7.2 vs >8.2 Grrrrrrrrrrr

[Infidel]

Thanks for all the info. Here's some background:

Alk 120 (consistent with reading 2 wks ago)
Ca 350 (consistent with reading 2 wks ago)
CYA ~100+ from reading tonight, has been reading 72-80 last 2 wks
pH 7.6 OTO / <7 Taylor (as of 2am Texas time)

Cl is being read from the Taylor at 1:5, color is usually between the 3 and 5.
I'll grab a pH meter from work tomorrow and start checking the "real" pH and see what method is accurate. I use the K-2005 kit from Taylor.

Are you sure 6-8 ppm is suitable for lime green pool with CYA ~80? WIth regards to consistent concentration, I'm unable to distinguish between the 3 and 5 (15-25 ppm) on the color comparator, so if it's yoyoing, it's doing it between 15-25, which should be sufficient to keep things killed, even at the low point in the cycle, correct?

The pool is looking less green since adding acid 4-5 hrs ago. The low pH should be increasing the %hypochlorus according to Duraleigh's excerpt, which appears to be occurring. So, algae in spite of high Cl, may indicate pH is elevated and the active Cl isn't present in great enough quantities it sounds like.

Are phosphate / nitrate commonly performed by pool stores?

[brent.roberts]

I've seen it posted here a number of times that the best range for PH when fighting algae is 7.2 to 7.2

The above explanation about ion levels shows why. So I think I'b be shooting
to get the PH to 7.2

To really get the kill going well, tonight, as soon as the sun is off the pool, dose it up to your shock level. Run the pump to circulate and re-test in an hour or so. If you see a big drop, dose it again, and keep doing that till you can't stay awake. This will cut the yo-yo out.

If the majority of the CL is consumed in the first couple hours after adding, the the algae can go right on growing again throughout a lot of the night. So check it every hour or so tonight.

Keep track of what it does and let us know.

[duraleigh]

I am watching this thread devolve (yes, that's the word I meant) into issues that I think are peripheral to the problem. Chlorine kills algae

If you still have algae in your pool, you have not brought your chlorine levels high enougn, long enough to get rid of it.

The solution is to bring your Cl level up to about 30-35ppm in the evening and then test your Cl the next AM. Whatever drop has occurred is the result of killing organisms. Bring your Cl right back up to that 30-35 level immediately. Hold your Cl at that level until your pool is clear and then let it drift back down into a maintenance range of around 5-10ppm.

If this fails, (and I've yet to see it fail on this forum) then I think you could safely assume you have another issue. You cannot tiptoe up to your algae problem....you must kick it straight in the butt with chlorine and kick it long enough to get the desired effect....a clear pool.

PS - If it's not clear, I am in complete agreement with Brent, I just like to use big letters more than he does.

[Infidel]

I agree with both of you.

This morning, Mr. Taylor says my Cl is 20ppm and my pH is 7.0 or a tad less. No retreat on the algae front, bombs away.

edit: just added 5ppm Cl to the pool. My pool is shaded most of the day, forecast calls for rain for the next 3 days here anyways, so no worries on waiting for the sun to be off of it.

Anyone feel it's necessary bring the pH up a bit? Or is a tad low during an algae assault preferred?

[Infidel]

8hrs later, still no change in algae, Cl maintaining at 25-30+ppm, pH ~7 per the Taylor kit. There appears to be no consumption of Cl at this point, and no reduction in algae.

Is it possible the breakpoint has not been reached at these levels, or that the Cl is being rendered innefective for some other reason?

Didn't go to work today, too tired from being up at 4 am testing my pool no pH meter. Did try to take a water sample to a pool store, far underestimated the quantity they'd need. They also said they'd need my surface area and volume. No chemical parameter I've ever seen is dependent on those things, only the amounts of chemicals a store wants to sell you. Why can't they just give me numbers. How much grief can I expect when I tell them I'm just confirming my home test kit numbers.

[duraleigh]

I would add a massive dose (1,000,000ppm) of POP....Pool owner patience. Clearing an algae issue may happen overnight but, more likely, will take a few days (from the time you reached breakpoint.....8 hours ago)

The important thing to remember is .....stay the course. Don't let your Cl drift down until your water is clear. You're running your pump 24/7 and backwashing as necessary, aren't you?

[waterbear]

I've seen it posted here a number of times that the best range for PH when fighting algae is 7.2 to 7.2
actually, If you are fighting algae a pH of about 7.8 is beneficial because you will favor the formation of monochloramine, which is a very good algae killer. It is short lived, however so you will have a big chlorine demand.
The above explanation about ion levels shows why. So I think I'b be shooting
to get the PH to 7.2

To really get the kill going well, tonight, as soon as the sun is off the pool, dose it up to your shock level. Run the pump to circulate and re-test in an hour or so. If you see a big drop, dose it again, and keep doing that till you can't stay awake. This will cut the yo-yo out.

If the majority of the CL is consumed in the first couple hours after adding, the the algae can go right on growing again throughout a lot of the night. So check it every hour or so tonight.

Keep track of what it does and let us know.

Hope this is helpful! Also, I would double check your CYA levels. the test is the most subjective and it is possible that they are higher than you think they are. Your own testing hints to that! In that case you have probably not brought your pool up to a true shock level and kept it there long enough to kill the algae!

[Infidel]

I suspect the CYA levels are higher then I thought, as the last test indicated. Since my Cl readings are so variable, I'm sticking to a schedule of adding 12.5ppm Cl every 12 hours (8am, 8pm). This should hopefully maintain at shock level long enough.

The pump is running 24/7, not backwashing though due to the pressure in the filter tank not being elevated. Pool Co. out to give me a quote on replaster yesterday indicated that my sand filter may need cleaning if I've got lots of algae that is difficult to remove. Any truth to that?

[duraleigh]

Backwashing cleans your filter and sand....that's all you need. You may backwash anytime you like but I always look for a pressure rise first.

That 12.5ppm worries me a bit. How do you know that? It sounds more like you are putting in 12.5% Cl which may or not relate to ppm. How big is this pool (gallons)? If it's 10k, I understand. If it's not, you need to recalculate.

[brent.roberts]

I want to encourage you to check and top up the chlorine more frequently than every 12 hours.

Here's what can happen.

At 7:00 PM you top you your chlorine to say 20ppm. If there is a lot of algae
in the pool it can be down to 8 or 10 PPM in 2 hours. After 4 hours the level is so low that it starts growing and reproducing again. By the time you get up the next morning at 7:00 AM to top it off, you are back to the same pea soup you had when you went to bed.

Now you top up at 7:00 AM and you have the whole day's sunlight to kick the h*** out of the chlorine along with the algae basking in the sun and reproducing.

Try to shorten the cycle. Initially topping up every couple hours could be quite important. As the algae concentrations go down, the yo-yo of your chlorine levels will slow down and you can relax the schedule a bit, but you've got to break the back of the chlorine.

Do you have a reliable CYA measurement yet ??