Nitrates in pool

[newsaltwaterpool]

I have a 33,000 gallon salt water pool that keeps reading 0 for FAC/TAC. We just had the salt cell replaced since it had stopped working. I took a water sample to the local pool store and they told me the nitrates in my pool were at 5 which is borderline for problems. They told me I would need to drain my pool, which I do not want to do. They then told me that I could try adding Power Powder Plus - 1 lb - every other day for 3 - 4 weeks to see if that would eliminate the nitrates. My other levels are reading fine and the pool is crystal clear. Can anyone give me some feedback on what I should do?

THANKS!

ph - 7.6
TA - 120
CYA - pp
CH - 220
salt - 3000 (3.0)

[waterbear]

nitrates are algae food. The only way to get rid of them is by water replacement. There is some indication that very high chlorine levels (100 ppm or so) might reduce them. They are normally not much of a problem if you maintain proper FC level (which for a salt pool would be a minimum of 5% of your CYA).

What is your CYA? You posted pp which is not a reading. Also, what SWCG do you have?

Have you tried shocking the pool with bleach to see if the FC holds or not?

[newsaltwaterpool]

Sorry--my CYA is 99. I have a Jandy 1400 SWCG. My pool won't hold any chlorine, I added 1 lb of power powder plus (Leslies product) this evening and I will see if I get any chlorine reading in the morning. I really don't want to have to drain water from the pool and replace it since I am on a well for water, when we have filled the pool we have used a pool water company and hope to not have to incur that additional expense this season. Is a reading of 5 for nitrates really something that would cause a problem?

[PoolDoc]

I've asked about the nitrate lowering idea; it's news to me.

But, in general, high nitrates would not have any effect on your chlorine consumption, by themselves. Do you have algae?

Also "5" is not a reading; "5 ppm" is and so is "5 ppb".

Ben

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[waterbear]

with a CYA of 99 ppm keeping your FC at 5 or 6 ppm should insure that the nitrates are not a problem in terms of algae blooms (which are the only problem they might cause, btw.)

If you are not holding chlorine then you need to shock the pool (I would suggest using bleach -- or liquid pool chlorine if available in your area -- since it is what your SWCG produces) and get the FC up to about 25 ppm (which would be about 13 gallons of 6% laundry bleach--about 18 of the 96 oz jugs commonly found these days OR about 6.5 gallons of 12.5% liquid pool chlorine/shock or 8 gallons of 10% liqiud pool chlorine/shock. This should be enough to kill whatever is consuming your chlorine and your cell should be able to keep up with the chlorine generation again (assuming the system is working properly).
http://poolsolutions.com/gd/best-guess-swimming-pool-chlorine-chart.html

HOWEVER, before you shock please test the water with an OTO test kit (sold as the 2 ways chlorine/pH test kits that use liquid reagents and have a chlorine comparator with yellow color blocks)
Your pool store is most likely doing DPD testing for chlorine and DPD can bleach out at high FC levels (OTO does not but only tests total chlorine). If the sample you test stays colorless then you have confirmed that there is no chlorine in the water. if it turns yellow, orange, or bronw you have chlorine (high chloirne in fact) and the pool store test is bleaching out. Please post your results so we can take it from there.

Also, you might want to collect some water from the cell itself when it is on to make sure it is making chlorine. Test this water yourself with an OTO test kit (comparator has yellow color blocks). If it turns yellow, orange, or brown your cell is working and the shocking I suggested above should do the trick. If it stays colorless your salt system is not working and you need to call for service (it might not be the cell but the control unit.)

Finally, stop depending on pool store testing! Get yourself a Taylor K-2006 test kit and test your own water. You might also want to invest in a tube of Aquachek salt titrators (test strips) or a Taylor K-1766 salt test kit to keep tabs on your salt level.

[newsaltwaterpool]

I do not have algae, the nitrate reading is 5 ppm per the pool store.

My water is crystal clear, and was clear before I added the 1b of power powder plus.

When I checked the chlorine level this morning using a test strip the FC and Total Chlorine were both reading low at 0.5. The guys at the pool store told me that the nitrates in the pool were the likely cause of the water not holding chlorine. As I mentioned before I want to avoid having to drain my pool since I have a well I can't refill it using my water, I would need to incur the expense of having water trucked in.

