Water improvement process has stalled - could CYA be too high to SLAM?

[dcb98f]

Hello,

We are new to pool ownership and had the pool opened 12 days ago. The water was very dark green and full of algae when we started, and after just a day it improved a lot to a blue green color. It has only improved marginally since then. We can see the bottom step, but still can't clearly make out the bottom of the pool.

I have backwashed the filter 3 times now, brushing daily, robot use regular, pump has been running 24/7, was at about 3300 RPM until today, I backed it down to 2600.

In the first 3 days, before I had fully read and understood the SLAM process, I had the pool store test the water and they suggested that we add the conditioner to it, which we did.

Now the CYA is over 100, which I don't think is a problem by itself, but doesn't that high of a CYA level require FC to be about 40 ppm to SLAM? I don't know of a reliable way to test FC that high yet, is there a way? One solution I can think of to lower the CYA would be to pump out about half the pool and refill with fresh water (I would pump and fill simultaneously), but I am hoping there is a better way. Do I just keep shocking it at like 1-2 lbs a day (dichlor granules)? I am a bit reluctant to go that route because if I can't test the FC at a high level I don't want to just waste expensive shock hoping for it to work.

Just tested the water
FC - over 10, results were very purple
PH 7.4
Alkalinity - 100
CYA - over 100 (pool store tested yesterday and it came back 106)

Thank you for reading and helping out a new pool owner.

 

[MITBeta]

To properly solve the problem of a green pool, you first need a reliable test kit of your own. The best one is TF-100 Pro with the stirrer. See Test Kits Compared.

Next use PoolMath to figure out how to add 5ppm per day of Free Chlorine to your pool while you are waiting for the kit to arrive. Stop using dichlor as this is contributing to your high CYA level.

When your kit arrives, post up a full set of tests, and prepare to perform the SLAM Process°

 

[Donldson]

First, welcome to TFP!

Do I just keep shocking it at like 1-2 lbs a day (dichlor granules)?

Dichlor is the absolute worst thing to use at this moment as it adds nearly as much CYA to the water as it does chlorine. If you've been using that in addition to adding stabilizer to the water then your CYA may be well over 100 and you're going to have to a pretty big drain and refill process. The SLAM Process specifies liquid chlorine as it doesn't add anything to the water except chlorine and some salt.

If you have the k-2005 then you're most of the way to having an adequate kit, but the DPD chlorine test it comes with is inadequate. You need an FAS-DPD chlorine test to bring it up to spec, and you can get it by itself instead of investing in a complete new kit. FAS/DPD Chlorine Test Kit

For now though you're going to want to get a grasp on just how high your CYA is. You can do an extended CYA test by mixing 50% pool water and 50% tap water, then using that to perform the CYA test and multiplying the results by 2. That will give you an idea, but if you already know your CYA is over 100 then a partial drain and refill is going to be necessary. It's just a matter of how big. Also remember that in a vinyl liner pool you need to leave at least 1 foot of water in the shallow end to keep the liner from shifting. So depending on how your pool is set up and how high your CYA is it might require a few incremental refills. If that's the case you may want to get a refill of CYA reagent too since you're going to have to test it a few times to get it right.

You're in the right place. It's going to take some work to get everything in line but once you do and you start to pick up on the what's and why's of TFPC it really does produce one of the best water experiences a pool can have. It's well worth the effort!

 

[reggiehammond]

As said above, get a proper test kit. Test Kits Compared

But with CYA higher than ~50-60, I can't recall a single successful SLAM ever reported. The cost of liquid chlorine will be exorbitant and it'll be difficult to find the quantity you need.

Be wise - replace enough water to get down to CYA ~30 and live to fight another day.

Read up on the wiki.

Draining - Further Reading

www.troublefreepool.com

 

[dcb98f]

Wow, thank you everyone for the responses. I already ordered the FAS/DPD test kit. I guess now it's time to bite the bullet and dilute this pool with some fresh water. I think that's my best bet at this point. Thanks again!

 

[reggiehammond]

Very wise choice. The only tricky part of a water replacement is to make sure you get to where you need to go on the first shot. You don't want to mix a bunch of new water into bad water and then have to go it again once it's diluted. So be aggressive - it's much easier to add a little CYA, etc than to fight water that's almost "good."

 

[dcb98f]

Thanks everyone for the advice. If anyone is still following, the results don't appear to be great so far judging by my new CYA level. I think I'm still around 80, somehow, not sure how that is even possible though. Unless I was way over 100 to start, which could be because the dot disappeared for me way under the 100 mark, and who knows how exact the pool store readings were.

The hard part about getting right the first time is we can only drain out about 1,600 Gallons before we have to start the simultaneous pump/refill process. We did that for 2 hrs, so if the rate on the pump box is accurate, we pumped and refilled 4,000 gallons, so a total of 5,600ish was pumped out and refilled, but a large portion of that could have been diluted I guess. Oh yeah, then Tuesday morning I did the 1,600 gallon drain and refill again, just for the heck of it, because I knew I was at work anyway, so why not, just had the wife watch the hose and water level during the refill.

But now we have pump problems, so that dominated my time yesterday, so my new cya reading was just to get an idea, I didn't have a lot of time to really test all the levels and dig into the results.

We also did an OCLT with the new test kit, and didn't lose any FC overnight (7 ppm in both readings), the water does look a bit better than before the drain, but I'm wondering if our chlorine is possibly locked up by the cya still. The CC went from 1 down to 0.5 overnight. Or maybe thats the chlorine loss? I still have to learn exactly what the results of the OCLT mean.

 

[reggiehammond]

Why only 1,600 gallons? If not draining more water, you should be doing a no-drain water exchange detailed in the Draining wiki.

The problem with your method is that your new water is diluting your old water, not replacing it. We want to replace it, new water in, bad water out.

7ppm FC is minimum for your CYA level, so you're not gaining any ground on algae, but also not losing much ground.

Is your pool in sun a good portion of day? If so - your CC really should be 0. Anything higher is evidence of the organics growing.

 

[dcb98f]

1600 gallons drains it down to where there is is still a few inches of water on the sun ledge thing, or shallow end. When our pool guy closed the pool down last fall thats as low as he wanted to go so there was still water on that ledge. I didn't think it would be good to go lower than that. If I post a pic of the pool would you be able to tell if it's safe to drain below that?

And yes, it's pretty much full sun on the west side of the house, pretty much all day.

 

[dcb98f]

After reading the draining wiki and doing that math, it seems very similar to what I did. Pumped from the deep part and put the fill hose as far away in the shallow end as I could, matched the flow/refill rate almost exactly.

I did an actual fill rate test with the hose this morning, and I think the main issue was that my pump/flow rate was closer to 300 GPH, not 2,000. After doing that math the drop to 80 cya makes a lot more sense. Updated math leads me to think that we need to do the drain/fill process for closer to 12 hrs, after doing the 1,600 gal. initial drain, not 2 hrs.

Hopefully that gets us down to around 40 cya, but the mixing aspect of it makes it a bit unpredictable.