Pool guy added too much shock and now FC is 40ppm

[SwimmingSparky]

Hi!

We have a new pool that is around 30,000 gallons. It was just filled in October and I’ve been letting the company that built it manage it thus far, thinking that was best as we were just starting out.

Today, the pool guy was here and noted the chlorine feeder for tabs was empty and chlorine level was zero. The water was clear and we do have an AOP system as well. He told me he was going to shock it, which seemed ok to do since they had let the chlorine feeder go empty.

In the afternoon that same day I noticed the water was clear but had a green tint. So I checked the log and saw that he added 6 pounds of “shock.” (I called later to see what this was and it was dichlor). I checked the chlorine level with the Taylor FAS-DPD kit and found it to be around 40ppm!

I’m concerned about damage to the equipment (gaskets, etc), plaster, natural stone on water feature, and the cover. Is there damage that could occur that wouldn’t be obvious until later on?

I called the company and they are coming out tomorrow. I asked if they would do a partial drain and refill, but he said they would probably use sodium thiosulfate… but it seems like it would take a lot to bring this level of FC down! I’ve read that this can be bad for surrounding grass… are there other issues with this?

Any advice would be greatly appreciated- thank you!

 

[mknauss]

Just let the FC go down naturally. I would not use any neutralizer. No big deal really. Your CYA is definitely high as 50% of the dichlor was CYA.

I would be more concerned with the pH. Be sure that is in the 7's.

 

[DrewLG]

I checked the log and saw that he added 6 pounds of “shock.” (I called later to see what this was and it was dichlor). I checked the chlorine level with the Taylor FAS-DPD kit and found it to be around 40ppm!

6 pounds of dichlor in your 30,000 gallon pool would raise FC by only 13ppm. Is it possible that you performed the FC test with a 25ml sample but counted each drop as 0.5ppm instead of 0.2ppm?

 

[SwimmingSparky]

6 pounds of dichlor in your 30,000 gallon pool would raise FC by only 13ppm. Is it possible that you performed the FC test with a 25ml sample but counted each drop as 0.5ppm instead of 0.2ppm?

Thanks for the reply. I used 10 mL of sample.

 

[SwimmingSparky]

Just let the FC go down naturally. I would not use any neutralizer. No big deal really. Your CYA is definitely high as 50% of the dichlor was CYA.

I would be more concerned with the pH. Be sure that is in the 7's.

Thanks for the reply. Glad to hear that maybe not as concerning as I thought! I checked the pH as well and it was around 7.6.

 

[Donldson]

I checked the pH as well and it was around 7.6.

the pH test is not accurate when FC is above 10 ppm.

If they said your FC was zero and added 6 pounds of dichlor, and now you're reading 40 ppm then you have a concerning problem. Either your FC was actually 27 and their testing is so bad it read zero, or they actually added 18 pounds of dichlor and lied to you. That is a pretty big red flag.

 

[SwimmingSparky]

the pH test is not accurate when FC is above 10 ppm.

If they said your FC was zero and added 6 pounds of dichlor, and now you're reading 40 ppm then you have a concerning problem. Either your FC was actually 27 and their testing is so bad it read zero, or they actually added 18 pounds of dichlor and lied to you. That is a pretty big red flag.

Thank you for your comment. How can the pH be checked in this situation then? The pH was 7.2 that morning and the only intervention was aeration by water feature for a few hours.

They did also add 4 tablets to the chlorine feeder in the same day and this was set to high, but I’m guessing that causes a very slow increase. I think it’s possible the chlorine wasn’t tested and assumed to be zero (and logged as zero) since the feeder had been empty. I also think it’s possible that they didn’t measure the dichlor but instead dumped in however much was left in their bucket and estimated 6 pounds.

But my main concern right now is if I’m going to have long term problems from this and what steps to take now.

Thanks!

 

[Donldson]

Any chance you can test your TA this morning?

 

[SwimmingSparky]

Any chance you can test your TA this morning?

I just checked and it’s 130

 

[Donldson]

Hmm. What are you using to test your pH?

 

[Bperry]

But my main concern right now is if I’m going to have long term problems from this and what steps to take now.

Only long term problem that’s obvious is the pool guys are going to goof up the testing and chemical additions each week. The solution seems obvious.

 

[SwimmingSparky]

Hmm. What are you using to test your pH?

I’m using the Taylor K-2006 kit

 

[Donldson]

I’m using the Taylor K-2006 kit

I think your FC might not be 40 ppm.

High FC causes phenol red pH tests to read high. However it is unlikely your pH is lower than 7.2 when you have a TA of 130 and a waterfall aerating the pool. Given that, I'd say the FC test might have been off.

 

[SwimmingSparky]

Only long term problem that’s obvious is the pool guys are going to goof up the testing and chemical additions each week. The solution seems obvious.

Ha ha! It sounds like the bottom line is that there shouldn’t be long term damage… that’s the main thing. Thanks!

 

[SwimmingSparky]

I think your FC might not be 40 ppm.

High FC causes phenol red pH tests to read high. However it is unlikely your pH is lower than 7.2 when you have a TA of 130 and a waterfall aerating the pool. Given that, I'd say the FC test might have been off.

That’s helpful info - thank you. The pH read I’m getting now is 7.6.

I’ll check the FC again today. Thanks again!

 

[Donldson]

It sounds like the bottom line is that there shouldn’t be long term damage… that’s the main thing.

Nobody said that.

You were told that the FC temporarily being at 40 when the CYA is well over 40 won't cause long term damage. This is accurate. The kind of poor water management that led to this situation, however, most certainly will.

 

[SwimmingSparky]

Nobody said that.

You were told that the FC temporarily being at 40 when the CYA is well over 40 won't cause long term damage. This is accurate. The kind of poor water management that led to this situation, however, most certainly

Nobody said that.

You were told that the FC temporarily being at 40 when the CYA is well over 40 won't cause long term damage. This is accurate. The kind of poor water management that led to this situation, however, most certainly will.

Understood, and I’m going to be more involved going forward. Thank you again - I really appreciate this forum!

 

[Bperry]

Understood, and I’m going to be more involved going forward. Thank you again - I really appreciate this forum!

If you want some extra advice, don’t let the pool service add anything at all or even testing the water. It’s ok to let them clean the skimmers and that kinda stuff if you trust them to do that and have lots of extra cash.

 

[SwimmingSparky]

If you want some extra advice, don’t let the pool service add anything at all or even testing the water. It’s ok to let them clean the skimmers and that kinda stuff if you trust them to do that and have lots of extra cash.

Yes, I’m working towards making sure I know how to do everything, so that I can take over and save some money. This forum is very helpful for learning the ropes!

Thanks all!

 

[TinFoilHat]

Get a TF100 or TFPro test kit, some liquid chlorine and take it over now. There's no need to use a pool service if you are home every day or every other day.