Speeding through bleach

[EddieO]

I am going through 2 gallons of bleach a day in my 21200 gallon AG pool. I had a little algae a couple of weeks ago. I shocked the pool and now my pool is crystal clear. However everyday, my FC reading is around 2 and I bring it up to 7.
All of my other readings are good, CYA is 40.
Is this normal?

Eddie

 

[Texas Splash]

Eddie, 2 gallons a day for your size pool is not normal. FC gets lost from two ways: the sun or algae/organics in the water. Your best option right now is to raise your FC to SLAM level or at least an FC of 10 and perform an OLCT. If you pass the OLCT, then you know it's the sun and perhaps CYA needs to be adjusted. Seeing however that you had algae recently and merely "shocked" the pool, it's very possible you never really completed or finished a true TFP SLAM.
- Do the OLCT first; if you fail, it's confirmed - SLAM. See the links in my signature for specific information to help you SLAM.

Let us know if you have any other questions. Good luck!

 

[jaduck]

If you are using 8 ppm/day I would consider that an elevated usage. Have you performed an Overnight Free Chlorine Loss Test (OCLT) and what type of test kit are you using?

 

[tim5055]

It sounds like you beat the algae back, but did not eradicate it. This is why we do not shock pools, but conduct a SLAM which is a process based on testing to prove that everything growing in the water is dead.

Time for a little Pool School and reading up on the SLAM.

 

[EddieO]

Slam is what I did. I said shock but it was a slam. I brought the FC reading to 24. However I didn't do the overnight test. I don't understand why the pool is so clear, algae is gone but it still needs so much bleach.
I think I slammed the pool about 8 says ago to be exact and there isn't any traces of the algae that was in the pool.

Eddie

 

[tim5055]

Slam is what I did. I said shock but it was a slam. I brought the FC reading to 24. However I didn't do the overnight test. I don't understand why the pool is so clear, algae is gone but it still needs so much bleach.
I think I slammed the pool about 8 says ago to be exact and there isn't any traces of the algae that was in the pool.

Eddie

The algae is not gone - just bringing the FC level to shock is not a SLAM. You must maintain FC at shock level until all 3 criteria are met

Clear water
Less than .5 CC
Pass OCLT

If you don't pass all three you run the risk of a low level algae colony staying in the pool. You may have clear water, you can't see the algae, but it's there. The chlorine is trying to get it, thus the high consumption level.

Re-read the SLAM directions and follow them to the end. It will eradicate the algae.

 

[EddieO]

Ahh I see. I'll slam it again. I have bags of shock in my garage. Can I use that or should I stick with bleach?

Eddie

 

[EddieO]

Never mind. I found my answer. Don't use Dichlor.

 

[jeffbrig]

That's not a hard and fast rule. With a CYA of 40, you could still use dichlor if you wanted to bring your CYA a little higher. I'm perfectly happy running mine around 50-55, since my pool gets a ton of strong sun exposure. It's just a question of how low or high you want to maintain your level.

 

[tim5055]

Never mind. I found my answer. Don't use Dichlor.

if you would update your profile with your location it would help us give more specific answers. If you were in Ft Lauderdale like Jeff, then higher CYA might not be the end of the world and you could use some dichlor, but if you are in Vermont I would say stick with 40.

I run 50 here in the center of SC.

 

[BobbyR]

Trust these guys when they say there's algae lurking in your pool. At 2 gallons a day with CYA at 40 there's no other explanation. You'll know when the last of the algae is eradicated because chlorine demand will suddenly just drop from one day to the next. My pool is a bit larger than yours and gets full sun for much of the day and I use less than half a gallon of 12% a day.

 

[440dodge440]

I looked at pool math and it says to go from FC=2 to FC=7, you need 157oz of 8.25% bleach. This is 1 gallons, 1 quart....Not trying to nit-pick, but saying you're adding just over one gallon/day may change people's answer. Or if you are adding 2 gallons per day, are you going to an FC=10?