The swamp of all swamps

[etbrown4]

We have a 25,000 gal Concrete pool in NC and the water is so dark green, it's borderline black!

Ordinarily we'd drain it, however the water table is within 1' of the surface, so that's not an option.

Here is the chemistry before we started last weekend.

Hardness 200-250, PH 8.4 !, Alk 120, CYA 120

Thus far 42 pounds of cal hypo has had little effect and we still can't see the bottom.

We'll be flocking today.

The plan is to vacuum to waste using the skimmer connection to clean the algae from the bottom, as there is no main drain on this pool.

Once we've vacuumed the bottom, we'll plan to drain down about 18" and refill to lower the cya.

We understand that the chlorine added has limited effect due to the cya. we have seen that chart.

Tips appreciated.

PS. We read somewhere that cya may typically reside on the top water surface. Anyone tested this idea to see if it is true? If so, possibly we should not pump from the bottom of the pool. It seems more likely that cya would be intermixed throughout the entire pool!

 

[frustratedpoolmom]

When you added 42 pounds of Cal Hypo - was the pump running? If so the theory of CYA on the bottom, etc is irrelevant.
18" won't lower it enough if the CYA is really 120 and how did you arrive at that number?

Tackle swampy swamps all the time - with the right test kit and the SLAM process it can be swimtime in a week!

CAM00043 by poolmom11, on Flickr
CAM00083 by poolmom11, on Flickr
CAM00123 by poolmom11, on Flickr

This pool is 12 ft deep and when I dropped my speedstir pill on the bottom I the water was so clear I could see it...

Oh and don't bother to flock.

 

[Casey]

You drop a hose in the deep end and add water while you use a sump pump to take water from the shallow end to address the high CYA. You need to get that down to better manage the SLAM or you're going to be buying a LOT of chlorine. STOP using Cal Hypo too. Don't waste your time or money on FLOCK. If you can sweep to waste, you can exchange water to lower your CYA.

 

[etbrown4]

Thanks for the feedback!

The last poster Casey, mentioned not using cal hypo. We used that so as not to raise the cya.
Curious what shock he would recommend. info much appreciated.

For frustratedMom,
Below is what we see for the Slam process on TFP, and it doesn't seem to mention a particular type of chlorine, unless we missed something
What kind do you use?
Nice pics! On the pool pictured it would be interesting to know the amount of chlorine added and the days it took to clear! many tkx

SLAM:
Measure the FC level
Add enough chlorine to bring FC up to shock level (or a little higher)
Repeat steps 1 and 2 as frequently as practical, but not more than once per hour, and not less than twice a day, until:
CC is 0.5 or lower;
You pass an OCLT (ie overnight FC loss test shows a loss of 1.0 ppm or less);
And the water is clear.
Chlorine additions should be frequent, especially at the beginning. Algae and other organic debris will consume chlorine very rapidly at first. As things progress, you will lose less chlorine each cycle and can add more less frequently.
Brush and or vacuum the entire pool once a day
Backwash or clean the filter as needed
Vacuum up debris as needed

 

[jblizzle]

We recommend almost exclusively to use liquid chlorine / bleach because there are not the same side-effects as the solid forms of chlorine.

How much Pool School have you read? Start with these:
ABCs of Water Chemistry
Recommended Pool Chemicals
How to Chlorinate Your Pool

 

[etbrown4]

Update.....

Using the Pool Math calculator in conjunction with the Cya/chlorine table, it looks like about 15 lbs of calhypo was all that should have been needed to achieve the cya/shock target of around 50 at this cya level!

Ok so we see that we've added triple the needed amount of calhypo. Hopefully that will burn off rapidly.

The ph reading is also suspect at 8.4 (previously a typo here) and will be retested.

While we got ahead of ourselves with the calhypo, it is hard to understand that interpolating the value from the cya/chlorine shock value, one would have thought that it would still begin clearing the pool. Perhaps since the cya is 20% above the high number in the table, the interpolation then perhaps should not be relied upon..

On the outer banks of NC you can't buy liquid shock except in gallons from Lowes or HD. No pool supplier sells it! It's all pucks and dry shock. period.

