fiberglass algae

[melgna]

I have an in ground fiberglass pool and I cant seem to keep the algae away.
I've spent hundreds of $$$$ this summer alone.
My levels are as of last week friday
FAC 0
PH 7.4
TA 140
Calcium hardness 250
CYA 100+
TDS 1100
Copper 0.3
I was told after this reading to add 2 bags of chlor brite and run the pump for 12 hrs.
Not much happened, I added 2 more bags on monday and another today.
still no improvement.
Any suggestions?????
I've been going through this cycle all summer.
Spend lots of money to get it crystal for one week, then green for three weeks.

[chem geek]

Absolutely unbelievable. You have well over 100 ppm Cyanuric Acid (CYA) and the store recommends that you add Leslie's Chlor Brite which is Dichlor. For every 1 ppm Free Chlorine (FC) added by this product, it also adds 0.9 ppm to CYA.

The reason you are always fighting algae is that your CYA level is way too high. You need to do a partial drain/refill to lower the CYA level and you need to stop using Trichlor pucks/tabs or Dichlor granular/powder for chlorine since both add to CYA. For every 1 ppm FC added by Trichlor, it also adds 0.6 ppm to CYA. Another granular chlorine product is Cal-Hypo and though it doesn't add to CYA, it does add to Calcium Hardness (CH). For every 1 ppm FC added by Cal-Hypo, it also adds 0.7 ppm to CH.

So what chlorine products do not add to CYA nor to CH? Unscented bleach, chlorinating liquid, and the very expensive Lithium hypochlorite. Those are what you should be using instead. The problem is that you need to add these every day or at least every other day unless you use a pool cover in which case you may be able to get by adding chlorine every 3-4 days. An automation option for bleach or chlorinating liquid is The Liquidator.

To get rid of the algae you have it will take a LOT of chlorine, so starting on the drain/refill will help. I would get bleach or chlorinating liquid and get your FC level up to at least 20 ppm while you are doing the drain/refill. That will at least keep the algae at bay. It would need a higher FC level to kill the algae quickly, but since you have to drain/refill anyway there's no sense in wasting that much chlorine.

There are other, more expensive, ways of dealing with the algae. One is to use a phosphate remover. Another is to add a copper algaecide, but that can cause staining and green hair at higher pH levels. A regular algaecide, such as PolyQuat 60, is best for maintenance, not for killing an existing bloom, because it's slow-acting. I am not recommending these alternatives, but do want you to know they exist. You can absolutely keep away algae with chlorine alone, but you need to not let the CYA level get too high. It takes a minimum FC level of 7.5% of the CYA level to keep away green algae in almost all pools (those with extraordinary phosphate levels above 4000 ppb need higher chlorine levels).

Richard

[melgna]

So I should not be using the chlor tabs in my floater?
Is bleach safe for my fiberglass pool?
If I'm using liquid bleach every 3-4 days how much should I use for
about a 20,000 gal pool and should I use anything else or preventatives?
Thanks for your help.

[chem geek]

My responses in bold below.

So I should not be using the chlor tabs in my floater?
You should absolutely not be using Trichlor tabs in your floater. Trichlor increases the Cyanuric Acid level and you already have way too much.

Is bleach safe for my fiberglass pool?
Absolutely. Bleach and chlorinating liquid and in fact ALL of the chlorine sources produce IDENTICAL chlorine in the water (hypochlorous acid and hypochlorite ion). The only difference is that some sources add extra chemicals -- the Trichlor tabs you put into the floater and the Dichlor "Chor Brite" shock both add Cyanuric Acid; Cal-Hypo adds to Calcium Hardness. Other differences are in the pH of the chlorine sources. When using the tabs (which are very acidic), you probably had to use pH Up to raise the pH. When you use bleach or chlorinating liquid, the pH would normally be fairly stable but your high TA level will have a tendency for the pH to rise so you'll be adding Muriatic Acid to compensate for that instead.

After your CYA level is lowered through dilution and your pool gets cleared up, you can lower the TA level which will help to stabilize the pH when using bleach or chlorinating liquid. And yes, this is the opposite of what pool stores say where they think that higher TA leads to greater pH stability, but they are wrong when not using acidic sources of chlorine -- TA itself contributes to rising pH due to outgassing of carbon dioxide. TA is a measure (mostly) of the carbonation of the water -- pools are intentionally over-carboanted, just like a beverage. That's why low pH and aeration work to force more carbon dioxide out of the water faster and that makes the pH rise (so adding acid then lowers both pH and TA) and is how the TA lowering procedure works here. pH Up is Sodium Carbonate while Alkalinity Up is Sodium Bicarbonate -- both increase the level of carbonates (which is dissolved carbon dioxide combined with water) in the water.

