Hopefully...minor clarity issue

[buki5]

Perfect. Thanks. I've referred to the Best guess table a number of times. So, I think I can do that. And yes will likely drain sooner rather than later....then I get to start the chemistry all over again.

[Watermom]

then I get to start the chemistry all over again.

We'll be in your back pocket helping then, too! Have fun swimming this weekend!

[chem geek]

Losing more than 50% of the FC in a day with a very high CYA level means you've got more than just loss from sunlight. You could check the overnight chlorine loss, but I suspect you've got nascent algae growth even if it isn't visible -- again, if the CYA reading is truly as high as reported.

Usually even in very hot sunny weather the chlorine loss will be around 15% in a day when the CYA is 100 ppm or so. At 60-80 ppm it may be around 20-25% FC drop while at 40-50 ppm it may be up to 50% and at 20-30 ppm it could be up to 60%. Higher CYA levels have lower chlorine loss rates even when proportionately keeping the FC higher. It may have to do with some direct CYA shielding effect protecting lower depths from sunlight.

[buki5]

Thanks again all.

I've been testing CL levels at least 2 times a day to understand what is happening. The run down of the last 20 hours or so is this. Weather is Sunny and warm.

Last night added the extra bleach suggested by Watermom. I was at 11.05 plus another bottle which should have taken me to around 14.5. Checked this morning before work (left pool open overnight) and measured around 14. Covered the pool for the day, came home and measured again (about 11 hours) and got a 12.5. Kids swam, dog swam, I swam (2.5 hours passed, I checked CL again and measured 8.5. Added 2.84 gal 6% and leaving open overnight. Will measure before I go to bed later and expect a 14.5 to 15 reading. Will check again in the morning. My money says it will be in range of 13 to 13.5 then when I get home am expecting around 11.

Will keep you posted.

[Watermom]

Sounds like you are getting control of this pool! I still think, if it were me, that I would do a partial drain and refill, but glad you are getting to swim some. After all, that is what having a pool is all about! Have a great weekend!

[buki5]

Couple more things...
Do I understand correctly that the belief of the BBB method is that you only need to shock if you are having or starting an algae or known pathogen problem? I'm referring to the PS statement of shocking weekly?

Also, RE: CYA testing I've tested using the add 7oz water then add 7oz regent shake like hell then drop until you can't see the black dot enough to go through a little over 2 bottles (.75oz) of regent. Every single time I don't get half way to the 100 mark before I can't see the dot. basically the fluid drops out almost white. The first couple of times I thought for sure I was doing something wrong but in reading I haven't seen anything to have me do any different and my tests have been consistent.

For background this is a pool with a power cover and the Pentair 300 3" tab chlorinator adn when I moved in the valve on the Pentair was set at the max setting. I wouldn't be surprised if the majority of the water is years old and the prior owners were struggling to keep the water clear. Based on what I'm seeing on here Regarding the tabs I'm not real surprised...now. (although I was the first few times).

Brian

[aylad]

As far as shocking goes, there is no need to shock weekly just on principle--you need to shock the water if 1) it's cloudy, 2) you have a CC of more than 0.5, or 3)you start seeing indications of impending algae bloom. There are some people who never shock the pools except when getting ready for closing--and then there are those who shock more frequently "just because".

It doesn't surprise me that your CYA is that high, if tabs are all the previous owners used with this pool. It doesn't matter that the water is "old", but lowering that CYA will definitely make the pool easier to manage! Can you imagine what nightmares the previous owners had trying to get/keep it clear?

Janet

[buki5]

Two consecutive posts. While I'm at it...RE: CYA.

Looks like if I want to raise my CYA level 5 ppm. It will take about 1 lb disolved in the pool.

18x36 9' deep end 3.5 ish shallow end rectangle.

When I did my CYA test it was full a little past the 30 marker and I think I could faintly see the dot at the bottom.

Everyone concur with adding the 1 lb of CYA. I'm skitish since I was way off the charts all of last year.

[Watermom]

In an 18K pool, each pound of CYA should increase the reading by about 7ppm. I think you can add 1 to 1-1/2 lbs to start with. Wait a week to make sure it is dissolved and then retest and then you can decide if you need to add more.

Regarding your alk, you can add some baking soda to bump it up some. Add a couple of lbs. at a time. Gradually increase your alk to somewhere between 80-110 or so.

[madwil]

I can understand your concerns on CYA, but anywhere in the 30-50 range should be much more manageable...
You can add the CYA in stages, add half, retest next week, then add the other half if still needed!
the alk boost will help over time, just don't overdo it...