We' may want to go the liquid route eventually to keep the cya low, but for now it seems the battle is getting the cya down into the manageable range around 50 and then it seems for sure that the chlorine will then be able to to it's job!

For now the most helpful similar experiences if there are any out there, would be any with high cya like mine, as that seemingly changes everything.

Our next job is to get the cya down!

many thanks for any tips!

 

[jblizzle]

pH test is not valid when FC > 10ppm.

Most CYA tests stop at 100ppm. How did you get 120ppm? If it was a turbidity test, your CYA could be much higher. Dealing with this is certainly the first step.

You can shop at Walmart or equivalent and buy bleach instead ... same ingredient, slight weaker.

Did you add all that cal-hypo at once?
All of that has added between 100-150ppm of FC and 70-100 ppm of CH to your pool depending on the strength.
If you had a vinyl liner, they very likely would have damaged it ... we never recommend blindly adding chemicals like that.

 

[etbrown4]

cal hypo was added over 4 days. no more for now!

Right the fc has to be sky high, and we'll hope that will burn off quickly.

We got the cya 120 from strips and will be getting a more accurate tester.

 

[jblizzle]

By more accurate tester you mean one of the Recommended Test Kits ... right? ... right? ....

 

[etbrown4]

right!

also we tested the chemistry before shocking to establish a baseline.

 

[frustratedpoolmom]

That pool took 4 days to "clear" till I could see the bottom. The pool had ammonia, the first 4 hours I added chlorine every 20 minutes cuz it was consumed instantly, I went through 5 cases of 12.5% on the first day. It had a very powerful pump and excellent circulation so I was able to test frequently. The after pics are 7 days, I went back on day 7 and completed the final vac.

Do NOT trust CYA reading from strips. My unsolicited 2 cents...

 

[etbrown4]

How did ammonia get into the pool?

5 cases of 12% sounds like a lot but I guess that's 20 gallons.

I'll pass along today's result later on, but we have improving clarity after draining and refilling 20" or so.

 

[Casey]

The CYA is converted into ammonia by a bacteria. It's all a mystery but it happens in certain circumstances that no one really can lay their finger on. Sometimes people open to a crystal clear pool and add chlorine to find it's not holding. They start the SLAM and the CC's shoot way up. The pool just consumes wild amounts of chlorine until the ammonia is broken down and eliminated. It's a freaky pool thing... lol

 

[Beens]

Did you order a test kit yet? If you order from tftestkits.net you'll get it really quickly since he's located in NC too.

I'm in va beach and mine came quickly. Fyi, I ususlly buy my bleach at Walmart or target and just found out farm fresh sells it a little cheaper so I can also get it there. (8.25%)

 

[JesseWV]

Before you spend more money on chemicals that will likely be wasted, get a recommended test kit! You need to know how high your CYA is before you can even start. You will probably have to perform a diluted CYA test if your CYA is above 100. Once you figure that out you'll know how much water needs replaced. Then you can follow Casey's advice and get started.

So again:

1. Get a FAS-DPD testkit. (I recommend the TF-100 with the XL and SpeedStir options for your situation)
2. Test your CYA level following the Extended Test Kit Directions.
3. Use PoolMath to figure out how much water needs replaced to lower your CYA.
4. Replace water following Casey's advice. Some people have had success using a tarp to give some separation of new and old water.
5. Begin the SLAM Process

 

[etbrown4]

Update....

Drained 28" of water
Refilled
Vacuumed the green sludge from bottom and sides to waste
Fc is now 10
Water is clear
CYA is 40
Hardness is 400

It took 6 days, but would have gone faster if we had drained it down first!

Thanks so much to all for the tips!

 

[jblizzle]

You FC is too low and not at SLAM level for a CYA of 40.

 

[etbrown4]

We seem to now have a clear pool and pretty much balanced chems, except for the high Fc.

Not sure why FC of 10 isn't acceptable at this point, and for now, and why we can't let it drop to 3 or so over a few days, with no swimmer load.

Tips much appreciated!

 

[jblizzle]

Because you need to finish the SLAM process until you pass the 3 criteria to stop.

You just said you vacuumed green sludge, so clearly you still have algae.

 

[etbrown4]

We vacuumed the green sludge about 4 days ago.

The walls and bottom are clean and the water is clear.