Ph Rise, little cloudiness

Jump to latest Follow Reply
M

Mr. Coconut

0
Mar 12, 2011
5
I have two separate issues that I'd like to resolve. The first is the issue of the consistent rise in Ph I see, especially when adding chlorine. I use 12% liquid bleach. First, the numbers:

24,000 gallon in-ground plaster pool
FC: 6.0
CC: 0.0
TC: 6.0
PH: 7.8
TA: 130*
CH: 245
CYA: 50*
TDS: 500 (measured this weekend, pool was refilled about 6 weeks ago for a patch)
Water temperature is about 84 right now (not heated, just in South Florida)
*see notes below.

First question: when I add bleach to shock -- usually about one and a half bucket, i.e. 3.75 gallons of 12.5% bleach -- I notice a very steep rise in Ph, driving it from 7.5 up easily above 8.2 to where I cannot properly measure it anymore. I know that as the chlorine is consumed, the Ph is supposed to drop again, but that's not what I am seeing. I shocked last night -- pump running all night long -- and this morning, FC is down to about 6 but Ph was still above 8.2. I started at 7.5 before I shocked. Why is this? I though that liquid bleach was supposed to be largely Ph neutral (Ph rises at first and then comes back down as chlorine is consumed). On the whole, I end up using quite a bit of Muriatic Acid to correct for this every time I shock and I'm wondering what it means.

Second question: even though I shocked last night with 3.75 gallons of bleach, I noticed significant algae still this morning. I brushed right after I noticed them -- didn't have time last night -- but I'm surprised. In addition, I had significant cloudiness this morning. Should I be shocking even harder? I do still have about 6.0ppm of free chlorine, which should be enough, but apparently is not. Any suggestions?

Notes: The alkalinity and CYA readings are tricky. As for CYA, I've had one store measure it at 100, another at 50, and my own test kit suggests 30. Not sure what to believe. I can say that when I refilled the pool, I added enough stabilizer to bring it to about 60. Alkalinity is similar story: one store has it at 160, another at 130, and I have two test kits which give me 120 and 150 respectively. The 150 reading comes from the more elaborate Leslie's test kit (recommended here) and the other reading from an OTO test kit. In any case, no agreement on either the CYA or Alkalinity. Stores also tested phosphates at about 200, but my understanding is that they should not matter at all with proper shocking and maintenance. I only use Liquid chlorine, no floating pucks: they gave me the worst CYA problem last year, so I'm trying to do without altogether.
 
If pool calculator is right, you added 20 ppm FC. Overnight it dropped to 6. You're not done shocking. Not by a long shot. It's not a one-time thing, it may take days or weeks. And not knowing the actual CYA makes it pretty hard to know if you're even getting enough FC to kill the algae faster than it can reproduce. If you're not, all the bleach you've added has been for nothing. If, say, your CYA was 60, shock level is 18. If you bumped it to 20, it won't take long to drop back to 18. It's essential to know CYA. And to keep the FC up up up by additions every hour or two if necessary.

With your TA where it is, pH is going to keep rising. And when it goes alkaline, the calcium will make it look cloudy.

I would ignore pH for now and concentrate on shocking. Perfect pH and TA mean nothing if the pool is green and thick enough to walk on.
 
As Richard said, you ain't done shocking! You need to read Pool School on proper shocking. You need good test numbers in order to know what your shock level should be and you need to keep it at shock level (adding chlorine as often as every hour) until you pass the OCLT (Overnight Chlorine Loss Test).

If you have the Leslies equivilent of the Taylor K-2006 then you should run your own test and trust your results. If you have the K-2005 equivilent then you need to buy a FAS-DPD kit to suppliment it.
 
The PH test doesn't work correctly when the FC level is very high (over 15). It will read higher than actual in that situation. As Richard320 said, ignore PH while FC is high.

The most reliable CYA test is the one where you add liquid to a view tube until the black dot at the bottom of the tube can not longer be seen. Doing the test is a little confusing/speculative, but it is still the best available test and far more reliable than test strips.
 
Also when doing the cya test you can do it more than once at a time. After you pour into the tube to with the black dot, pour it back in the bottle you just poured it from and do it again. Once you feel you get consistent results this way use this as your number. The CYA test is one of the hardest, but most important test to do. Knowing when the black dot is gone is different to everyone and they will see it differently as well.
 
Thank you all for your advice. I will follow the guidelines for continuous shocking until it's perfectly clear. As I said, the issue with the CYA is tricky since I understand that it affects how much FC should be in the pool. Like I said, I have three different readings, two from stores and one myself (did it twice, came out about the same) and those readings are not at all in line. The test I used here is the one with the black dot and gives me about 30, which I know cannot be right since I dumped enough stabilizer in there to give me about 60, which is what I aimed for (I recall it being around 10 lbs of stabilizer). Not sure what to make of those results. I suppose that keeping the PH under control will eventually bring the alkalinity down without too much further intervention.

One last question, though: if I shock until clear and until I have less that 1ppm worth of FC loss overnight, will it not take a good long time for the pool to be safe for entry for my kids (3 y/o)?

edit: also, in so far as the alkalinity is concerned, I've already brought it down from 230 which is how it comes out of my well. Having the alkalinity even that high didn't appear to result in cloudiness in and of itself. In fact, it was perfectly clear until it got warmer around here -- except for one incident with cal hypo, which I will not be using again.
 
With CYA around 30-60 you should lose somewhere in the range of 50% of your FC level each sunny day, more if CYA is at the low end of that range, so one full sunny day should be more than enough to get the FC level down to something reasonable.

Your levels are still high enough to put you at risk for calcium clouding, even if you never had it while your TA level was higher still. I don't think it is at all likely, but don't completely dismiss it as a possibility.
 
I appreciate your insight. I did as outlined in the pool school -- keeping FC at shock level for as long as warranted -- and now have reached the point where the water is crystal clear. I'll see how much FC we lose overnight, but I have high hopes. I will diligently work towards a lower TA (aiming for 80-ish) and keep on top of the FC levels. Hopefully, that will result in less need for shocking. That would be nice: my kids are in the pool every day from March to December. I suppose my only difficulty now is in determining what the actual level of CYA is. Still not certain how to resolve that issue; I brought in samples again to two stores, just to see if they could agree for once, but no: 50 and 100. I'm still seeing 30-40 when I do it myself, while the pool calculator tells me it should be around 50-60 based on the amount of stabilizer I added. I'll probably have to settle on fifty as the most likely candidate.

One last question: for the TA readings, I also get competing scores. The stores tell me either 160 or 130 and doing it myself I get either 120 or 150. The alkalinity test included in the simpler OTO test-kit tells me 150 and the test included in the FAS-DPD gives me 120. I know that the FAS-DPD is much better for chlorine, but what is the difference in testing for alkalinity between the red/green and the blue/clear tests? Is one inherently more accurate than the other?
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply