Adding bleach to fight algae without knowing the exact chlorine and stabilizer levels

Hello all,

My pool had been sparkling clear for the last three years, and I had my water tested by a local pool store. Upon coming back from a week-long vacation last month, I found my pump motor was not running. I had no idea when it stopped working. I took it to a local pool store, and was told that a capacitor needed to be replaced. It took a week for the part to arrive, and I had no water circulation during that whole week plus the unknown number of days since the motor stopped working.

Due to extreme heat in South Texas recently, I became lazy and did not test my water for that whole period of time. I just put three chlorine tablets in the floating chlorinator every week. By the time I got my filter system up and running again, the water already turned green. I did have problem with algae a couple of times in the past after hurricane Ike and a few big rain storms, but it went away after I shocked my pool a few times and increased the number of chlorine tablets used per week. The problem persists this time though, and my pool water has turned deep green after three weeks of treatment with high chlorine level. Since the pool store cannot accurately measure high level of chlorine, I have not had them test my water. Thus, I have no idea how high my chlorine level is.

A Google search brought me to this forum, and I learned the importance of knowing one's pool water chemistry to effectively combat algae. I've already ordered the K-2006C kit from Amazon, but it will take a few more days before it arrives. I bought a basic test kit (OTO) for pH and chlorine from Wal-mart to test my water in the mean time. The kit shows that pH is around 7.8. The chlorine test solution turns orange so I know it's high, but I don't know exactly how high.

I'd like to know if I can continue to add chlorine (I bough six bottles of 182 oz Ultra bleach from Costco for $2.77 each) without knowing exactly how high it is until the K-2006C kit arrives. Is it bad if I add too much chlorine and does not know the stabilizer level? My pool has never looked this bad before. Please help!!!

Be careful that the Ultra bleach is nothing but sodium hypochlorite!

Regarding chlorine levels . . . if you've got a concrete pool, go ahead and put it all in. But, hold off if your pool is vinyl or fiberglass. "Orange" is already high enough, till you know your CYA level.

Instead, work on lowering your pH. BUT, to be sure of an accurate test, you must dilute your pool water 50:50 with distilled (not: bottled, spring, crystal spring, super pure or ANYTHING except distilled!) before testing. Distilled water won't change the pH much, but will dilute the chlorine that otherwise could convert phenol red in to chloro-phenol red, a different indicator.

I received the K-2006C test kit yesterday evening after coming home from work. I tested my pool water right away, and the results did not look good: pH = 8, FC = 25; CC = 0.5, CYA > 200, TA = 250, CH = 380. I added 1 gal of muriatic acid and 182 oz of %6 bleach at 8 PM yesterday. I test again at 7:30 AM this morning, and the results were as followed: pH = 7.4, FC = 27, CC = 0.5. I added another 182 oz bottle of %6 bleach before going to work. My pool water is still deep green, and there are yellow/brown fine dust on the bottom. In the shallower end of the pool, I can tell the wall is slightly greenish/yellowish, but the water is so green in deeper end of the pool that I cannot tell if there is any algae growing on the wall. I've been brushing the pool every 2-3 days and cleaning the filter cartridge every week.

For the last four weeks, I've used about 20 tri-chlor tablets and 12 lbs of di-chlor granules to combat algea growth, and I guess that explains why the CYA level is so high. I have diluted water sample with distilled water (1:1), but the level is still higher than 100. That's why I list CYA level > 200 in the results above. I've also discovered another potential problem with the new tri-chlor pucks that I started to use two weeks ago (I've used about 8 pucks so far). Heeding the advice from this forum, I read the label and find out it contain 2.5% copper. The previous bucket that I just used up only contains tri-chlor. Could copper be the reason why my water is so green?

Here is some background information on my pool. It has an irregular oval shape (like a number 8 with one end smaller and shallower than the other end), with plaster wall. Filtration system consists of a Pentair Clean and Clear 200 (200 sq ft) cartridge filter coupled with a Purex Triton Ultraflow pump. The original pump motor died three years ago, and I replaced it with an Emerson EB841 1HP motor. There is a Nature2 Professional G system installed but I have never replaced the cartridge inside, which is a 35G model rated for pool from 25000-35000 gal. The pool came with the house when I purchased it in 2006, so I do not know the exact volume (I should have asked the previous owner ), but I have always guesstimated it at 20000 gal based on my rough calculation. The Nature2 vessel has developed a crack, which is a source of water leak that lowered the water level too much (below the skimmer intake opening) and caused the pump to stop working while I was on vacation.

