Bucket Test

[kaptn]

Can you please explain what the Bucket Test is supposed to do.

2 gallons of pool water and add 1 teaspoon of 6% liquid chlorine equals 10ppm of FC. How do you find out what your chlorine demand is? do you keep adding teaspoons until you get a certain reading of FC?
Also do you test over certain intervals of time?

an example would be helpfull..

thanks

[chem geek]

It's 1/4 teaspoon of 6% bleach in 2 gallons that is 10 ppm FC -- not 1 teaspoon. 1 teaspoon would be 40 ppm FC.

1) Take a clean bucket and fill it with 2 gallons of pool water and take the bucket to a shady area or inside so that it is not exposed to sunlight.
2) Add 1/4 teaspoon of 6% bleach to the 2 gallons of pool water in the bucket and mix/stir briefly.
3) Wait 10 minutes and then measure the Free Chlorine (FC) level of the water in the bucket.
4) If the FC level is not near 10 ppm -- say it's below 5 ppm or even zero -- then repeat with step 2 above.
5) If the FC level is near 10 ppm (or higher), then wait one hour and retest; if the FC has dropped well below 10 ppm, repeat with step 2 above; otherwise stop this procedure and note how many 1/4 teaspoons you've added cumulatively NOT counting the last one. Multiply this number by 10 and this gives you the cumulative amount of FC needed to clear the pool such that the FC will hold. You can use The Pool Calculator to calculate dosages for the pool.

Note that to accurately test the FC level you should have a FAS-DPD kit such as found in the Taylor K-2006 or TF-100 you should have anyway. A DPD chlorine test (intensity of pink/red) may bleach out; an OTO chlorine test (intensity of yellow) won't bleach out, but won't give you an easily determined FC reading and actually measures Total Chlorine (TC) instead.

[kaptn]

thanks chem,

makes a lot more since. Do you keep doing step 2 until you get a reading of FC at 10ppm? Or do you just stop it at 30? and it only has to hold for one hour?

[chem geek]

It is best to do step 2 and then wait at least a short while before measuring the FC. However, if you mixed and measured right away and measured low FC, then you could add more chlorine. I only put in the waiting for 10 minutes to give reasonable reaction time, but you can shorten that if you wanted to. The point is to keep adding chlorine as long as it is getting consumed and then when it slows down you wait longer to give it more reaction time. When it starts to hold even over an hour, then the amount you added before that point is your estimate. Though you might need even more chlorine in your pool -- that will at least get you a decent estimate of the amount that will be fairly rapidly consumed.

[kaptn]

Well I gave this a try yesterday.

2 gallons of water and 1/4 teaspoon of 6% bleach. waited about 10 minutes and my readings were

FC 8.5
CC 1.0

1 hour later

FC 7.0
CC 0.5

I added another 1/4 teaspoon of bleach and waited another 10 minutes

FC 11.5
CC 0.5

2 hour later ( I wanted to see if there was a drastic movement)

FC 11.0
CC 0.5

I let this sit for about 7 hours overnight and tested in the morning....pretty much the same result

FC 11.0
CC 0.5

So does this basically mean that I need to keep a shock level of about 20?

[chem geek]

The bucket test doesn't tell you the shock level, but rather gives an estimate of the total amount of chlorine it will take before it starts to hold in your pool. It looks like the chlorine demand might be around 9 ppm FC which isn't too bad. So you could just raise the FC to the shock level which is an FC that is 40% of your CYA level and keep it there until your overnight FC drop is <= 1 ppm. Or if you prefer, you can just keep an elevated FC level, say at 15-20% of your CYA level, and eventually you'll get rid of the extra chlorine demand over time though it will take a bit longer.

[kaptn]

I put in 3 gallons of bleach in last night so I will check to see if I have any free chlorine tonight.

[kaptn]

well I checked my FC Chlorine this morning....did a simple test and it showed color around 2.5. Normally I would get like nothing. So even though it has come down it read some free chlorine.
Lets see if a gallon of bleach will raise my 18K pool FC 3.4 then about 8 galloons will shock it to about 27.2 Free Chlorine.

[kaptn]

got home Thursday evening and No Free Chlorine reading

So sum this thing up so far.

Free Chlorine Reading:

Tuesday evening 11ppm
Wednesday Morning 10.5ppm
Thursday morning 2-3ppm
Thursday early evening 0ppm
Thursday Late evening vacuumed up the little algae and all the daddy long legs that met thier pool destiny.
I shocked it with 8 gallons of bleach after vacuuming and got a 26ppm reading
Friday Morning 21.5ppm (added another gallon of bleach to bring it back up to about 25 range).

Pool looks beautiful and clean but I want to kill off this algae thats using all my FC all the time. Being that it went from 26 to 21.5 overnight is it safe to say that something is still using up my FC. How much FC do you lose from sunlight? I thought a higher CYA keeps it from burning out as quickly from sunlight?

Will check full stats after work Friday evening

[chem geek]

Being that it went from 26 to 21.5 overnight is it safe to say that something is still using up my FC. How much FC do you lose from sunlight? I thought a higher CYA keeps it from burning out as quickly from sunlight?

Will check full stats after work Friday evening

Yes, you've still got organics in the pool you are oxidizing -- probably dead algae at this point. You know you are done when the overnight FC drop is <= 1 ppm. As far as how much is low in sunlight, that depends on the CYA level but roughly speaking you lose around 15% of the FC when the CYA is 100 ppm, 20% when the CYA is 80 ppm, 40% when the CYA is 50 ppm, 60% when the CYA is 30 ppm though this very much depends on how much sun is on the pool for how long.

You really need to keep the FC up at shock level and not let it drop -- you'll just go backwards if algae are able to grow again which they may do if the FC gets much below around 4 ppm (assuming 70 ppm CYA).

Are you using a Taylor K-2006 or TF-100 test kit?

[kaptn]

I have a taylor 2005 and bought a DPD 0870 and 0871 regeants. I already had a 50ml tube from an existing kit so I can measure the 10ml for the testing.

[chem geek]

OK that's great.