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-gue...ine-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.