I can't seem to keep a FC level above 1.0.

FC-1.0
CC-0
PH-7.6
Alk-90
CYA-50
Temperatures have been 95-100 degrees-don't know if that matters.

We had a problem when we opened and used bleach until we got it corrected.

Everything's been fine since then up until the last week. I had been adding 10 - 15 ozs. cal-hypo every other day depending on reading. For the last 5 days, I can't get a FC reading higher than 1.0. I even tested one time 4 hours after my husband added 16 ozs. I still only got a reading of 1.0 FC.

I'm using a Taylor K2006C test kit. I ordered and received new reagents the beginning of June. I test and add chemicals at night.

I'm a bit perplexed. Does this sound normal?

I forgot to add:

18 x 33 ft. above ground pool -13,700 gallons.

No, it does not. But, the fact that your chlorine has dipped so low may be causing a chlorine demand if you have an impending algae bloom.

On the other hand, could it be testing error?

Watch these testing demos to verify that you are doing it correctly.
http://pool9.net/K2006-vid/

If you are certain that you are, then I would advise going ahead and shocking the pool. Add 3 of the 121-oz jugs of generic 8.25% bleach. An hour or two later, test again and make note of the FC and CC readings. Then, in the morning within an hour of sunrise, test FC and CC again. Post your evening and morning readings for us to see.

I didn't arrive home to read your post and test until 11:00 pm last night. My husband cannot test. He's color blind and cannot tell when it turns clear. He added 12 ozs. cal-hypo after I left for work yesterday morning at 5:15 am. I tested at 11:00 pm.
fc 0.5
cc 0
ph between 7.6 and 7.8
alk 90
cya 50

We didn't have any bleach or any stores open at that time of the night so my husband went first thing this morning to buy the bleach. He put the 3 gallons in around 6:00 am. However it could not be tested until I arrived home at 6:00 pm.

fc 9.0
cc 0
ph 7.8
alk 90
I assume the cya is still the same.

Why would it hold the fc reading with bleach but not with cal-hypo? I would say I might have gotten a bad or old batch of cal-hypo but I've been using this 25 lb bucket of cal-hypo since 6/7/1 and did not have a problem holding a chlorine level until now. We started out with dichlor because I couldn't find any cal-hypo, but it was raising my cya too much.

ph 7.6-7.8 actually still between these 2 colors
alk 90

Should I lower the ph by adding ph down, then add about 72 ozs. 8.25% bleach? or just add bleach or cal-hypo to see if it holds a fc level with that this time?

Your pH is fine. Don't worry about it.

Like I told you before, I think you are on the verge of an algae bloom and that is why you can't hold a chlorine reading. You are letting your chlorine levels drop too low. With a CYA of 50ppm, your chlorine needs to stay between 3-6 all the time. Dip below that and algae will start. Did you ever shock your pool as I suggested above? If not, you need to or you will never get past this and at some point, the pool will probably turn green. Your shock level will be 15ppm. http://pool9.net/cl-cya/

In your pool, each quart (32 oz) of 8.25% bleach will add about 1.5ppm of chlorine. Each of the 121-oz jugs will add about 5.7ppm. Test your pool and add enough bleach to take your chlorine up to about 15. You need to continue to add enough bleach to stay at shock level until three things occur:
1) You can go from sundown one evening to within an hour or sunrise the next day without losing more than 1ppm of FC overnight.
2) You have no greater than 0.5ppm of CC
3) Your pool is clear.

Yes, we shocked it. We added 3 gallons of 8.25% bleach at 6 am the morning (7/16) after I read your post. That evening the readings were
fc 9.0
cc 0
ph 7.8
alk 90

Tonight (7/17) readings were

fc 4.5
cc 0
ph 7.6-7.8
alk. 90

We have been keeping it between 5-7ppm until the last week when I started having this problem.


I'm sorry, I didn't realize I need to keep it at shock level so I didn't add more bleach since it was still at 9fc with no cc last night. I tested tonight

Ok. Test it this evening and go ahead and add enough bleach to get back up to shock level. Until you can hold a chlorine reading overnight without losing more than 1ppm of FC, continue to shock the pool daily. Once you pass the overnight test, we typically suggest keeping the chlorine high for one additional day for added insurance and then you can let your chlorine drift down. (By the way, it is best to shock the pool in the evening. Then, an hour or two later, test your chlorine so you'll have a reading to compare to the next morning.)

Keep us posted how things are going.

(No need to test alk every day unless your pH starts bouncing around. As long as pH is stable, testing alk once every week or two is fine.)

Thanks!

Once again, you guys are the best! I wish I had found you guys when we first bought our pool in '93. We wouldn't have gone with Baquacil and had that nightmare of an experience. You guys got us through the conversion and it's been great since. ..well a few hiccups but y'all always help me through it.

Thanks for the tips. I usually shock/add all chemicals at night but ran out of bleach and had to wait for store to open to buy more this time. I didn't know I don't have to test alkalinity every time. I've been testing ph and alkalinity every time, but not CYA.

I just tested.

fc 7.0
cc 0

I'm taking it back to shock level and will test again in 2 hours as suggested, then first thing in the morning.

Thanks!