Fiberglass poll algae and alkalinity ???

[karenib]

We have a new pool and it has been sparkling until we got home from vacation 2 weeks ago. It was very green then. After the first week I managed to clear it up with chlorine(keeping it high 5ish), the PH (7.5ish) and alkalinity (80) were stable the whole time.

This week there have been blooms of algae and the ph dropped to below 7 the chlorine was still at 5. I got the ph up with baking soda, but the green on the walls and step kept coming back.
BTW, I live in Tampa so we get heavy rains every few days so I have had to also drain water at least twice since this started.Yesterday I took the water into the pool store to get help.

My numbers were FC 5, TAC 5, ph 7.2, TA 90, hardness 200, CYA 100. The guy there said that my alkalinity should be 100-120 and the ph should come up, everything else was ok.He gave us algaecide and told us to add it the day after we added the alkalinity up. He also said the ph would drop after adding the alkalinity up so I should add 8 oz of baking soda after a few hours of adding Alk-up.

We added 5 lbs of alkalinity up. This morning my numbers are chlorine 5, ph 7.8, and alkalinity 100, and the algae is gone. So why do I still feel like something is not right, lol.

I have my auto-chlorinator set at 4 the high is 5, should I keep it that way or turn it back to 3.5 as recommended by the installer? I use 3 inch pucks. The pool is 17,000 gallons and is in the sun all day.

So my questions are:

Is it true that alkalinity for a fiberglass pool should be 100-120?

Should I bother adding the algaecide since there is no algae?

Should I work (add chemicals) to get my ph lower or just check and see if it comes down by itself?

Should I be worried about CYA being 100?

Should I keep the auto chlorinator at 4 or should it be lower?

Thanks for any help!

[waterbear]

We have a new pool and it has been sparkling until we got home from vacation 2 weeks ago. It was very green then. After the first week I managed to clear it up with chlorine(keeping it high 5ish), the PH (7.5ish) and alkalinity (80) were stable the whole time.

This week there have been blooms of algae and the ph dropped to below 7 the chlorine was still at 5. I got the ph up with baking soda, but the green on the walls and step kept coming back.
BTW, I live in Tampa so we get heavy rains every few days so I have had to also drain water at least twice since this started.Yesterday I took the water into the pool store to get help.

My numbers were FC 5, TAC 5, ph 7.2, TA 90, hardness 200, CYA 100. The guy there said that my alkalinity should be 100-120 and the ph should come up, everything else was ok.He gave us algaecide and told us to add it the day after we added the alkalinity up. He also said the ph would drop after adding the alkalinity up so I should add 8 oz of baking soda after a few hours of adding Alk-up.
He gave you wrong advice. Alkalinity increaser is sodium bicarbonate, also called baking soda. It will increase TA and will cause a slight pH rise also. it will NOT cause the pH to drop!
We added 5 lbs of alkalinity up. This morning my numbers are chlorine 5, ph 7.8, and alkalinity 100, and the algae is gone. So why do I still feel like something is not right, lol.

I have my auto-chlorinator set at 4 the high is 5, should I keep it that way or turn it back to 3.5 as recommended by the installer? I use 3 inch pucks. The pool is 17,000 gallons and is in the sun all day.
What kind of filter do you have? If you have a cartridge filter you are going to have a very high CYa level very quickly and a lot of problems!
So my questions are:

Is it true that alkalinity for a fiberglass pool should be 100-120?
The alkalinity is not so much a function of what the pool surface is but of whether you are using stabilzied or unstabilized chlorine. Stablilizied chlorine (trichlor and dichlor) is acidic and the higher TA of 100-120 will help give better pH stability. If you are using an unstabilized chlorine you will get better pH stability running the TA lower (around 80 ppm)

Should I bother adding the algaecide since there is no algae?

Should I work (add chemicals) to get my ph lower or just check and see if it comes down by itself?

Should I be worried about CYA being 100?
Yes, It should be between 30-50 ppm!
Should I keep the auto chlorinator at 4 or should it be lower?
With a CYA of 100 ppm you need to maintain a FC of at least 8 ppm fo normal chlorination and need to shock to 25 ppm. You cannot achieve this level of chlorination with a trichlor feeder without sending the CYA levels even higher! You need to start using an unstabilized chlorine source for chlorination which cannot be used in your feeder!
Thanks for any help!

