Brown Algae - SWG - Chemicals out of whack - Attack order?

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pointledge

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Aug 4, 2009
18
Chesapeake, VA
My first pool. Took a water sample to the local pool store and added stabilizer, salt, TA reducer following their directions. It's been 10 days and the pool has seen moderate use and the area has received almost daily rain storms. I've used some dry acid to bring the pH down (it keeps rising) and some chlorine tablets to help the SWG. The water is clear but brown algae has recently started showing up despite my brushing and efforts.

I know my chemicals are out of whack, I'm just unsure in what order to proceed to fix them (CYA first?).

I'm waiting delivery of my chemical testing kit so stuck with simple dip sticks right now. Currently these are the numbers I'm getting:

TH - 200
FC - 1
pH - 8
TA - 180
CYA - 50

The pool is 38,000 gallon, in ground, SWG (Chlormatic CM601), solar heated, with a DE filter.
I've backflushed the filter twice in the last week as the pressure rises (I assume the algae is clogging it) and am ready to pull it apart to clean as needed.

Please advise the order in which I should proceed. Thanks.
 
1) Adjust PH
2) Add LIQUID chlorine or bleach
3) continue monitoring you FC and PH and adjust as needed

read pool school a few times. All the answers you need are there. You are reaching the proper level of CYA for SWG, you don't want to go over or you will have to drain and refill to bring it down.

Once the pool is clear you can start working on bringing down your TA. Lower TA will help stabilize your PH rise, resulting lin ess addition of MA.

Also, read pool school. :-D
 
I agree, adjust the PH down to 7.2 ASAP

Shock the pool with bleach, and once you have an FAS-DPD test, perform an overnight FC loss test
(Instructions for shocking the pool and performing the overnight loss test are in pool school)

Also read Water Balance for SWGs. Your TA is a bit high and your CYA a bit low. Bringing these into range and maintaining proper FC levels (refer to the CYA chart) will prevent future algae issues.
 
Thanks. Been religiously reading this site and the school since I moved in two weeks ago. I suspect my SWG is on the fritz but will need my test kit to arrive to confirm.

I added muriatic acid to bring the pH down and added some bleach to start bringing the chlorine up. Didn't notice any new algae growth this morning. According to the pool calculator, I'm looking at ~14 gallons of bleach to bring my FC up from 1 to 24 to shock. Does this sound right? Is this still cheaper than buying shock chemicals from the pool store?
 
If your CYA is 50 your shock level is 20.

Bleach doesn't add any unwanted additives or have any unwanted side effects so yes, in the long run it is cheaper, especially if you can find a good price. Make sure you are calculating the correct jug size, most 6% bleach doesn't come in gallons.

96 oz jugs are $1.29 at Aldi
182 oz jugs are $2.54 at Wal-mart (store brand)

If you can find gallon size (128 oz) of 10-12.5% strength at pool stores for $2.50-3.50 each that is a good price and means less jugs to carry.
 
pointledge said:
According to the pool calculator, I'm looking at ~14 gallons of bleach to bring my FC up from 1 to 24 to shock. Does this sound right? Is this still cheaper than buying shock chemicals from the pool store?
Click to expand...

I have a sale notice from Leslies Pool that has Power powder Shock (cal hypo 68% I think) at $2.79 per lb, and it would take 14 lbs to do the same thing. So, yes, it is cheaper.

Plus that cal hypo would add 20 to your CH.
 
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