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Thanks Waterbear! I just purchased 25lb of the granular shock, if I do need to shock the pool I would want to use this since I already have it and don't want to waste it. Both Leslies and Anthony and Sylvan (who built my pool) have told me I should use granular shock in my pool. I will go and purchase the test kits you mentioned and post the results when I have them--and wait to shock the pool until then as well!

[waterbear]

nitrates will not directly cause chlorine demand. If you have a nascent algae bloom that might. Exactly what is the ingredient in your granular shock. If it is dichlor return it. for every 10 ppm FC added it will also add 9 ppm of CYA and your CYA is high enough. If it is cal hypo it is ok to use but it will cause your calcium hardness to rise. Let us know the ingredients and concentration and we can tell you how much to add to get to 25 ppm FC.
As far as only using granular chloirne in yoru pool, hogwash! Sodium hypochlorite is what your SWCG produces so you are normally chlorinating with liquid chlorine and if you shock with the unit, also shocking with it! Your pool does not know the difference beween sodium hypochlorite produces in the salt cell or poured into the water from a jug. Also, if you are predissolving your powder shock (which you SHOULD be doing if it is cal hypo0 you are also putting sodium hypochlorite in the water.

Some test strips will bleach out at high FC levels because they use DPD for the reagent (for example, some of the LaMotte test strips). Get yourself a cheap 2 way chlorine/pH tester that uses liquid reagents and has yellow color blocks on the chlorine side of the tester and do the tests I suggested. It is for good reason to help determine the reason you have low chlorine readings. You can pick up such a tester at walmart, home depot, lowes, may ace hardware stores, or most pool stores for a few bucks. If they happen to have a Taylor K-1000 get that one, it's the best one made!

[waterbear]

OK. did a bit of checking. Leslie's Power Powder Plus is 65% cal hypo (they also make a stronger 73% cal hypo, Power Powder Pro). You will need to add 11 lbs all at one time to get the FC up to 25 ppm in a 33k gallon pool. Adding a pound at a time won't do anything at all except replace any chlorine burned off by the sun every day since it only adds about 2 ppm FC in a pool your size and 2 ppm FC per day is normal chlorine loss for most pools.

HOWEVER, as I said before, test with an OTO test kit to make sure that you REALLY have a chlorine demand issue (or possible SWCG malfunction) instead of the test just bleaching out and registering low when the chlorine is actually high. OTO does not bleach out, FAS-DPD can overcome bleachout up to about 50 ppm chlorine levels, Syringaldazine which is used in some test strips, also does not bleach out.
DPD, used in many test strips and most pool store testing liquid reagent test kits does bleach out at FC levels from 3 to 10 ppm, depending on how the strip or test kit is forumulated.

[newsaltwaterpool]

I tested with an OTO test kit and got a low reading of chlorine (0.5), but at least there was a reading.

I haven't added any power powder plus since Monday evening, I turned the SWCG on to 60% yesterday, so that means it is generating something, right? Do you think I should still go ahead and shock with 11lbs of power powder plus?

Forgot to mention, my pH was reading 8.0

[waterbear]

Did you test the water coming directly form the cell? (Turn off the system and loosen a union on the cell to collect the water from the side of the cell going back to the pool when the cell is on and generating.) The chlorine should be very high when tested with OTO--dark yellow to orange to brown color. This will insure that the SWCG is working properly. If not you should try cleaning the cell with acid as per your manufacturer's instructions.

In any case, drop your pH t0 around 7.6, shock the pool, and I believe that you will find that your chlorine will hold after that. You probably have a nascent algae bloom that is consuming the chlorine as fast as it is being produced and shocking will destroy it and allow the SWCG to catch up and maintain the pool (assuming the system is properly working, hence the test suggested above). With a CYA of basically 100 ppm you want to adjust the cell to maintain the FC at NO LOWER THAN 5 ppm. 6 ppm would be a comfortable level to aim for. Also, do not try and test pH until the FC level drops below 10 ppm after shocking. HIgh chlorine levels will cause a false high reading on pH tests.

[newsaltwaterpool]

OK--I shocked the pool last night with 11lbs of Power Powder Plus (65% cal hypo), this morning the pool is cloudy and there is white "dust" on the bottom of the pool. The FC is >8ppm and of course the pH is high at 8. I don't have any other readings at this time but I am concerned about the cloudy water and dust--what should I do, is this normal?

