SLAM with no CYA....yes/no?

[EdKuhn]

So I know this guy who has a salt water pool and he's got a bad algae problem. The pool is heavy green with algae. He is low on salt but I told him to tackle the algae first with bleach and then worry about the SWCG. I'm initiating him into the TFP mindset and I hope he joins up. I brought my test kit over to his place and this is the result:

20,000 gal shotcrete pool with spa, Pentair IC-40 SWCG, and Pentair Easy Touch system, cartridge filter.

FC 0
TA 30
CH 175
CYA less than 20 (filled the tube basically)
Salt 1200

I forgot to run pH and CC. He has ordered his own TF-100 kit that will arrive in a day or two. Based on Pool Math it looks like 10ppm is the SLAM level with no CYA. I know his CH is low for a shotcrete pool, so is TA, but I figured he should jump on the algae first, after lowering pH to 7.2 or so if needed. There is a note about being careful with low CYA. Should we go ahead and SLAM away or get the CYA up a little?

Thanks!

 

[mknauss]

The water needs 30 ppm CYA in it or the chlorine burns off during the day prior to it killing the algae.
But, if it is a swamp, I would suggest doing this before adding any CYA:
raise your FC in the water using enough liquid chlorine to get to 10 ppm using PoolMath. Circulate the pool for 15 minutes. Test FC and CC. If FC at 5 or below, add LC to get to 10 using LC, circulate for 15 minutes, repeat until your FC is above 5 ppm after the 15 minute circulation.

 

[mknauss]

With a TA of 30, the pH is most likely quite low. I would suggest adding enough baking soda to get to a TA of 70. Then test pH after it is well circulated.

 

[EdKuhn]

With a TA of 30, the pH is most likely quite low. I would suggest adding enough baking soda to get to a TA of 70. Then test pH after it is well circulated.

Great, thanks very much. Hopefully there will be a new member joining soon!