Water chemistry close: but a couple noob questions

[tmarks66]

Hi folks - my first post, so have mercy. Found this site a few weeks back after a couple trips to pool store gave no results when I found I could not keep any free chlorine in the pool this year (6th year). Like most of you, after seeing the amazing info on this site, I am a believer.

Situation: Using newly purchased TF-100 test kit, I discovered my CyA is high (85-95), and I had more CCs than desired. I have acquired lots of bleach and been adding this to the pool (almost) per SLAM process for the last couple of weeks. I say almost because I have not raised the FC level to the full shock level ( which would be ~ 35ppm at my CyA level). At most, I've been to 8ppm. I also have not brushed (vinyl) pool walls as they appear clean to the eye, and are not slimy to the touch. Bottom line - pool water seems to be in very good condition.

Results: Pool water is super clear. I have minimal (< 0.5 ppm) CCs. However, I lose about 2ppm of FC each night, so I'm not passing the OCLT test. I can maintain this condition by adding 1 gallon of bleach every other day or so.

Questions: Why do I lose the 2ppm overnight? How often/how much bleach should I expect to add on a regular basis to maintain proper FC level in my 22,000 gal vinyl pool?

Thanks for any help you can provide!

 

[duraleigh]

Welcome to the forum.

Why do I lose the 2ppm overnight?

You have organics still in your pool. You never SLAMmed the pool correctly to eliminate them. "almost slamming" might be in the same category as "almost pregnant"

Raise your FC to the SLAM level and keep it there and your OCLT will probably be succesful VERY quickly.

Of course, the better path is to drain/refill to get your CYA down to a manageable 40-50 and your FC levels can be maintained much lower.

 

[linen]

Welcome to tfp, tmarks66

duraleigh beat me but here are my comments...

Why do I lose the 2ppm overnight?

It means you still have organics (most likely algae) using up FC in your pool. Probably the best thing to do, is a partial drain/refill to lower your cya to ~50 ppm followed by the SLAM process:http://www.troublefreepool.com/pool-school/shocking_your_pool

How often/how much bleach should I expect to add on a regular basis to maintain proper FC level in my 22,000 gal vinyl pool?

1 gallon a day is a lot for your pool at that cya level...indicating just like the OCLT that you still have organics. Typical for a pool your size is more like 1/2 gallon per day (at ~50 ppm cya level)...but each pool is different.

 

[Bama Rambler]

Welcome to TFP.

I had this big long dissertation written and low and behold they both beat me to it. I'll just say Ditto what they said!

 

[ping]

Welcome to TFP tmarks66!

The others beat me to it, but I post anyways.

Chlorine is reduced by the sun and organics in the water. Since you have eliminated the sun when you did the OCLT, that means there are organics in the water that the chlorine is working on.

If the pool is properly balanced you should use 2-3 ppm of chlorine in a day for a typical pool. If you are losing more than that then there are organics and or the CYA level needs to be adjusted.

Post all of your test results and we can offer more suggestions on how to balance your water. It would be in your best interest to lower the CYA to 50, as it is much easier to SLAM the pool at that level. You also should be following all the details on how to SLAM in order to clear the pool properly. Brushing is required so any stuff on the walls will get exposed to the chlorine. The walls might seem to be algae free, but close observation they most likely have some organics that need to be brushed.

Have you learned how to use the Pool Calculator, http://www.poolcalculator.com/? Plug in your numbers and you will see that 22,000 gallons requires 66 ounces of 8.25% bleach for a raise of 2 ppm.

 

[tmarks66]

Thanks for the quick advice, guys! I believe I'll reduce my CyA first, and then do a true SLAM. I'll also brush. My next door neighbor's pool is low on CyA, and he lives slightly downhill from me. Maybe I can figure out a siphoning win-win here somehow! I have been recording my test data, and I'll post that once I get further down the lane on this process.

 

[AfterTen]

I can confirm "Almost" SLAM doesn't work. I "Almost" SLAMMED for a week with no change in OCLT number and my pool sounds a lot like yours.

For that week I did keep my pool at shock FC level. The water was crystal clear and my walls "looked" great. So, I didn't brush either. My CC during this week remained at 1 with minimal swimming during the week. But every morning my OCLT was showing a 4-6 ppm loss.

Well, I re-read the SLAM process and committed to it. Did a three time a day bleach addition (almost hourly on Sat. and Sun.) to make sure I stayed at or above SLAM FC and brushed twice a day.

Well, to my amazement ( ), 6 days later, CC is at or near zero and OCLT is well under 1 ppm.