Good job working blind, justFillitin -- I can't wait til you have the test kit
Re:water swapping...how you get your cya down (once you have the means to test it) is up to you....but study the cya:chlorine chart (link in my signature) so that you're very comfortable with the ratios if it will be a moving target for you during the slam.
Normally, having the cya where you want it to begin the slam makes a little more sense because to do a partial drain AFTER you've used all that chlorine and filter time to clear your water is kinda wasting the effort a bitA partial drain before just saves on bleach cost and filter time to get clear, so it expedites the process.
Its also a bit easier to slam with a lower and known/stable cya value...because to make the fastest process you are methodically testing and dosing in a way that never let's the slam value fall. A its cheaper to be dosing frequently to a lower slam level than a high one...as much as 30-50% cheaper
So whether you actively drain now, or use vacuuming to waste incrementally over days, the single most important part for speedy recovery is actually maintaining the shock/slam value to cya ratio, which is why the test kit was so critical to the process.
Eg if your cya:FC slam level was 24, for example, and you add to 24 at 8 a.m., then don't check for 2 hours, you will have spent the majority of those 2 hours between tests at less than your slam value, which gives the algae a chance to outpace you and drags out the process.
If instead you dosed a bit above that to account for the drop, you will spend more time in the effective range. (In my case, my cya was low, so if I was aiming for say 12, I'd dose to 16 initially and then see if that "lasted" til the next dose in 2 hrs...) You just don't want to overdo the overdosing because you don't want to bleach the liner or waste bleach.
So, "maintaining" is the critical part, whatever your cya:FC ratio at shock/slam level.
Slamming during the work week is a bit tougher in that you might only be able to check in a.m. and after work. If you are able, it will help if you plan to come home at lunch.
In your case, it sounds like you've already broken its back somewhat and you may find your chlorine holding decently.
Keep us posted and cheers to imminent clearing!
I looked at the chart you mentioned in your sig. I understand the relationship, and appreciate the tips. I think after the vac and brushing tonight, CYA should be close to nominal. I will confirm this when I get the kit TOMORROW!!!

