TF-100 DPD chlorine -must be doing it wrong

[darthv]

Hello all,

I have a 30k plaster pool with visible algae on the walls. I drained half and refilled so I could get cya down. Prior to refilling I poured in 3 gallons of chlorine for SLAM

Got the TF-100 and tested. Showing ph 7.5. Simple chlorine test 5. Cya 40.

When I do dpd chlorine test got to 40 drops and the solution turned white but never “clear” so I stopped.

Now 24 hours later I tried again and solution turns from pink to white cloudy after 2 drops but never cleared after 20 drops

so I tried diluting my pool water by half thinking the chlorine level is just too highand tried again. Well after adding the dpd powder the solution is light pink but already looks clear so after two drops now it’s essentially clear white.

what could I be doing wrong? Seems like I’ll run through the whole kit without getting a true dpd chlorine reading

thanks

 

[mknauss]

Pool School - FAS-DPD Chlorine Test

Be sure to use 10 ml of water, then each drop equates to 0.5 ppm FC

The solution goes from pink to clear/white. It is not clear. So once the pink is gone, you have your result.

The test you describe above, "solution turns from pink to white cloudy after 2 drops" equates to a FC of 1 if using the 10 ml sample, or 0.4 if using the 25 ml sample.

Take care.

 

[darthv]

I honestly never realized how much chlorine is required for shock. I had to put in 8 gallons of 6% bleach to get to shock level of 16 and 12 hours later the tested FC level was at 7.5, so in goes another 4 gallons

A SLAM might cost hundreds if this persists.

QUESTION:
1. Also, if you maintain SHOCK level, do you have to really scrub or will the algae on floor and walls die off on its own at shock levels and get vacuumed up. I ask as some parts of the pool are not accessible with the brush (brush too short)?
2. is it necessary to waste ingredients on testing combined chloramines other than to see that it is positive? Do we make adjustments based on the amount of CC. I ask because there is a lot of CC left in my pool after all this.

Thanks

 

[Bama Rambler]

1. Scrubbing the pool during SLAM is fairly important because algae can possibly build up a biofilm that will protect the lower layers against the chlorine.

2. Not really. The only time it's necessary to test CC is during the OCLT. That's one of the criteria for passing the OCLT so that's really the only time you must perform that test.

 

[mknauss]

I would also look for a different bleach. Walmart Great Value is 8.25% and typically very fresh.

Do not use Clorox 'Cloromax' -- it has polymers in it that are not good for your pool water.

Take care.

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Could you add a signature? See Pool School - Getting Started

Also - how are you testing? Be sure to follow the [FC/CYA][/FC/CYA] and SLAM Process.