Shocked and now chlorine is too high

[bpajax]

My daughter just moved into a new home with a 34,000 gallon pool here in Florida. It's marcite. The prior owner chlorinated with tablets and shocked with liquid chlorine ("when I got algae"). It looked great when we moved in, but a few days later, some algae began to appear. We tested and had some CC so we shocked (almost a week ago) with around 12 gallons of 10% chlorine. It cleared the algae and the pool looks great now. I was trying to make sure we hit "breakpoint" and I'm pretty sure we succeeded.

Here are our current readings:

Ph 7.4
TA 80
Cyan 100 (way too high for me - apparently due to prior owner's tablets)
FC - still very high at 25 plus (can't tell for sure using my Taylor test kit even when I dilute and multiply by 5)
Sand filter

My question is how low does the FC have to get to be safe to swim in? Per the chart here on the website, our target FC with 100 Cyan is 12. The sun has been beating on it since Saturday and it's still very high. Not sure how long to wait - or if we should drain some to get the stabilizer down and the chlorine too.

Thoughts?

Thanks much.

 

[jblizzle]

Welcome to TFP!!!

First, we NEVER recommend doing what you did by adding that much chlorine at once as it can cause damage. If you have algae, we teach to use the SLAM Process. In fact, I would suggest that you should still follow this process until you pass the 3 criteria to stop.

Second, you can not do the SLAM process without the recommended FAS-DPD chlorine test. It will read FC and CC up to 50ppm without having to try to dillute and do color matching. Get it here: FAS-DPD Chlorine Test

Third, the first step we would suggest is replacing a LOT of water to get that CYA back down into the recommended range of 30-50ppm. See http://www.troublefreepool.com/content/134-recommended-levels

The required FC level for maintenance and SLAMing is a function of your CYA level. In reality since your CYA is so high, your FC is actually not that bad. In fact if you look at the FC/CYA Chart, if your CYA was 100ppm, your FC level should be maintained around 12ppm at all times and for SLAMing you would need to hold the FC at 39ppm. Since you CYA is higher, the FC numbers would be higher also.

To answer you actual question, it is safe to swim up to SLAM level FC ... so if your FC is below 40ppm, you are certainly fine to swim.

Redo the CYA test starting with 50/50 mix of pool and tap water, then add the reagent, then read the test a few times with bright indirect light and the tube at your waist. Then double the reading to get a better idea of your CYA level.

 

[bpajax]

Thanks very much for the feedback. The CYA test was done at two different pool stores and one was 97 and one was 100. I definitely want to get the level down to below 50 so I guess I need to gradually start draining and refilling. I'd like to just do it and be done with it, but I don't think it's safe to take more than a foot or so of water out at a time for fear of the water table here in Florida popping it.

 

[jblizzle]

OH, I thought you did this testing. If you did not, then Step 0 is to order one of the Recommended Test Kits.

You are right that you need to be careful with draining too far.

 

[karmabiker]

Thanks very much for the feedback. The CYA test was done at two different pool stores and one was 97 and one was 100. I definitely want to get the level down to below 50 so I guess I need to gradually start draining and refilling. I'd like to just do it and be done with it, but I don't think it's safe to take more than a foot or so of water out at a time for fear of the water table here in Florida popping it.

Reality may be much much higher than that... definitely time for a TF-100 test kit. get a good set of numbers and we can help.

Welcome to the forum!

 

[Smykowski]

Reality may be much much higher than that... definitely time for a TF-100 test kit.

karma's right, which is why I want to highlight it. Most pool store cya tests (which seem to be notoriously unreliable) top out at 100. Even the good test kits that we use are only valid to 100. It is very likely that yours is way, way over 100, and there's no way to know how much. You can do a dilution with a Taylor test kit that will get you close, but I see multiple drains/refills in your future.

 

[bpajax]

So I want to start draining. The more I drain at once, the less "dilution" water I will have to add to get the CYA down, but it's not safe structurally to drain out too much. Any suggestions?

 

[Casey]

Drain a foot of water and refill it until you hit a reasonable CYA amount of 30-50PPM CYA. It could take several drain/refills and is much safer than just dumping the whole pool. You do NOT want it popping!

 

[bpajax]

Drain a foot of water and refill it until you hit a reasonable CYA amount of 30-50PPM CYA. It could take several drain/refills and is much safer than just dumping the whole pool. You do NOT want it popping!

Definitely don't want it popping. Our pool popped during construction 15 years ago. The pool contractor just about died. Fortunately it was covered by his insurance. They had to totally break up the pool shell and redo the entire pool.

 

[bpajax]

I'm going to drain some of the pool to get the CYA down. Does anyone know if the CYA is more concentrated at the top or bottom of the pool? I read elsewhere that if you let the pool sit for 8 hours with no circulation, that the CYA will rise to the top. You can then remove water via a sump pump or skimmer hose from the top of the pool and get a higher concentration in your removed water - thereby requiring less water be removed overall. Thoughts?

 

[jblizzle]

Not true. It is evenly distributed.

 

[Beens]

Have you ordered a test kit yet? *don't forget* You'll need it so you can test the CYA and more accurately test your FC level so you might as well get it on it's way.

 

[Isaac-1]

If your fill water is cooler than your pool water you can run a fill hose down to the deepest point of the pool while you drain from the skimmer / surface. This cooler CYA free fill water should sink and separate some from the pool water partly keeping it from high CYA water you are draining, and lower the dilution while you drain. This will not last long though, but may help a little.

Ike