Requesting Help with Improving Numbers

[NeilH]

Hello,

I would like to get some assistance in getting my pool chemistry up to snuff. I have a 35K gallon SWG plaster pool.

I went on vacation for two weeks and had the local pool store maintain the numbers. When we got back, I used the cheapo test strips and found that the FC wasn’t even registering. I brought the water to the store for testing. FC was 1.3, CYA was 17, and PH was 7.5. They said that other than the low CYA, everything looked great. They suggested that we increase the CYA but said nothing about raising the FC. Shouldn’t I be worried about the low FC? Based on their suggestions, I added 12lbs of conditioner on Sunday to bring up the CYA level.

In the meantime, I bought the TF-100 test kit so I could more closely control the numbers. I tested yesterday afternoon: FC was still very low, CYA was 45 and PH was 7.5. I’m also starting to see green algae growing in the pool. We had algae earlier in the year and back then, based on their suggestions, I shocked the pools with granules and added Biogaurd Banish. The algae went away for a month, but now it's back. Other than that, the water looks clear.

I would love some help on the best course to fix the problems. I'm a relatively new pool owner. If I throw a bunch of chemicals in the pool and screw it up worse, my wife will kill me. My guess is that I need to bring up the CYA to 70-80 and shock the pool to stop the algae. If this is case, can you do both at once or is there an order to follow? BTW, I plan on keeping the pool open for another 3-4 weeks.

Thanks!

Neil

 

[Butterfly]

Don't add any more CYA until you are completely done shocking. Higher CYA requires a higher FC shock level, ie more chlorine = more jug hauling and more $$. (It would have been less expensive to shock at a lower CYA level, esp with the huge pool size.)

We recommend bleach/liquid chlorine to shock the pool. Shock level for 45 CYA is 16 to 20 FC.
Follow the shock process in Pool School.

We'd also like to see a full set of test results from your kit

FC
CC
pH
TA
CYA
CH

 

[ping]

You have not had enough chlorine in the pool and that is why you have the algae. You will need to go through the shock process, pool-school/shocking_your_pool, until your pool passes the OCLT pool-school/overnight_fc_test, CC<.5, and the water is clear. Do not add any more CYA until you are finished with the shock process. By adding 12lbs of CYA you raised your CYA 40 points and you should now shock your pool using 60 for the CYA. It can take a week or so for the CYA to fully register in the test.

Please post all of the parameters:
FC
CC
pH
TA
CH
CYA

Using the FC/CYA chart in Pool School, pool-school/chlorine_cya_chart_shock, you need to keep FC at 24+.

Keeping your CYA in the 70-80 range is ideal for pools that use a SWG and keeping the FC at a minimum of 4 will keep your pool in great shape. Use the pool calculator, http://www.poolcalculator.com/, to calculate how much of each chemical you need to add to your pool.

 

[NeilH]

Thanks for the response. I am at work now but I will post the full test results later today.

How do I know the percentage of chlorine in liquid bleach? I used the pool calculator and I'm looking at almost thirteen hundred ounces of 5% bleach!

Am I correct in assuming that the FC level will eventually fall into the desired non-shock level? When do I starting bring the CYA level back up to the 70-80 range?

Since it takes a week for the CYA level to register, which number should I use as the basis for desired shock level?
Sunday morning it was 17 per the pool store test, conditioner was added Sunday night, last night it was 40 per my testing. If you're saying I raised it 40 points, should I use 57 as my CYA reading?

Thanks again. We bought our home a year ago. The prior owner told us that upkeep of the pool was easy. She never added chemicals to it. Just salt when the levels were low. I'm starting to think we're either doing something wrong or she was crazy.

 

[Butterfly]

Thanks for the response. I am at work now but I will post the full test results later today.

How do I know the percentage of chlorine in liquid bleach? I used the pool calculator and I'm looking at almost thirteen hundred ounces of 5% bleach!
The bottles have the % sodium hypochlorite shown as ingredients.

Am I correct in assuming that the FC level will eventually fall into the desired non-shock level?
Yes
When do I starting bring the CYA level back up to the 70-80 range?
After you are completely done shocking. See red lines in my sig.

Since it takes a week for the CYA level to register, which number should I use as the basis for desired shock level?
Sunday morning it was 17 per the pool store test, conditioner was added Sunday night, last night it was 40 per my testing. If you're saying I raised it 40 points, should I use 57 as my CYA reading?
Well, I suggest you go ahead and use 60ish for CYA and 24 shock level, as ping noted.

Thanks again. We bought our home a year ago. The prior owner told us that upkeep of the pool was easy. She never added chemicals to it. Just salt when the levels were low. I'm starting to think we're either doing something wrong or she was crazy.
The SWG system is one of the easiest, if not THE easiest systems; however, everything has to be balanced and stay that way to make your pool trouble free.
But, she could have been a little crazy if all she thought the pool needed was salt

 

[R.J.]

Don't forget to turn off your SWG while shocking. And get ready to add a lot of bleach; after the initial dose you need to keep adding enough to maintain shock level. Good thing you got the good test kit, too, you'll be doing a lot of testing. Good luck!