Chemicals To Add To A Freshly Filled Pool?

[Schaef]

Okay, my TA and CYA were through the roof and my pool was looking like a pond so I did a full drain and power washed all the green algea out..... now its refilling (slowly ).... for a 10,000 gal pool what should I add right off the bat??

Thanks,

Jeff

[Schaef]

It's about 3ft down from full and still is distingtively green!!!!!!!!!! HELP HELP HELP ..... maybe I drain it again and just open it up as a skate park for the neighborhood kids?

[itabb]

I'm no expert, and I'm sure waterbear or chem geek will reply soon. You could add some polyquat 60 as you fill. This should kill alge in about 12 hours. I'm not sure if you can have the polyquat in there without the filter running, but I would imagine that with the fill water moving the water around a bit, you'd be ok until the pool is filled. I'm just not sure about the potential for staining.

Here's a quote from Waterbear, if you are considering this course of action:

Do NOT use anything but polyquat 60! Look for the ingredient poly[oxyethylene(dimethyliminio)ethylene-(dimethyliminio)ethylene dichloride] on the bottle and you have the right thing. Dose according to bottle directions and run the pump for 24 hours after adding.

I bet your high CYA is what caused your alge problem to begin with. Are you normally chlorinating with trichlor or dichlor?

Here is my experience with this. My pool turned green as well, but from a chlorine demand issue instead of a CYA issue.

[chem geek]

Right off the bat you should add chlorine. Get some bleach or chlorinating liquid into that pool water right away or else the algae will continue to grow. You may also need to increase alkalinity by adding sodium bicarbonate / baking soda / Alkalinity Up so that your pH is stable (get at least to a TA of 50 -- your fill water might already have high TA so you might not need to add any). With visible algae, it may take a LOT of chlorine -- just keep adding it to keep the chlorine level up around 15 ppm until the chlorine level holds overnight. 2.5 gallons of bleach would raise the FC by 15 ppm in 10,000 gallons so with your water at 3 feet below the top it would take less than half that, so add 1 gallon of 6% bleach right away. If you use 12.5% chlorinating liquid instead, use half the amount as you would for 6% bleach. Always add the bleach slowly, preferably over a return with the pump running. In your case with a partial fill, just slowly distribute it around and then try and mix the water with something, even a brush.

You might need to add some CYA, but I assume that you will likely have some residual CYA left in your pool from before. TO BE SAFE, test the CYA level first. If you don't measure any, then use about 10 ounces weight of Dichlor for your partially filled pool (this will result in a CYA of 13.6 ppm when the pool is filled completely). After you shock the water with chlorine and the chlorine level holds overnight, then see how it is during the day. If it is burning off very quickly, then you may need to add some CYA and the easiest way to do that is with some Dichlor which adds both chlorine and CYA, but of course you won't want to overuse it. For every 1 ppm FC added with Dichlor, you add 0.9 ppm CYA. If you have a good test kit, such as the Taylor K-2006, then you could explicitly test your pool water for CYA to see how much residual was left over from before.

You didn't say if your pool was vinyl or plaster/gunite. If the latter, then you also need to add calcium chloride. For the alkalinity and calcium, add amounts appropriate for the estimated amount of water you currently have filled. You'll add more later as it fills up more. Also, if your pool is vinyl, then you'll want to be more careful about adding the chlorine with an appropriate amount of CYA so test the CYA level first and use some Dichlor if there isn't measureable CYA. Even if you measure no CYA, do not use more than 80 ounces weight of Dichlor as that would add 30 ppm CYA to the pool. After all of your drain/refill work, you don't want to end up with too much CYA!

As itabb mentioned, you should not use Trichlor tabs/pucks as your sole source of chlorine unless you regularly drain/refill a part of your pool water. Do you have a cartridge filter? If you had a sand filter with regular backwashing then the dilution would slow down the rise in CYA over time and could get to a reasonable balance. You have several choices for ongoing maintenance:

1) Use bleach or chlorinating liquid as your main source of chlorine. This requires daily addition of chlorine unless you have a pool cover in which case you can usually add the chlorine 2-3 times per week.

2) Use Trichlor pucks/tabs plus a weekly dose of PolyQuat 60 algaecide.

