Preparing to SLAM my green pool

[mbaskerv]

I opened my pool for the first time after two full seasons covered, and as you may imagine it's a green mess. I've taken some time to read through Pool School, got my TF-100 Test Kit and ran some numbers through Pool Math, as I am ready to SLAM the pool, but wanted to get some input from the experts here at TFP before I get started.
Current numbers (20,000 gallon vinyl lined pool, 48 sq ft DE filter):

CYA < 20 ppm ... FC = 0 ... pH = 6.8 ... TA = 90 ppm ... CH = 200 ppm

For a SLAM, I think I need to get the FC up to 12 (shock level) - so my targets will be as follows:

CYA ~ 35 ppm ... FC = 12 ... pH = 7.5 ... TA ~ 100 ppm ... CH = 200 ppm (I think my Calcium hardness is within range?)

PoolMath returns the following:

2 gallons 1.5 qts 10% chlorine to achieve shock level of FC ... 6 lbs. 11 oz. washing soda to raise pH ... 2 lbs. 15 oz. baking soda* to raise TA ... 2 lbs. 8 oz. stabilizer to raise CYA
* since the baking soda will also raise the pH, should I compensate by adjusting the amount of washing soda, or vice-versa?

My understanding is that I need to get the pH and TA to the target numbers before I start dumping in the chlorine (I'll be using 10% liquid chlorine from WalMart). Is there a sequence I should follow, or should I add the recommended amounts all at once?
I'm also concerned that I will need (very) frequent back washing since there is a lot of algae - I've tried to get as much crud off the bottom as I can, but since I can't see the bottom I can't be sure that I got it all. I was running the filter in "recirculate" before I got the test kit, as I found the filter was clogging within minutes with all the algae and no chlorine. I think the "formula" for back washing is to add 75% of DE capacity for each "cycle" (three pounds in my case) - this could get pricey - At this rate I'm concerned that I will have to be prepared to backwash every 15 minutes??? I should probably pick up a new box of DE.

I have found this site an invaluable resource and look forward to getting in the pool for the first time in two years! Thanks in advance...

 

[woodyp]

Fix the ph--ignore the TA--and SLAM on!

 

[Richard320]

Frankly, if the pool is green, you'll be replacing so much water from backwashing that I think it's a waste of time to try balancing everything to perfection. The algae is growing as I type.

Measure out enough CYA to get to 30ish and hang it and then immediately start with the bleach. All the brushing and vacuuming and 24/7 filtering will drive the pH up. Not to mention all the water replacement.

Rebalancing after the algae is gone can be done in a matter of an hour. Kill the algae.

 

[mbaskerv]

So for now I should focus on adding washing soda (raise Ph) and stabilizer to get the CYA to ~ 30 -35 ppm, and then hit it with the chlorine, brush, vacuum, backwash and repeat?

- - - Updated - - -

I understand the need to run the filter 24/7, but if the pressure rises so rapidly, I'm hesitant to let it run unattended - should I switch to recirculate when the pool is unattended?

 

[Richard320]

So for now I should focus on adding washing soda (raise Ph) and stabilizer to get the CYA to ~ 30 -35 ppm, and then hit it with the chlorine, brush, vacuum, backwash and repeat?

- - - Updated - - -

I understand the need to run the filter 24/7, but if the pressure rises so rapidly, I'm hesitant to let it run unattended - should I switch to recirculate when the pool is unattended?

Probably a good idea.

 

[mbaskerv]

Thanks - I'll get my supplies and plan to hit it over the weekend!

 

[Richard320]

Thanks - I'll get my supplies and plan to hit it over the weekend!

Why wait? You can find bleach all over the place. Hit it once when you get home, again at bedtime. and once more before you leave for work and 80% of the algae will be dead already. There will be no FC loss to sunlight overnight, so you could get a really good kill on it. Over the weekend you can deal with the vacuuming and backwashing.

 

[mbaskerv]

Thanks Richard. I'll let you know how things work out.