chlorine/algae problem

First time posting.. Any suggestions would be greatly appreciated !!

16x32 in-ground pool
approx 23,000 gallons. deep end 8ft low end 4ft
sand filter
1.5 hp pump hayward

I believe the pool was closed slightly green.
current readings:
TC 3.7
FC 0
PH 7.2
TA 80
CH 200
Stabilizer 60

When we took the cover off about three weeks ago the water was dark green. We used about 5 bags of powdered shock from Sams Club and it had little affect. Over the next couple of days we continued to shock the pool with no noticeable difference. we have never been able to get a FC reading higher then .5. We've tested the water at home using test strips (sorry about that) and have brought the water to a local pool place as well as Leslie pools. On the advice of Leslie Pools we added Green out and when that didn't work Pool First Aid with again no change.
I discovered this forum and switched from powdered shock to liquid chlorine, first using 6% and then purchasing from the pool place 12.5%.
The first night I added 6 jugs (96oz each) of 6% and had no FC reading in the morning
the second night I added the 5 gallon jug of 12.5% and as of this morning still no FC reading on our test strip.

The water is no longer dark green but cloudy with a green tinge, you can see the bottom of the pool in the low end but not in the deep end.
How much liquid chlorine should I add at one time?

Thanks!!

Hi and welcome!

Any idea what the CYA reading was at closing last fall? Some pools open with HUGE chlorine demands. You think your FC is never gonna hold and then finally it does. With a CYA of 60, you need to be shocking up to 20ppm and try and hold it there. In a 23K pool, each 5 gallon jug of 12.5% liquid chlorine will add about 27ppm of chlorine. That is actually a little higher than you want but since it is not likely to stay that high for long with your huge chlorine demand, it probably won't hurt anything. (Is this a vinyl or gunite pool or ??) If it's vinyl, you might want to only use 4 gallons at a time. (Each gallon will add a little more than 5ppm.) Keep hammering it hard with the liquid chlorine.

Your teststrips are most likely getting bleached out at the high cl levels. You really need to get a good kit. See the Amazon link in my signature below to pick up a Taylor K-2006 or 2006C kit which is the one we recommend. Only buy if the seller is Amato Industries. Other sellers may substitute the K-2005 which you do NOT want. With a CYA of 60, even when you get past this high chlorine demand stage, you're gonna need to keep the cl between 5-10ppm all the time or you'll risk an algae bloom. So you're gonna need a kit that can test that high.

Run your pump 24/7 and backwash as needed.

By the way, don't use any dichlor shock or trichlor pucks. They are both stabilized and will cause your CYA to climb higher which is something you do not want.

Thanks!! You are right about the bleaching, my wife just called me from the pool place and we had a FC reading of 10.. hooray. I'm going to check out your link and grab that test kit this afternoon.

I don't remember what our CYA reading was when closing the pool and our pool has a vinyl liner. Any suggestions on how to improve the performance of our filter? I replaced the original filter two seasons ago with a brand new one. When should I change the sand? This will be the third season with the same sand.

Once I clear up our problem what do I need to do on a weekly basis to keep the water clear? Sorry for all of the questions this will be our first time using liquid chlorine and I just want to make sure that I'm doing it right.

While you are trying to clear the pool, test the water at least twice per day (early morning within 2 hours of sunrise and in the evening when the sun is off the pool) and each time, add enough chlorine to get it back up to around 20ppm. More often that twice per day is fine. There is no such thing as testing and dosing too much when you are trying to clear a pool. Run the pump 24/7 and backwash when you have a 5-10psi increase over the clean filter pressure. When you get to where you can go from sundown one evening to sunup the next morning without losing more than 1ppm of chlorine, then I'd run high cl levels one more day just for added insurance that everything is dead. Then, you can let the cl drift down and go to testing in the evenings only. With a CYA of 60, you'll need to keep the cl between 5-10ppm all the time. You'll test in the evening and add however much bleach you need to get back to around 10. If by the next evening, you have dropped lower than 5ppm, take it up to about 11 instead. You'll soon learn how your pool behaves. It may be with a CYA of 60 that you'll be able to add liquid chlorine every other day instead of every day.

You do NOT need to change the sand. I'm on my 11th season with my same sand; others may have had theirs for much longer. You also do NOT need to purchase any type of sand cleaner. It simply is not needed.

So, after this is all cleared up, the plan will be --- test chlorine every night, test pH at least a couple times per week. Test alk maybe once a month of so. If you start having pH swings, test alk more often. If you don't use any forms of stabilized chlorine -- and I wouldn't in your pool --- you probably don't need to test the CYA but maybe once more in another month or so. (Stabilized forms of chlorine are trichlor and dichlor. Don't use them.)

Hope this helps. Let us know if you have further questions. Buy the kit! You're gonna need it to be able to maintain this pool properly.

Thanks again for all of your help, you are a life saver!

You are most welcome. Come back if you need further help and also keep us posted how things are going! We'll be here!