3) Use Trichlor pucks/tabs but monitor the CYA level and do a partial drain/refill to keep the CYA lower (30-50 ppm).

4) Use Trichlor pucks/tabs and additional bleach or chlorinating liquid to maintain a higher FC level appropriate for the CYA level.

For options 1, 3 and 4, you should aim for a target FC that is [EDIT] 1/9th [END-EDIT] the amount of CYA (i.e. the ratio of CYA to FC is [EDIT] 8.8 [END-EDIT]). The minimum FC is [EDIT] 1/14th [END-EDIT] the amount of CYA (i.e. the ratio of CYA to FC is [EDIT] 13.7 [END-EDIT]) so you need to add more chlorine to get to a higher FC level to ensure it doesn't drop below this minimum amount by the next time you add more chlorine. For option 2, the algaecide will prevent algae (but is expensive) and your minimum FC level is 3 ppm regardless of CYA level up to around 100 or so. A CYA level above 100 ppm may harm plaster.

Richard

[itabb]

I'm a bit confused at your ratios. 1/14 sounds right for the minimum FC to CYA. 1/9 seems like the normal range to prevent alge without a SWG or Borax. You said that 1/9 is the minimum, but that's more than 1/14. Could you clarify?

[chem geek]

I had it backwards. Thanks for catching that error. I've edited the post accordingly. The minimum at 1/14th corresponds roughly to Ben's "Min" column (0.03 ppm disinfecting chlorine) while the 1/9th is a target in between the "Min" and "Max" column (0.05 ppm disinfecting chlorine).

[Schaef]

Thanks for your help - pool is gunite, filter is sand, no risidual CYA this afternoon's test confirms but my alk is high so the pool store says I need to add Muriatic acid..... this will also lower my pH right?? I remember reading something about areating (sp?) the pool water to lessen the effect on pH. Does that sound right??

[chem geek]

Thanks for your help - pool is gunite, filter is sand, no risidual CYA this afternoon's test confirms but my alk is high so the pool store says I need to add Muriatic acid..... this will also lower my pH right?? I remember reading something about areating (sp?) the pool water to lessen the effect on pH. Does that sound right??

OK, so with no residual CYA you do want to add some Dichlor as I suggested since that will give you both chlorine and some CYA. Just don't add too much and then you should switch to bleach or chlorinating liquid to keep the FC up. If you don't put in at least a little CYA, then the chlorine will get destroyed by sunlight too quickly (though right now it's going to get consumed pretty fast by the algae) and will be too strong. You can just add enough Dichlor to get to around 10 ppm CYA as I suggested.

As for the TA, do not worry about that now and you do not just add Muriatic Acid to lower it. Acid lowers both pH and TA. The only way to lower TA is through a combination of aeration and acid addition, preferably at low pH to make the process go quickly. You can certainly deal with that later after your pool is clear from algae. The process for lowering TA (when you get around to it) will be as follows (I've put this on other posts).

ACTIVITY .......... pH .... TA ... In your case (assuming 6.8 is the lowest measurement on the pH test kit)

==================

Acid ..................... - ........ - ... Add enough acid to bring pH down to 7.0 (if it's already there, then just skip to the next step, aeration)

Aeration ............. + ....... 0 ... Aerate until pH rises to 7.2

Acid ..................... - ........ - ... Add enough acid to bring pH down from 7.2 to 7.0 (you may continue to aerate while you do this)

-----------------------------------

Aeration & Acid .. 0 ....... - ... Continue this combination (cycling of the two above) until TA is at the target you want

then AFTER you have reached your target TA,

Aeration .............. + ....... 0 ... Aerate until the pH rises to your target pH (say, 7.5).

==================

Net of Above ....... 0 ........ -

Note that there is NO addition of base (Borax or otherwise) in the above procedure. Aeration would include running your SWG, running your waterfall, adding any fountains or other aeration features, getting an air compressor with a nozzle that produces tiny bubbles and putting that in the deep end of the pool, etc.

Hope that helps,

Richard

[Schaef]

okay - that sounds like a plan - I'm on it!

Thanks again for your time!!!!!!!

-Jeff