Phosphates eating up my chlorine?

[wposton84]

Thanks for the help Janet.

I had a feeling the pool store was attempting to sell me some snake oil, since I found no mention of phosphates anywhere in the information portion of this site, I figured it was a bunch of bull. Thanks for confirming my suspicions.

I live in Springfield, IL. The pool I am concerned about has nearly full sun from 10 am to 5 pm. I added 4 lbs of stabilizer a couple weeks ago (when CYA level was 15), not sure why the level did not increase more; perhaps the extra backwashing I have been doing has drained more water than usual and caused the level to drop. Also, the CYA readings I've quoted here are from the pool store's electronic test kit; I guess it shines a beam of light through the colored water to give a more "exact" reading and thats what it gave me. Using my Taylor kit, as you mentioned, I can only tell that the level is <30.

This may or may not help you diagnose my problem, but every year (for nearly 10 yrs), this pool seems to take several weeks before the water will clear and it will hold chlorine. Last Thursday, it appeared like that process was once again winding down since I could see the drain clearly and the chlorine was holding. I shocked it to clear out the last bits of cloudiness in the water, and figured it would be smooth sailing for the rest of the summer, as it usually is. Then today, the water had returned to the murky green swamp that it was when we started the year. Could this just be an algae bloom unrelated to the perennial problems I have clearing the water?

[aylad]

It is entirely possible that the backwashing you did actually washed out the CYA you added before it had a chance to completely dissolve, since it can take up to a week to fully dissolve and register in your water, and it is also probable that frequent backwashings have lowered your levels some. That may well be why you were having trouble holding chlorine in the water, especially coupled with an impending algae bloom that finally caught up with you.

What do you use for chlorination? If powder, is it cal-hypo or dichlor? Do you use pucks? I'm guessing it's cal-hypo by your reported Calcium level. Is your CYA typically high at the end of the season, and low or non existent at the beginning of the next season? If so, then the CYA is probably being biodegraded during the winter into ammonia, which can create quite a huge chlorine demand when the pool is first opened. Many of our posters here experience this, and for some reason it seems to be increasingly common over the past couple of years.

When you shock the pool, you need to get it up to the correct chlorine level and hold it there until the water clears, and until you're not losing any chlorine overnight--if you can test after sundown and again before the sun is on the pool and don't lose any chlorine during that time, then you're ready to let it drop back down. If you are losing chlorine overnight, then you know it's due to stuff in the pool needing to be killed and not due to the sun--so you keep that chlorine up until you don't lose any overnight.

So...in your case, I would get it back up to shock level (based on the CYA of 20 would be 12-15 ppm) and keep it there by testing and adding more chlorine as needed to get back up above 12 ppm, pump running 24/7 and backwashing filter as pressure indicates, until it clears. You might find it easier to use plain, unscented bleach for this purpose, which won't raise your calcium levels any higher. Once you get it cleared up, then I would test your pool a couple of times a day and see if the stabilizer just needs to be bumped up a little further to make sure you have adequate chlorine in the pool all day so you don't have another bloom. Most folks around this forum try to target 30-40 ppm or so, but I wouldn't worry about that until you get it cleared up.

Janet

[wposton84]

Janet, you absolutely rock, thank you so much for your quick and thoughtful responses.

For daily chlorination I use Tri-chlor pucks; cal-hypo for shock. It's interesting you mentioned the dramatic drop in CYA, last year everyone told me the problem was high CYA (and at 120 ppm, I would agree), but when I tested first thing in the spring, the level was almost nonexistent. I think you're theory about its bio-degradation into ammonia over the winter may be spot-on. I think I will continue shocking regularly until chlorine holds and water clears, then I'll add the conditioner.

I mentioned that I've had perennial problems with this pool, which would make perfect sense. I say that because up until last year I had been using a dichlor product to shock. My understanding is that the dichlor overstabilizes the water, which would leave more CYA to decompose over the winter. Then in the spring, when the CYA has turned to ammonia, the pool would require massive amounts of chlorine to clear the water. I would then use more dichlor shock to satisfy the pool's need for chlorine and eventually the water would clear. But the use of so much dichlor would raise the CYA level so high that it would set this whole cycle into motion again once the pool was closed in the fall. Is that a plausible explanation of what's going on?

[aylad]

Is that a plausible explanation of what's going on?

Absolutely!!! Don't know what your pool volume is, but I would highly encourage you to switch to bleach or liquid chlorine (if you can get it cheaper) to do your shocking, if not your regular chlorination. Plain, unscented houseshold generic bleach is what the majority of us use around this forum. While the cal-hypo breaks down into chlorine and calcium (fine until your calcium levels get too high, then you get milky water) and dichlor breaks down into chlorine and stabilizer (you've already seen the problems there), bleach breaks down into chlorine and salt water, both of which are welcome in the pool. If you'll post your pool volume, I can give you an idea of how much to use.....

And as far as your question about adding bleach to ammonia....I can't give you the chemistry behind it, except to say that it's not the same as adding straight bleach to straight ammonia. Don't know if the ammonia is different chemically than what we clean with, but I do know that in the water, there's no problem with it. My chemistry knowledge is really, really, really basic, although there are others here on the forum that can break that down for you if you really are interested,.......but make sure you're ready for a chemistry lesson!!

Janet

[wposton84]

It's approx. 25K gallons.

Any idea at what Calcium level I would begin to notice the water turning milky? (It's a vinyl liner pool, BTW)

[CarlD]

Of COURSE Jan rocks! (just ask her kids! )

Somewhere between 400 and 500ppm your water could go milky--if your T/A is high and your pH is a bit high.

If, for example, your T/A hits 200ppm and your CH hits 500ppm, your odds of a milky pool are good. But if your T/A is 180ppm and your CH is 400ppm, you will probably be OK.


If, however, your CH is in the 0 to 400 ppm range and your T/A is 125ppm or below, your odds of a cloudy pool from calcium is extremely low....any cloud is something else.

But with a T/A of 130 and CH of 230 you have NOTHING to worry about!

Carl

PS: Teenagers are here to keep us humble....

[wposton84]

I figured there wouldn't be any reaction b/t the bleach and ammonia, but it never hurts to double-check on something like that. I'm no chemgeek, either, but I would imagine there is just way too little bleach & ammonia and way too much water for any adverse reaction between them.

Thanks again for your help, this forum never disappoints.

[madwil]

the chlorine combines with ammonia- the CC reading when you test water...
then the extra chlorine and sunlight oxidize the CC away.
oversimplified, but that's the process in a nutshell!
So adding chlorine initially gives the CC, which smells and is irritating, then gets rid of it, along with sun and air!

[aylad]

In a 25K gallon pool, each 1/2 gallon of 6% bleach you add will raise your chlorine by just over 1 ppm, so each 2 gallons will raise it by approximately 5 ppm.... so you can use that as a guide when figuring out how much to add each time to get back up to your "shock" level. If you're using a drop-based OTO kit that only measures up to 5 ppm, you can use the directions here http://www.poolforum.com/pf2/showthr...a-good-testkit) to dilute your sample and at least give you a ballpark.

Janet

[wposton84]

Thanks for the info, Carl. Sounds like I can finish off the 25 lb bucket of cal-hypo that I've got without causing the water to turn milky, then switch to bleach.