Should I Drain Pool Now or Wait for End of Summer?

[arizonasun]

Hi,

Thank you all for your help in advance. I am in Chandler, AZ and have been learning a lot about my pool thanks to this forum. I obtained the Taylor 2006 kit and performed a test today with the following numbers:

PH 7.4
FC 5.5
CC 0
TA 70
CYA <30 (I could still see the black dot even when filled all the way to the top)
CH 850-1000 (I couldn't get an exact read since the color is between purple and blue in this range)
Salt 4490

My questions:

1) Should I drain the pool now to lower CH? What risks do I run maintaining a pool with such high CH? Will this affect the life of the SWG? My salt level is also high which would be improved by a drain.
2) Pool stores are getting different numbers on the CYA. I have run the test three times now with consistent results (sub 30) with my home kit. Should I go ahead and add some conditioner? With a CYA of less than 30 shouldn't the FC drop very quickly during the day? How can I be sure that I need more in the water since this can't be reversed once adding?
3) I have had roughly 10 black algae spots pop up over the last few weeks while I was maintaining FC around 1.5-2. Given this history of black algae, what level should I keep the FC at now and into the future?
4) I am currently treating the black algae by brushing with a stainless steel brush and rubbing a trichlor puck on the algae spot. Should I continue with this and keep my FC at a certain level, or initiate a SLAM process and stop with the trichlor puck?

Thanks!
-Arizonasun

 

[bridgman]

Probably wouldn't hurt to do a CH test on your fill water. IIRC you're in an area where water from the tap has high CH already.

AFAIK you can run with fairly high CH but you need to manage pH and TA more carefully.

One trick for the CYA test is to pour the water/reagent mix back into the measuring bottle and then repeat the "pouring it in until the dot disappears" test as many times as you need to be sure. Make sure you shake & wait for 30 seconds or more to give the mixture a chance to cloud up.

Since you have an SWG the lower CYA level means it needs to work harder -- what settings and pump runtime are you using now ? Taking CYA up should mean you can lower SWG settings or pump runtime.

The recommended values in PoolSchool don't go down to CYA=30 for an SWG, but for manual chlorination the recommendation is to never go below 2 and target 4. With an SWG I believe you can go a bit lower but I would aim for somewhere between 2 and 3 to be safe.

http://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock

I'll pass on #4 and hope someone with more expertise than me sees it.