Testing FC No pink BUT….

[Surplum]

I installed a new pool last week. For kicks I did the Taylor DPD test before adding any sanitizer, and it stayed clear.
Added a gallon of 10% chlorine day before yesterday and tested 24hrs later with dpd, didnt turn pink, even after 15 scoops.
My question is, I left a 2nd test sample of the 10% LC only-treated water in the tube sit out for about 24 hours. It had maybe 5 scoops of dpd powder. Was clear yesterday. But this morning, it’s pink. What happened there?

 

[woodyp]

Out of the sun maybe. What is your CYA level?

 

[Sunnydaze]

I installed a new pool last week. For kicks I did the Taylor DPD test before adding any sanitizer, and it stayed clear.
Added a gallon of 10% chlorine day before yesterday and tested 24hrs later with dpd, didnt turn pink, even after 15 scoops.
My question is, I left a 2nd test sample of the 10% LC only-treated water in the tube sit out for about 24 hours. It had maybe 5 scoops of dpd powder. Was clear yesterday. But this morning, it’s pink. What happened there?

The test is invalid after sitting for a period of time. You had/have zero chlorine and used a bunch of powder to determine that. If it doesn't turn pink after one scoop (assuming you're using 10ml, 2 scoops for 25ml) then you have no chlorine.

What's your cya level? Is the water clear? 1 gallon should have increased your FC by 12ppm. If it was all gone in 24 hours, you either have no cya and/or something consuming your chlorine. Or the chlorine was degraded and didn't actually add any FC to the pool.

 

[Mdragger88]

Your dpd powder could also be bad - is it discolored (very dark) or extremely clumpy? I would add more liquid chlorine then test after 30 minutes & see where that gets u.
Also you could test your tap water to confirm your powder is good - mine always has some fc.

 

[Surplum]

The test is invalid after sitting for a period of time. You had/have zero chlorine and used a bunch of powder to determine that. If it doesn't turn pink after one scoop (assuming you're using 10ml, 2 scoops for 25ml) then you have no chlorine.

What's your cya level? Is the water clear? 1 gallon should have increased your FC by 12ppm. If it was all gone in 24 hours, you either have no cya and/or something consuming your chlorine. Or the chlorine was degraded and didn't actually add any FC to the pool.

No CYA at that time and it was raining ALL day, ive since added dichlor. I suspect it was a bad batch of liquid chlorine. Dont know enought about dpd to know why it would pinken after 24 hrs. Despite my 20 year old chemistry degree.

 

[Pv2]

it will turn pink after a much shorter time than 24 hours especially with 15 scoops (???!!! why would you do that?), and it will turn BACK to pink if you let it sit after you get your reading when it clears from the drops as well.

you may have lost your chlorine in 24 hours - that depends on volume of water and what else is in it (such as no CYA, algae, dirt, etc)

 

[Surplum]

I was curious . The instructions do say to add until it turns pink.
Another question? Would you add stabilizer to a new pool or just let the trichlor pucks add it up until it’s at a normal level? Im at about 15 now (guestimating bc the taylor test doesnt go that low?)
I plan to switch to bleach after im out of pucks.

 

[Surplum]

Your dpd powder could also be bad - is it discolored (very dark) or extremely clumpy? I would add more liquid chlorine then test after 30 minutes & see where that gets u.
Also you could test your tap water to confirm your powder is good - mine always has some fc.

It was slightly clumpy. Tested it 18hrs after the dichlor and got 8.6. Think the liquid chlorine was bad.

 

[Pv2]

I was curious . The instructions do say to add until it turns pink.
Another question? Would you add stabilizer to a new pool or just let the trichlor pucks add it up until it’s at a normal level? Im at about 15 now (guestimating bc the taylor test doesnt go that low?)
I plan to switch to bleach after im out of pucks.

personally, I would save the pucks for vacation or travel time and get cya and chlorine up where it needs to be unless there is a shortage for some reason (another reason to hang on to the pucks - future shortages)

pool math can help you figure out where you are but testing is best (even though that test is the most subjective) plug in for "effects of adding"

 

[Surplum]

personally, I would save the pucks for vacation or travel time and get cya and chlorine up where it needs to be unless there is a shortage for some reason (another reason to hang on to the pucks - future shortages)

pool math can help you figure out where you are but testing is best (even though that test is the most subjective) plug in for "effects of adding"

Excellent point. Thanks!