Hope this helps.

[aylad]

Waterbear's got it covered. The only thing I would add is that you need to stay away from that pool store--they obviously don't have a clue what they're doing when it comes to water chemistry. If you buy anything else from there, it should be a good drop-based test kit so that you can do your own testing. Believe me, you'll be saving yourself a fortune.

Janet

[Sprocket]

Yes stop using your auto CL and tabs , they raise your CYA .

Buy Ultra Bleach , I found Axis brand at Save a Lot stores for 1.18 3/4 gal , and use that . My CYA is 30ish and no problems with algae .

If you want to see all my "old" problems like yours , just do a seach using my name here on this BB board .

Tabs or Pucks raise you CYA and give you countless headaches with "the green stuff" .

[karenib]

Thanks everyone. I will be switching to liquid bleach.. I am going to Sam's club tomorrow and will see what deal they have there. Is there a difference between the chlorine in "clorox" and the chlorine they have at the pool store?

What test kit would you recommend and where is the best place to buy?

and finally, with CYA level so high, what should I keep my chlorine level at until CYA drops (I am hoping with all the rain in Aug that it will flush some out.)

once again thank for the advice

[CarlD]

OK,
With bleach, you look for the % on the label. Regular bleach is 5.25%, ultra is 6%. But now there are some "economy" types that are 3%--ultimately they cost more for the actual bleach than 6%.

Chlorox now has a added whitening agent which may or may not be good for pools--the jury's still out. In the meantime, generic bleach is better.

There are 3 test kits that will serve your purposes. All are basically the same and it doesn't matter really which you get. All use a chlorine test called FAS-DPD, which is NOT the same as the chlorine test called DPD.

1) Taylor brand K-2006 or K-2006C from Taylortechnologies.com
Taylor makes the chems that most of the better kits use. The C has more of each chem, but costs more.

2) Leslie's Pools Online (not their retail stores)--their FAS-DPD Chlorine Service Test Kit. Leslies test kits are ALL re-branded Taylor kits.

3) Troublefreepools.com. I don't know a lot about these kits other than they are similar in concept to the kits that used to be sold at our sister site Poolsolutions.com--the PS-234 (no longer available) What I do know about TFP kits is they use FAS-DPD for chlorine testing and have a complete suite of tests as the others do.

In a pinch, your local Wal-Mart may have an HTH 5-way Pool Test Kit that uses drop-testing, not strips. This will only measure chlorine via the OTO test to 5ppm, but diluting pool water with distilled water can extend the range. It's a lot cheaper but much more limited. Still, it's a bargain at $12 to $15 and far better than most of the other kits out there--and better than strips.

Search our site for the "Best Guess Table" -- it's stickied. It will show you the FULL range of CYA to FC levels. For a CYA of 100ppm, FC should normally be no lower than 8 and no higher than 15ppm. To shock, raise FC to 25ppm.

Dilution (such as rain) will help lower your CYA, but if you replace 25% of your water, you CYA will STILL be 75ppm.

[waterbear]

There are 3 test kits that will serve your purposes. All are basically the same and it doesn't matter really which you get. All use a chlorine test called FAS-DPD, which is NOT the same as the chlorine test called DPD.

1) Taylor brand K-2006 or K-2006C from Taylortechnologies.com
Taylor makes the chems that most of the better kits use. The C has more of each chem, but costs more.

2) Leslie's Pools Online (not their retail stores)--their FAS-DPD Chlorine Service Test Kit. Leslies test kits are ALL re-branded Taylor kits.

3) Troublefreepools.com. I don't know a lot about these kits other than they are similar in concept to the kits that used to be sold at our sister site Poolsolutions.com--the PS-234 (no longer available) What I do know about TFP kits is they use FAS-DPD for chlorine testing and have a complete suite of tests as the others do.

The Troublefree Pools test kit uses all Taylor reagents, does not include the acid and base demand tests of the Taylor K-2006 but does include a Taylor K-1000 OTO/pH tester for daily checks of pH and chlorine. It also includes more CYA reagent then the Taylor kit. It basically includes all the tests that were included in the PS-234 but the reagents are all Taylor reagents (I believe that some of the reagents in the PS-234 did not come from Taylor, but from another source.)