA 50. Had already put in MA before I came to read posts so may actually be lowering my pH too much. Will try the sodium thiosulfate and see how much I screwed up.

[dawndenise]

The saga continues.

Chlorine only dropped from 38 yesterday morning to 35 by 2PM. pH measured about 7.6-7.7 w/sodium thiosulfate drops first. Added 91 oz (1/2 jug) bleach to raise chlorine to about 37.5.

By 6:30 last night, pool continuing to look clearer in the shallow end, still hazy with greenish/yellowish tinge in the deep. Had high winds all day so a lot of debris came in - just what I needed . At 6:30, chlorine was 32 and CC less than .5. Added 2 jugs (364 oz) of bleach to raise CL level by 10 to about 42 for the overnight.

This AM, pool 99% clear in the shallowest sections and clear on edges of the deep. Sun came on the pool and the middle sections and deep end still a bit hazy with that light greenish/yellow cast. FC was 43.5, CC less than .5 and my pH w/4 drops sodium thiosulfate, was over 8. First time I was actually seeing a purplish color in the tube. TA fell and is now at 40.

Added about half gallon of muriatic acid. Will let circulate for awhile and then add 2# baking soda. Won't put me where I want to be, but I can't help but think that my pool can't take being out of balance with super high chlorine, extra low TA and high pH for that much longer. This is such a different situation that what I had all summer.

As long as I'm seeing that light greenish/yellowish cast, I still need to keep up my CL levels, right? It's just hard to believe that anything could be growing in there at those levels.

Does anyone know if an algaecide is of any use as a preventive measure against this stuff?

[chem geek]

Patience, patience, patience. Yes, it can take some time to kill off a lot of algae. At least it's getting better, so stick with it. With your CYA of 50-60, I wouldn't go above the FC level of 40 since that should be enough to zap even this hearty algae, and it sounds like it is. At this point, just wait this stuff out keeping the FC at the high level. Don't worry about adding any more acid at this point -- your dropping TA could mean that your pH isn't really as high as you think (due to high chlorine and extra thiosulfate drops) and when the chlorine level drops back down (after you've conquered your algae problem), the pH will drop anyway. Just add the baking soda to bring up the TA again (I wonder if the algae is consuming the carbonate???).

And hang in there -- you are on the right track! Oh yes, with this much junk you are killing in your pool, you will probably have a lot to vacuum out and/or to clean out of your filter. You might check your pressure to make sure you haven't caked your filter with this stuff.

As for algaecide, some people have reported success using 60% polyquat algaecide, but this is best done BEFORE the algae starts -- as a preventative -- so would be something you would add before August each season since that is when people first start reporting this hard-to-kill yellow/mustard algae (which sounds like what you might have). Perhaps keeping higher chlorine levels would also prevent this stuff, but we don't know enough yet of how high that would have to be (i.e. is the high end of Ben's chart good enough to prevent this stuff???).

Richard

[dawndenise]

Richard,

Thanks for the encouragement. Once I decided to go with the theory that this was algae, I really thought I'd be cleared up by now. Dump in a bunch of bleach, filter on 24/7 and wait 24-48 hours and - presto! - a clear pool, right?

The odd thing is that I truly thought my CL levels were on the high side prior to this. I guess a lot of organics can overwhelm even a relatively high CL.

Also had another thought on how this happened - a hose. We used a couple of hoses strung together to siphon out our pool during construction when it was pretty grungy and we were hosts to a number of toads (we relocated them prior to draining). We were also concerned about mosquitos breeding in the standing water. I don't remember exactly which hose was used for discharge of the grungy water, but I know certain hoses we use a lot, were not. Normally, those known-clean hoses are the hoses I use to top off the pool.

Just 3-4 days prior to the first white-ish haze, we cleaned the filter and I had to connect 2 hoses to reach the area. If the second hose I connected happened to be a previous discharge hose, well, then I could have introduced heaven-only-knows-what directly into my filter . That combined with the organic overload might have triggered this whole thing.

I'll be trashing all suspect hoses.

[dawndenise]

Final update: Pool cleared and came back to its nice color on Day 9, although a bit of whitish haze around the drain persisted. Kept CL levels up for another day and by Day 11 began to let the pool come down to its normal levels.

This morning's readings (would be Day 13, if still counting) are FC 15.5, CC 0, pH 7.5+, TA 70. SWG at 35%, salt level 4000-4100 (due to mega bleach additions), pump back on 10hrs.

Things learned:

1.) Shock the pool to whatever level it takes at the first sign something is not quite right with your pool - trust your instincts.

2.) Keep a good supply of testing reagents on hand. Testing FC at 30-48 3x/day can use up a whole lot of drops!!!

3.) Don't use scummy hoses to top off your pool or clean your cartridge filter.

4.) Keep one shock level of bleach, or cal hypo, or whatever, on hand so you can take action on a problem immediately.

5.) Seriously think about adding some polyquat 60 in August or early September.

The PS234S was indispensible! Can't even imagine how I could have managed this outbreak with the shot glass method (nothing against the method, but doing a reading with 1 part pool water and 5-9 parts distilled water would have been just too inaccurate).

Thank you Richard for your advice and encouragement. Thanks to the others who posted on other threads/forums where I posted other questions before I knew what I was dealing with.

Missed probably 1-2 days of swimming during this, as the temps have been cooler. Pool was at 68 degrees this AM but we have 3 days forecasted to be in the 90's with overnight lows in the 60's, so may be able to squeeze in a few more dips and laps. Should help to lower that CL reading just a bit, too.

[chem geek]

Sandy,

That's great news and I'm so glad that you conquered this algae. Your tips of what you learned are also excellent.

Another alternative or even in addition to using the Polyquat 60 in August each summer as a preventative for algae would be to have 50 ppm Borates (from Borax) in your pool (at all times). We don't know yet if the Borates will prevent this particular hard-to-kill algae, but I suspect that it will be at least as good as Polyquat 60 for preventing algae plus has additional benefits of greater pH buffering (stability) and lower chlorine consumption. Apparently, Evan's got me "hooked on Borax" and I plan to add both salt (1000 ppm just for the "feel") and Borax (50 ppm) to my pool starting next spring.

Richard