Chlorine loss during day

[Ffejrengaw]

PH 7.6
CYA 40
FC (1hr after adding and before sunrise)5
CC 0
TA 80
24,000g pool

No matter what, 4 hours after sunrise FC is zero. Dump 1/2g of of liquid chlorine mid day 0FC by evening.

Converted from Baquacil this spring after letting the pool sit all winter (VT).

I’ve changed the sand
Pool is clear

I’m growing tired of dumping 1g of LC every night is this common? It’s rained 3 inches over the past month, I draw the water down before it rains, is CDX killing my stabilizer?

 

[Getitrite]

How are you testing?

 

[Ffejrengaw]

TF 100

 

[duraleigh]

In early Summer in Vermont, you should be losing about 2-3 ppm every 24 hours.

If you are losing more than that, I would suspect algae. Performing an OCLT would help define that.

 

[Bperry]

PH 7.6
CYA 40
FC (1hr after adding and before sunrise)5
CC 0
TA 80
24,000g pool

No matter what, 4 hours after sunrise FC is zero. Dump 1/2g of of liquid chlorine mid day 0FC by evening.

Converted from Baquacil this spring after letting the pool sit all winter (VT).

I’ve changed the sand
Pool is clear

I’m growing tired of dumping 1g of LC every night is this common? It’s rained 3 inches over the past month, I draw the water down before it rains, is CDX killing my stabilizer?

So you lose 5ppm 3-4 hours of daylight? That would be too much and indicative that the chlorine has been too low in the past. You should be maintaining the FC at 5-7ppm each day.

 

[Ffejrengaw]

How are you testing?

In early Summer in Vermont, you should be losing about 2-3 ppm every 24 hours.

If you are losing more than that, I would suspect algae. Performing an OCLT would help define that.

I’ve done that, it’s was 0 loss last week from 10pm to 4am, still went to 0FC by 10am.

 

[mknauss]

Welcome to the forum.
Can you provide a run down on how you converted from Baqua?
See Convert Your Baqua Pool to Chlorine

CDX complicates things. You might find it advisable to drain/replace a large amount of the pool water to remove it.

 

[koffey]

Ammonia?

 

[mknauss]

Ammonia?

No. Holds FC overnight.

 

[koffey]

Missed that, cheers!

 

[Ffejrengaw]

Welcome to the forum.
Can you provide a run down on how you converted from Baqua?
See Convert Your Baqua Pool to Chlorine

CDX complicates things. You might find it advisable to drain/replace a large amount of the pool water to remove it.

Pool was closed for in mid sept 22. Used Bacquacil +CDX for 10 plus years. Drained 20-25 inches at closing, did not add CDX or Bacquacil. Opened late may. Added LC to 15 for 2.5 weeks maybe 30-40 gallons of LC in the 12.5 to 10% range. Pool cleared , zero loss over night for three consecutive days. Still holds FC overnight but burns away during the day.

 

[mknauss]

Not an expert on CDX, but your symptoms imply it is still in the water.

Up to you, but a drain or exchange may solve the issue.

 

[Ffejrengaw]

Welcome to the forum.
Can you provide a run down on how you converted from Baqua?
See Convert Your Baqua Pool to Chlorine

CDX complicates things. You might find it advisable to drain/replace a large amount of the pool water to remove it.

Pool was closed for in mid sept 22. Used Bacquacil +CDX for 10 plus years. Drained 20-25 inches at closing, did not add CDX or Bacquacil. Opened late may. Added LC to 15 for 2.5 weeks maybe 30-40 gallons of LC in the 12.5 to 10% range. Pool cleared , zero loss over night for three consecutive days. Still holds FC overnight but burns away during the day.

 

[Ffejrengaw]

Should add I changed the sand in my filter after the first night of 0 ONCL.

 

[mknauss]

I am sure the Baqua goo was well gone so changing the sand then was fine. Just not sure about the CDX'

Lets ask @JoyfulNoise @Leebo for their take.

 

[Leebo]

When did you last test the CYA levels?

 

[Ffejrengaw]

When did you last test the CYA levels?

Yesterday, and about 4 days before that, and maybe 7 before that. It’s been 40 since I added chlorine stabilizer.

 

[Uckybay]

If you look back in this thread, you will see that I had the same issue. What it all boils down to is this explanation from JoyfulNoise:

The primary ingredient in CDX is an adjunct sanitizer that contains bromine. Your pool water is likely contaminated with a lot of spent bromide ion (Br-). When you add chlorine to the pool, the bromide gets oxidized to sanitizing bromine … great! … but unlike chlorine, bromine can not be stabilized by CYA against UV loss. So what you basically have is a pool with an unstabilized sanitizer in it. The UV light from the sun is essentially eating up all the sanitizer. You test kit is seeing the sanitizer (because both bromine and chlorine are detected by DPD), but the it’s half life from UV loss is about 40mins or so.

Sorry, but this is why Baquacil in general, and CDX in particular, is such a nightmare to deal with. Your only realistic option is to exchange drain the pool and get rid of as much of the contaminated water as possible. Either that, or your just going to have to ride it out with high chlorine consumption until you close the pool and you can drain it and refill it with winter precipitation.

I has been about 6 weeks since I fully converted from Baquacil to Chlorine, and just this past week I am finally able to keep chlorine in the pool during the day. I only had about 3 years worth of CDX in the pool...it sounds like you have probably accumulated a lot more over the course of 10 years.

I decided to only put chlorine in after dark since it was pointless during the day. It took a while for all of the Br- to be used and it's probably not the proper way to do it, but it worked for me.