algae question

[vrolland]

Good afternoon

I have a green swamp. Not real bad, you can see the bottom in the shallow end. Before finding this site, over the winter I had dumped trichlor into the pool every month or so to try and keep the algae away. So now, I have my test kit and the CYA test is way over 100. Only got a half inch of drops in before the black dot disappeared.

I'm going to run it again, filtering the water through a coffee filter and letting the water get room temp. Right now it's 50 F.

Am I right to assume using trichlor has my CYA this high? And should I replace 25% of the water per The Pool Calculator?

Thanks for your help and this site!

 

[Bama Rambler]

I would begin with replacing half the water and refilling, then test again.
Once you have the cya down it'll be much easier shocking the pool.

 

[fast1971chevelle]

Have you performed the half pool water and half tap water cya test to get a more accurate reading on your cya? Take half pool water and half tap water and double the results then use that value with the pool calculator to see how much to drain......Mike

 

[vrolland]

Thanks bama rambler and mike. I wouldn't have thought of the half tap water idea. I appreciate it.

Can I assume your thinking is, the temperature doesn't affect it that much?

 

[Bama Rambler]

Cold temps don't affect the test very much and since you're reading over 100 ppm it's a safe bet to drain half and refill. At best you're still gonna be near 50 ppm and probably higher.

 

[vrolland]

well, i guess i'm ready to shock. Cya is 70, ph is 7.2 and alkalinity is 140. my pool calculator says the FC level I want for mustard algae is 29, and for shock is 16?

Before I start pouring in the chlorine, I want it to get to 29; is that right?

 

[jblizzle]

No.

I would recommend actually doing another 50% water change to get in the 30-50ppm range on CYA ... just makes the required FC levels lower.

You want to maintain the shock level for what ever your CYA level is. No need to go to the mustard shock level.

If you look at the chart in Pool School, you will see that the shock level for a CYA of 70ppm is 28 ppm. According to the poolcalculator, the shock level is 20ppm ... not sure how you got your numbers.

Either level will work, Pool School is a little more aggressive.

 

[vrolland]

I got that number from poolcalculator. It has four levels, the highest one called mustard algae shock.

That is not the one I want? I do have a green swamp.

 

[jblizzle]

You had to have had the CYA set to 50ppm and not 70ppm to get those numbers. Read these to learn the correct shock process:

Defeating Algae
Turning Your Green Swamp Back into a Sparkling Oasis
Shocking Your Pool

 

[Safetybob]

It may seem counter intuitive, but you will be helping yourself alot by getting that CYA level down to 30-50 as recommended above. It won't take alot of bleach to kill the rest of the algae you would have left then AND that lower CYA level will require less chlorine in the first place.....why not save some money and make the pool experience better for everyone?

Put the pucks away for when you need to raise CYA. I only "add" a puck when after proper testing, my pool tells me it needs CYA.

Was the swamp caused by a bunch of leaves and stuff falling into the pool? If so, it is possible to install a cover of some sort.....hopefully keeping pool better?

Bob E.

 

[vrolland]

I am seeing first hand that the cya level down to 30 -50 is almost a must. I dumped half my water, did the test again and the number didn't change. Maybe I had cya of 300, I don't know.
But I figured I had gotten half of it out. So poolcalc told me to put in 8 jugs of bleach, I did that, it put my chlorine level up to about 100 ppm, and it's pretty much stayed there all week, and we still got green.
High cya has to be keeping the chlorine from doing anything. Do you think the water is now too toxic to dump in the storm drain?

 

[RobbieH]

The FC should come down pretty quickly. How big is your pool?

 

[vrolland]

23000

 

[jblizzle]

How did the poolcalculator recommend adding 100 ppm of FC ???

Clearly something was not correct in your inputs.

You can try using 50% pool and 50% tap water to start the CYA test and then double the reading to get a better idea. If it is still around 100, you likely are about 200 ppm on CYA still.

 

[vrolland]

if you have a 23000 pool with zero fc and you want to raise it to 28, it says 1002 oz of 8% bleach, which is 7 gallons 3 quarts.

 

[jblizzle]

I agree that is what poolcalc, says, but up above you said the FC went to 100ppm, which is not possible if you added 8 gallons of 8% bleach ... it should have gone to 28ppm. Unless your pool is much smaller and/or the chlorine was much stronger and/or you added much more than 1000 oz and/or there was a testing error.

What size were the bottles that you added? I am not aware of any bottles that are actually 128 oz.

Did you use 2 scoops of the powder reagent due to the high FC levels?

 

[vrolland]

i'm estimating. i quit adding drops. the test water stayed solid pink after i added 140 drops, which would be 70 ppm, so i quit adding drops. figured i was wasting the testing supplies at that point.
what do you mean by using 2 scoops of powder?
also, is this too high a chlorine level to dump in the storm drain?

 

[jblizzle]

At high FC levels, sometimes you need 2 scoops instead of just 1, but if the sample turned pink with 1 scoop you are fine.

How much water are you using when doing the FC test? 10ml or 25ml? It just does not make sense that you FC could get that high.

The FC will quickly be consumed by any organics in the storm drain ... should be fine.

 

[Smykowski]

How fast are you doing the test? It needs to be controlled, but you have to move through it quickly, or it will never change to clear.