[waterbear]

You did predissolve the shock, didn't you? Also, you did drop the pH first like I said, correct? Most likely you precipitated out some carbonate (and lowered both your TA and CH in the process). This makes me suspect that your TA and CH were higher than you reported (and is a good reason to get a Taylor K-2006 and do you own testing rather than rely on the pool store!) THIS is also the reason I initially suggested using bleach, since it will not cloud a pool . It's not a big deal and it will filter out. Brushing will help. I would suggest getting your water tested (and ordering your own test kit).
Did you ever test the water from the cell to make sure it is working properly?

How are you testing the pH? Some pH tests will read high with FC above 3 ppm, another reason we like the Taylor kits. They are good to about 10 or 15 ppm. If you are SURE that the pH is 8.0 and not just an interference from the FC at 8 ppm or above (how was that measured?) then go ahead and add some acid to get the pH down to about 7.6.

[newsaltwaterpool]

Yes, I predissolved the shock and dropped the ph.

The dust seems to have cleared now but the pool is still cloudy. I just got the Taylor K-2006 test kit and here are my results:
FC - 3 ppm
CC - 0.5 ppm
pH - 7.6
TA - 160
CH - 380
CYA - <30
salt - 3100 (3.1)

[PoolDoc]

1. With a DE filter, the cloudiness should clear pretty quickly, if you leave your pump on continuously.

2. How much more cal hypo do you have on hand? Can you buy dichlor at Sams Club? (only local source for undiluted dichlor)

[newsaltwaterpool]

The filter is off for the night, should I turn it on and let it run overnight?

I have approx. 10lbs cal hypo on hand.

Thank you for all of the help I am getting, it is very much appreciated!

[waterbear]

Yes, I predissolved the shock and dropped the ph.

The dust seems to have cleared now but the pool is still cloudy. I just got the Taylor K-2006 test kit and here are my results:
FC - 3 ppm
CC - 0.5 ppm
pH - 7.6
TA - 160
CH - 380
CYA - <30
salt - 3100 (3.1)

OK, as I suspected, your TA and CH were much higher than originally reported by Leslie's testing. No big surprise here, which is why we stress testing your own water. Keep the pump running a the pool will clear soon. Your TA is still high for a salt pool but that can be dealt with later.
Right now you need to get some CYA in there ASAP. That is why you have not been holding chlorine. Period! Also, you have some CC left after the shocking so there was probably an algae bloom on the verge. I think I know where Ben is going with the dichlor question. The fastest way to get CYA in the water is to shock with dichlor since it is so fast dissolving and it adds .9 ppm CYA for every 10 ppm FC added. It wont' be enough by any means but it will be a start.

[newsaltwaterpool]

Do I need to do anything about the cc reading? What do you recommend using to raise CYA since I don't have dichlor?

[PoolDoc]

You need to purchase some plain stabilizer -- cyanuric acid. That is still usually sold unblended or diluted, but we are beginning to see problems there, as well, so pay attention to the label when you buy.

To get a 60 ppm increase in stabilizer, you need 15 lbs.
Here are links from Amazon:

Kem-Tek Stabilizer 4lbs (http://www.amazon.com/exec/obidos/ASIN/B000LNY2AU/poolbooks) - $4/lb - Aug 2012
Nava Stabilizer 4lbs (http://www.amazon.com/exec/obidos/ASIN/B003TXOTT8/poolbooks) - $3.70/lb - Aug 2012
Nava Stabilizer 8lbs (http://www.amazon.com/exec/obidos/ASIN/B003TXN9GW/poolbooks) - $4/lb - Aug 2012

And, Walmart links (buy locally, but you can check stock online):

Aqua Chem Stabilizer, 3lbs (http://www.walmart.com/ip/Aqua-Chemical-Stabilizer-3lbs/17126388) - Caution: price not listed.
HTH Stabilizer and Conditioner (www.walmart.com/ip/HTH-Stabilizer-and-Conditioner/17043638)
- listed at $16/lb!


Ironically, it's actually cheaper to buy dichlor, which is effectively 55% chlorine and 50% stabilizer (no, not a misprint -- a chemical oddity I'm not going to explain here) when you consider the value of both the chlorine and the stabilizer. And of course dichlor is much easier to use than the very slow to dissolve pure cyanuric acid.

24 lbs PoolBrand bagged shock (http://www.samsclub.com/sams/shop/product.jsp?productId=108822) @ Sams Club - ~$2.50lb - Aug 2012
Kem-Tek Dichlor 22 lbs (http://www.amazon.com/exec/obidos/ASIN/B0030BEHZA/poolbooks) @ Amazon - $3/lb - Aug 2012