Problem removing algae completely

I have been maintaining my own pool for 8 years and had my share of ups and downs, but this time I am stumped! (After reading a little on this forum, I think I have just been lucky in the past.) My current problem is that I cannot get a FC reading no matter how much chlorine I add! And the algae bloom that started last week, has gotten better, but will not go away completely! I get my testing done at local pool store, and foolishly have been following their advice. (Which seems to change depending on which clerk I get!) So I am DONE listening to them! Anyways, here are my latest test results:
FAC 0; TAC 0; CH 370; CYA 100; TA 120; pH 7.4; TDS 1200; Pho 300
Temp 85-90 (hey, I am in FL and it's JULY!)

Pool Specs: 12,600 gallons
Surface: Marcite
Filter: Hayward De
2 waterfall returns
Screened with minimal plants on porch


This afternoon i added 2.5 gallons of LC from pool store (they fill the jugs from their daily shipment)
after backwashing filter and filling pool for 45-60 minutes fresh water.
Then it rained quite a bit in the evening. YES!
Quit using 3" tablets last week.
So, what do I do next?
Thanks!

Hi Nancy,
Do you know what percent sodium hypochlorite your pool store chlorine is? If we know that, we can determine the quantity you need to add to shock your pool to the right level.

Your CYA level may not really be 100. 100 is the highest that the test can differentiate, so it actually may be much higher than that. You basically have two options:

1. Do a partial drain and refill and try and lower your CYA to a more manageable level. (Do NOT totally drain the pool, however.)

OR

2. Run higher than normal chlorine levels to compensate for the high CYA. (See the Best Guess Table in my signature below for more about that.)

You'll need a good test kit so you don't have to depend on the pool store. Plus, you need to be testing every day and several times a day when you are having problems. You're not going to want to keep making that trip to the pool store. The one we recommend is the Taylor K-2006 or 2006C (same kit, larger bottle of some reagents). If you buy it through the Amazon link in my signature, the Pool Forum makes a little money on the sale which helps us keep this form online. Only buy if the seller is Amato Industries, however. Some other sellers are substituting the K-2005 which you do NOT want. If Amato isn't listed, wait a day or two and try again. They seem to restock pretty quickly when they sell out.

Reply back with info about the LC and also which option you like and somebody here can help you go from there.

Welcome to the Pool Forum!

Thank you for your quick response!
Store chlorine is 10.5%
I am willing to do both, if it resolves the situation quicker.
I will get it tested at the pool store today when I go get the LC that you tell me I need.
I will also purchase your suggested test kit today from Amazon.
Thanks again,
Nancy

You won't do both. Pick one or the other.

For now, add 3 gallons of the 10.5% chlorine. That should take your chlorine up to 25. We want you to test as many times per day as you can, and each time add enough chlorine to get back to 25ppm. Glad you ordered the kit. Good decision. But, for now, go to Walmart, or even to the pool store and buy a cheap OTO/Phenol Red kit (yellow and red drops.) It isn't ideal, but is reliable and will do until you get your kit. It will only test chlorine levels to 5ppm but you can force it to go higher by using a dilution method described here: Testing Without a Good Kit

Only use the LC for now. No more pucks, no dichlor shock powder, no cal-hypo. Just LC.

Let us know which option from my earlier post you pick so we can best advise you.

I added the 3 gal. LC
As far as picking one or the other of the options, am I right in thinking that it is in my best interest (financial and time) to do a partial drain and refill to reduce the CYA level? Otherwise, I will ALWAYS have to keep an extremely high FC level.
Right? I do have a cheap kit to use in the meantime to check the chlorine level until my new one comes in. (I mostly use it for my well) I will be testing the chlorine level using the method you mentioned.
What's next?
Thanks!

Either way would work. Except -- I now see mention of a well. Would you be refilling from a well? Sometimes that creates another whole host of problems as many wells have metals in them.

Yes, you would have to keep FC higher if you run a high CYA pool, but overall, it might not be that much more bleach because high CYA/ high FC pools don't have to have LC added as often. So, it kind of balances out. Sometimes, CYA goes away over the winter, sometimes it doesn't. You might decide not to do the partial drain and refill and just see what happens with this pool over the winter.

Either way is fine. Just a matter of preference.

If you decide not to partially drain, then continue testing and adding LC to get back to 25ppm as many times per day as you can. You'll continue to do this until you can go from sundown one evening til within 2 hours of sunup the next morning without losing more than 1ppm of cl. At that point, keep the cl high for one additional day for added insurance and then you can let it drift down and then keep it between 8-15 ALL the time so you won't get another algae bloom.

If you decide to go ahead and partially drain, go ahead. No sense wasting LC and thus money that you'll then be throwing out. Once you refill, you'll test the CYA to see where you are with it then, and follow the Best Guess table for shock levels. And, as in the previous paragraph I wrote, you'll test as frequently as you can and add LC to get back to shock level until you can pass the overnight test.

Hope this helps.

I have room for more fresh water in the pool, so I will at least do that, and retest to see where my levels are.
After reading your last post, I think I might just wait it out and see what happens over the winter.
Yes, I fill from a well. But I use the water after its been filtered. (Drinkable) I tried one time using it from the faucet prior to it going thru the charcoal and there was too much iron coming out. (That was a LONG time ago)
Guess it's just gonna take some time, now that I have a plan.
Should I do anything about the TA being so high?
Thanks!

A TA of 120 is not high.

Ok, won't worry about the TA then.
Oh, forgot to ask.... what about running the pump. Just the usual 7-8 hours a day? or longer? And backwashing? Just when it goes up 8-10 lbs?
Thanks,
Nancy

Run the pump 24/7 anytime you are trying to clear water. Backwash when the pressure rises 5-10 psi over clean filter pressure.

Update:
The algae is gone.
The chlorine reading stayed up overnight and has stayed up so far today (it's 3:15pm now)
Filter pressure is normal.
So I will keep testing to make sure it doesn't drop more than 1ppm from the 25ppm through today/tonight and then starting tomorrow I will let it drift down and keep it between 8-15 ALL the time.
I am also going to keep an eye on the CYA, so I can adjust the FC accordingly, per the "Best Guess" Chart. (We get frequent heavy rains, so hopefully that will naturally bring it down) What should my target reading be? Just curious.
All this testing sure will be easier when the new kit arrives!
Thanks for all your help!
Nancy

Woo Hoo!! Congrats and good job. Sounds like everything is falling into place. The CYA level that most people target is 40-50. Then, after some time, if you find that you are having trouble keeping chlorine in your pool especially on hot, sunny days, you can always bump it up some. Living in Florida, you may find that necessary but I would try 40-50 first.