If I'm using liquid bleach every 3-4 days how much should I use for
about a 20,000 gal pool and should I use anything else or preventatives?
Unless you use a pool cover that keeps out the sun's UV rays or unless your pool is in partial shade, you will probably have to add chlorine every day or two. Bleach usually comes in 96 ounce (3/4 gallon) jugs and one of those with 6% unscented Clorox Regular will raise the Free Chlorine (FC) level by 2.3 ppm in 20,000 gallons (most off-brand unscented "Ultra" bleach is also 6%, though not marked as such -- so buyer beware). If you can get 12.5% chlorinating liquid from a pool store or hardware store at a decent price, then one gallon will raise the FC level by 6.25 ppm. Similarly, one gallon of 10% chlorinating liquid will raise the FC level by 5.0 ppm.

So comparably priced 12.5% chlorinating liquid for one gallon will be 2.7 times as expensive as a 96-ounce jug of 6% bleach. Comparably priced 10% chlorinating liquid for one gallon will be 2.16 times as expensive as a 96-ounce jug of 6% bleach. If you can find a pool store that sells chlorinating liquid and lets you return the gallon containers (often sold in a crate of 4) for exchange so that they refill them, then that is obviously better for the environment. The pool store I go to does that and I don't mind spending a little more for the chlorinating liquid -- it costs around $3.50 per gallon. That's comparable to about $1.30 for a 96-ounce bleach jug so isn't a terrible price (some people find that sized bleach on sale for $1).

If you have a pool cover, then the chlorine usage may be low at less than 1 ppm FC per day. Without a cover, you may lose up to half the FC amount on a strong sunny day at low CYA levels. With your current very high CYA level, then even without a pool cover the chlorine loss from sunlight might only be around 1/4 or less of the FC level.

Thanks for your help.
Your welcome.

You should also get yourself a good test kit. The Taylor K-2006 from Taylor here or from Leslie's here (NOTE: Leslie's stores may have the K-2005 which is NOT the same thing -- you want a FAS-DPD chlorine test so that you can easily measure chlorine levels up to 50 ppm -- standard kits only measure to 5 ppm) or from poolcenter(dot)com here the the even better TF100 test kit from tftestkits(dot)com here.

Richard

[melgna]

I was told that muriatic acid was not good for my fiberglass pool...???
I also have copper coming out of the water I'm putting back in and was also told to add metal free after replacing water.
Could this be affecting any of my levels as well?
I'll be drainning the pool tonight and I'll fill you in on the progress.
Aloha...

[chem geek]

Muriatic Acid is very strong and would not be good for pouring directly onto any pool surface. The important thing to do with any of the concentrated chemicals is to pour them very slowly over a return flow (arm outstretched) in the deep end so that the chemical mixes thoroughly with the bulk pool water.

Trichlor is VERY acidic and if the floating feeder were to park itself by the side of the pool and the pump was off, then acidity would build up near the feeder and harm the pool surface just as Muriatic Acid could if you poured quickly near the edge. In fact, I rusted some steel mounts holding stainless steel bars in my pool because of a floating feeder with Trichlor that parked itself near those mounts. That was the point at which I decided to learn about pool water chemistry (plus my CYA going well over 100 in less than a year and a half).

In any event, once your TA is lower you will not need to add acid very often. You can always pre-dilute it in a bucket of pool water and then slowly pour that over a return flow for extra safety.

I assume you mean there is copper in your fill water and yes, you will need to add a metal sequestrant for that. This is especially true when shocking with bleach or chlorinating liquid since that will make the pH rise and could precipitate metals if not properly sequestered. Before you shock, you can lower the pH down to 7.2 (using Muriatic Acid) which will help reduce how high the pH will go when you shock. As the chlorine gets used up, the pH will drop back down (that's why using hypochlorite sources of chlorine are really pH neutral when accounting for both addition AND usage of the chlorine).

Copper and "metal free" won't affect your other water parameter levels. In fact, copper is an algaecide so ironically having some copper in the water helps keep algae away while the "metal free" will remove some of this copper. The problem with copper is that it has to be carefully balanced to prevent precipitating out, staining and causing the water to turn green. The way to distinguish green water from copper vs. algae is that the copper green is more of a clear green instead of cloudy (though cloudiness can come from other problems such as high CH, TA and pH) and most importantly copper won't consume chlorine overnight while algae will (I say "overnight" because during the day sunlight breaks down chlorine).

If you are draining the pool, don't drain it too far down unless you are certain your water table is very low. Pools can pop out or move if drained too far (also, the pump is either turned off or the skimmer turned off assuming you have a floor drain). You can do continuous dilution filing at one end and draining from the other or can do multiple partial drain/refill cycles or can use the "sheet" or "silage bag" method to use less water. With the sheet or silage bag method, you fill water on top of the sheet or into the silage bag (that is floating in the pool) and remove water from under the sheet or outside the silage bag. The sheet or silage bag then drops into the water keeping the water level constant. When done, the sheet is removed or the silage bag turned over to empty its contents in the pool to mix the fresh and older water together.

Richard

[melgna]

Ok,
Drained the pool a couple of feet and three nights and 6 bottles of clorox and still just as green . No improvement.
I'm taking in a sample to get tested today. I'll get the numbers up when I get the results.