Newbie Chemistry questions

[UnderWaterVanya]

Last night's OCLT showed

10:30pm
FC 2.5ppm
CC 0.5ppm


7am
FC 1.5ppm
CC 0.5ppm

Water is clear.

I plan to start the shocking tomorrow when the kids go back to school. According to my reading, with a CYA of 80 (which I checked 2 days ago) I'll need to bring the FC up to 30ppm.

Overnight Chlorine Loss Test needs to meet the 3 criteria:

Lose 1ppm FC or Less
CC of 0.0 - 0.5ppm
Pool Water is Clear

While you seem to have passed, the OCLT is really intended to be done with higher FC levels so it's probably worthwhile to raise it up close to shock or up to shock and retest tonight.

 

[ladsjohn]

Maybe no reason to shock just yet.

1. Your pool water is sparkling
2. Your CC's are .5ppm or less
3. You can hold your FC overnight without losing more than 1ppm.

Sounds like you did all that...even though your FC is too low. I haven't read your entire thread but, at this point, I would pour in enough bleach to being FC up to around 6ppm and then turn up the SWG either through percentage or pump run time.

Thanks duraleigh,
The SWG runs at 100% for 8 hours a day. Perhaps the dog + kids are contributing to my low FC?

 

[duraleigh]

Perhaps the dog + kids are contributing to my low FC?

of course, anything that contributes organics into the pool. I would increase the run time up to 10 hours daily and see what happens.

Bring it to 6ppm FC with bleach first.

 

[Stuamurr]

Shocking would not do any harm, always good to give your pool a shock treatment on a regular basis as it reduces risk of micro organisms and other diseases which are undetectable to the majority sept in laboratory tests.

I would agree that shocking is not essential here but should be carried out on a fairly regular basis throughout the year, given that your chlorine levels were so low during the test last night and your CYA is high, the residual you do have in the pool will not work as efficiently as possible, so you should definately raise chlorine levels to 6-8ppm minimum (roughly)

Stuart

 

[jblizzle]

Shocking would not do any harm, always good to give your pool a shock treatment on a regular basis as it reduces risk of micro organisms and other diseases which are undetectable to the majority sept in laboratory tests.

I would agree that shocking is not essential here but should be carried out on a fairly regular basis throughout the year, given that your chlorine levels were so low during the test last night and your CYA is high, the residual you do have in the pool will not work as efficiently as possible, so you should definately raise chlorine levels to 6-8ppm minimum (roughly)

Stuart

I would disagree. There is no reason for periodic "shocking" if you have maintained adequate FC. However, bumping up the FC a few ppm before/after heavy use is always a good idea to ensure maintaining adequate FC.

I would agree, that if the FC has been allowed to drop too low on occasion, going through the shock process may be required and can be confirmed as necessary by performing the OCLT.

 

[duraleigh]

One of the things that makes BBB so attractive is that, through careful and accurate dosing and testing, you may not have to shock for an entire season.

I am pretty sure that periodic shocking got started as a "catch all" or "safety net" for people who didn't manage their pools carefully and it is an "easy" procedure for Pool Stores to teach.

Nevertheless, it is an added expense that can be very unnecessary if your pool water doesn't require it.