I initially used a pool cleaning company to maintain the pool when I first purchased the house. For the past three years, I've been using a local pool store to test my water and add chemicals based on their recommendations. I've been using tri-chlor pucks in a floating chlorinator (2-3 tablets per week during summertime and 1 tablet per week during wintertime), and shocking the pool with di-chlor granules (2 bags per week during summertime, 2 bags once or twice a month during wintertime. I live west of Houston, Texas, so chemical loss is a big problem during the summer, especial this year. About three years ago, the pH level of my pool started to jump up to 8.0-8.4 (from 7.6 for the previous three years). I been adding a gallon of muriatic acid every week (sometimes 2 gallons) since then trying unsuccessfully to bring the pH level down. It seems like a losing battle and I think I've just discovered the reason why. I test my tap water yesterday with the K-2006C kit and the results were shocking to me: pH = 8, FC = 1.6. I've always smelled chlorine from my tap water, but I've never tested it until now.

I'm sorry for the long post, but I think the more information I give the better. I know I have a big mess to clean up and I really need all the help I can get. Your advice is greatly appreciated.

TIA

Look around in the pool stores nearby, and see if you can find any products by United Chemical, like "Yellow Treat" or "No-Mor Problems". These contain sodium bromide. Chlorine converts bromide to bromine, which is NOT affected by stabilizer. Adding bromide to a high chlorine, very high stabilizer pool like yours results in a small FREE and UNstabilized bromine residual.

There's a down side to this, explained here: once-a-bromine-pool-always-a-bromine-pool.html. But, since you may have to drain your pool anyhow, that's not such a big deal.

Anyhow, see if you can find some bromide based product. If you can, add 1/2 the recommended dose -- you can always add more, but you can't take it away. And, with 1/2 dose, you may not have high chlorine loss after the algae is gone. But, since the alternative is to drain and refill, so you can lower your CYA, there's really not much risk anyhow. If you get too much bromine in the pool, you just have to do what you'd have to do already, because of the super high CYA.

The other alternative is to take your chlorine up to 50+! This 'breaks' your pH test, and means you may have VERY high chlorine levels for a VERY long time after the algae is gone.

I'd start with the 1/2 dose of bromide.

Also, if you can, take the Nature2 out, and simply replace it with pipe.

Other points:
+ copper doesn't usually lead to green water, ESPECIALLY when the chlorine and pH are high!
+ high pH in your fill water doesn't necessarily mean high pH in the pool. Check the fill water's alkalinity: if that's high -- regardless of pH -- your pool's pH will tend to be high.

Thank you for your advice. I have another question though. According to the article in your link:

"If bromine has NEVER been added to an outdoor pools in the form of tabs, shocking the pool (5+ppm of chlorine in a single dose), added on sunny days, will tend to remove the bromine/bromide. However, repeated doses may be needed."

Since "Yellow Treat" or "No-Mor Problems" are not bromine tablets, does it mean that I don't have to drain the pool later to get rid of the bromide?

Thanks again!

The important difference between bromine tabs and bromide products is not the bromine vs bromide factor, but the presence of hydantoin in the tabs, which combines with bromine to allow solid bromine tabs, in a manner similar to the way that cyanuric acid allows solid chlorine tabs.

For reasons I don't understand, hydantoin apparently prevents the conversion of bromide to bromate, a process which is the 'exit door' for the endless "bromide + chlorine => bromine => bromine + dirt => bromide => restart" process.

However, your final statement that you may not have to drain the pool, if you use bromide products instead of bromine tabs is correct, I believe.

I decided to completely drain and refill my pool this past weekend to get rid off the algae bloom and the super high CYA level altogether. My pool is being refilled at the moment. I added 1 lb of di-chlor granules after I got about 100 gallons of water in the pool to ensure that algae would not start to grow again. Is there any potential problem with what I did?

You also mentioned that pool water pH tend to be high if the alkalinity of the fill water is high. The TA of my tap water is 220. Is that why my pool water pH tend to drift upward (>8.2)? Should I try to add muriatic every week to bring it down to the 7.4-7.8 range, or should I not fight it and just operate my pool at its "natural" pH as advised in one of your guides?

Thank you!

220 PPM is probably going to drift too high. You really don't want to have your pool go above 7.8 because won't be able to tell the difference between 8 -- which would probably be OK -- and 9 -- which would NOT be OK. So your upper limit on pH is partly based on testing capability rather than pool chemistry.

If you add acid WHILE you fill, and let the hose splatter into the water, instead of having the hose end IN the water, you'll aerate quite a bit of the TA away. Just make sure you DO mix the acid in the pool carefully, with the hose, and do NOT get the pH much below 7.0.

1# of dichlor is too much for 100 gallons of water (about 700 ppm of chlorine). That won't hurt a concrete pool, but if you've got vinyl pool, you may get some bleaching of the color. However, if the sunlight doesn't remove the chlorine immediately, you can be pretty sure anything that water touched is algae free.