Trying to Balance my water

[saccrestorations]

My pool is about 4 years old. I have only tested for PH and Chlorine using the OTO type test. I have always had a hard time keeping PH where it should be.

My pool is about 25k gallons and has a SWCG. I got a better test kit and my current numbers are as follows:

FC 1
TC 5
CC 4
PH 7.2
TA 140
CH 340
CYA 50

My PH is low because I am working on bringing the TA down. I have brought it down to 7.0 and am now using aeration to bring the PH back up.

My biggest concern is the FC. It was at 0 with the TC at .5. I ran my pool over night with the SWG at 95% and the FC came up to .5 with the TC at 1. At noon today I added 2 quarts of Chlorine and then checked my numbers at 5:00pm. As you can see above my FC is still only 1 but the TC came up to 5. That means my CC is around 4.

So I think this means I need to shock the pool. I read the “how to shock” topic but still have a few questions.

I think I need to bring the FC up to 24. The pool calculator says to add 5 gallons of Chlorine. Is that all there is to it? My test kit only goes up to 5ppm so I won’t be able to tell if I made it to 24. Also, how long after I shock will it be before the pool is safe to swim in again?

Any advice on how to proceed would be greatly appreciated.

Thanks, Scott

 

[polyvue]

I think I need to bring the FC up to 24. The pool calculator says to add 5 gallons of Chlorine. Is that all there is to it? My test kit only goes up to 5ppm so I won’t be able to tell if I made it to 24. Also, how long after I shock will it be before the pool is safe to swim in again?

According to Chlorine/CYA Chart by Chemgeek the suggested shock level for pool water with a CYA level of 50 is... 19.8 ppm. The Pool Calculator, if I've entered your numbers correctly, suggests a shock level of 16ppm.

At any rate, be sure about the strength of the bleach. Fresh Chlorox delivers about 6%, if its fresh; you'll need more than 7 gallons to initiate shocking. Most common liquid chlorine, available in pool and discount stores, is Sodium Hypchlorite 10% - about 5 gallons of this product is right to elevate FC to shock level. If you're using stronger pool supply chlorine (12.5%) you'll need less. No-name brand grocery store bleach that has sat on the shelf for months will provide less than 3%, so you'd need 15 gallons of that! Be sure you enter the appropriate bleach percentage in the calculator before deciding what amount to add.

On the positive side, shocking should be a bit easier with the pH as low as it is. Strongly recommend that you beg, borrow or steal a FAS-DPD chlorine test (from a local pool supply store, perhaps?) so you can measure FC more accurately and prepare diluted sample to ascertain the high amount of chlorine that will result from shocking. I think my kit will test up to 25ppm. Finally, I wouldn't think of letting my guests into the pool until the chlorine is less than 10 ppm and have a personal rule that no one swims until I find that the Combined Chlorine (CC) is unmeasurable -- for me, that means < 0.2 ppm.

Other more knowledgable folks on this forum will add or subtract from this advice.

Shocking:
1. Measure the FC level
2. Add enough chlorine to bring FC up to shock level
3. Repeat steps 1 and 2 as frequently as practical, as often as once per hour, and not less than twice a day, until:
a. CC is 0.5 or lower;
b. An overnight FC loss test shows a loss of 1.0 ppm or less;
c. And, if you don't have a FAS-DPD test kit, the water is clear.
Source: Shock Your Pool

 

[waste]

Scott, welcome to TFP!!

Polyvue has given you VERY good advice

You really want to invest in a better test kit, either the Taylor 2006 (Leslies sells the same kit, rebranded) or the TF- 100 (linked in my sig). When dealing with a huge cc level, like you have, or an algae issue the FAS/DPD test is the BEST way to go! - You'll save money and be able to be sure that the problem is properly addressed

 

[PaulR]

Hear hear to what the others have said.

I think in general you're best off if you think of the SWG as a way to maintain an FC level, or at best make small adjustments (on the order of 1-2ppm). If you're bringing FC up from zero, or trying to shock, you should use a chemical source, the exact one depending on what else you might try to do simultaneously. (Bleach/liquid CL if your other numbers are okay; dichlor if you want to raise CYA; cal-hypo if you want to raise CH.)
--paulr