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Thread: Drain for Nitrates?

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    Drain for Nitrates?

    I have an in ground gunnite/concrete 32000 gallon pool in Maryland. Could not keep chlorine in. Treated for phosphates and confirmed they were gone. Had nitrate level of 15ppm. Pool store said that was causing the problem and I would have to drain and replace about 5-6 inches of water. The pool water people said I would have to drain 1/2 of the pool. Then I found your site and followed the instructions for "slamming" your pool with liquid chlorine. I only had a basic test kit, but put in 6 jugs of 8% Clorox bleach then more after that to where it has read well above the 5-10 ppm top of the test kit and have kept it there sine Friday (4 days now) But now I can't get the level to go down. I rained about 6" and am getting some fresh water this morning so that will dilute it some. Total chlorine has been reading in the 5-10 ppm on the top of the test kit. The chlorination has been off since yesterday. What should I do now?

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    Re: To drain or not to drain for Nitrates

    A couple correction from my post this morning...pool is actually 28,000 gal. I've put in about 20 jugs of Clorox over the last 4 days (8.25 %, 121 oz). I ordered the test kit from your site today. Just measuring on my kit it is way above the top 10ppm range for FC. The CC looks like it's around the top range of 5-10ppm, leaning more towards the high end. But with the new 6" of water this morning and chlorinator turned off it's not going down at all. Did I add way too much chlorine? What do I do now? CYA according to pool store test was at 109 ppm (shows range should be 30 - 200 so seems normal). PH was 7.1 before adding chlorine. Everything else seemed in normal range. Nitrites at 15 ppm. Help!!

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    Richard320's Avatar
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    Re: Drain for Nitrates?

    Welcome!

    Sad to say, you can't really claim that you "followed the instructions for "slamming" your pool with liquid chlorine." One of the prerequisites is the proper test kit. But you're getting the hang of it - liquid bleach is the way to go.

    Second downer: If the CYA really is 109, the pool water people were right about draining half the water. With 109 CYA, shock level is 43. That would take 17 -yes, 17 - full jugs of 8.25% clorox just to get FC up there. By the time you get the last one emptied, the first one is probably used up! The six gallons you added were a nudge, not a SLAM.

    You won't really know what's going on or how much water to replace until you get accurate test results of your own. Take a few minutes to review the Extended Test Kit Directions, in case any of your readings are off the scale.
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    Re: Drain for Nitrates?

    If the CYA is truly as high as the pool store measures (and you should REALLY test with your own proper test kit to know for sure), then the problem with your pool was not phosphates or nitrates, but a high CYA level since that makes chlorine less effective. You will likely want to do a partial drain/refill to lower the CYA level IF it is indeed that high.

    As for CC in your kit, your kit likely doesn't measure that. If it's a DPD kit measuring shades of pink/red, then it measures FC and TC (total chlorine), NOT CC (combined chlorine). You'd have to calculate CC by subtracting FC from TC.
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    Re: Drain for Nitrates?

    thanks so much! the test kit should come today or tomorrow. can I get an accurate CYA test while the chlorine is still so high? (the kit I have measures in yellow, and I'm above the comparatives on the test into an orange color. It has gone from deep rust to orange so I think it is going down.) When I use the quick strip test it shows my CYA as low to ideal...I think the pool store test may be wrong but we'll soon see.

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    Re: Drain for Nitrates?

    The black dot CYA test shouldn't be affected by the FC level. But the test strip CYA test can be affected by the FC level.
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    Re: Drain for Nitrates?

    and the TFTest kit contains that CYA test, right?

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    Re: Drain for Nitrates?

    Yes.
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    Re: Drain for Nitrates?

    Thanks to this site, I am learning so much about pool chemistry (and what pool chemical stores want to sell)... Thanks for sharing all of your knowledge to help bring me up to speed. It's obvious how important knowing your CYA level is to maintaining the pool. I received the TFTest kit last night. Was tracking the shipping all day and couldn't wait to get home and start testing, so I could start getting some answers. Question about the test: If I am unsure of my reading, can I pour the solution back into the bottle and try again? Does the tube with the black dot need to be rinsed out and dried? How many times can I redo it (maybe asking someone else to try as well just to verify...) Thanks again for all the help!!!

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    Re: Drain for Nitrates?

    Quote Originally Posted by Dlambert301 View Post
    Thanks to this site, I am learning so much about pool chemistry (and what pool chemical stores want to sell)... Thanks for sharing all of your knowledge to help bring me up to speed. It's obvious how important knowing your CYA level is to maintaining the pool. I received the TFTest kit last night. Was tracking the shipping all day and couldn't wait to get home and start testing, so I could start getting some answers. Question about the test: If I am unsure of my reading, can I pour the solution back into the bottle and try again? Does the tube with the black dot need to be rinsed out and dried? How many times can I redo it (maybe asking someone else to try as well just to verify...) Thanks again for all the help!!!
    As many times as you need to. We encourage that. Ten times, twelve times, whatever it takes until you start getting readings that are close to each other. Now remember, if it's above 90, you'll need to use the dilution method in Extended Test Kit Directions.
    16K freeform gunite with spa; Pentair 4000 DE filter; Century Whisperflow 1 HP; Pentair Minimax heater.
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    A pool is like a pet - you have to feed it every day, even the days you don't want to play with it!

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    Re: Drain for Nitrates?

    But the solution for the CYA test is only good for about 5 minutes, so you need to test and pour back and forth fairly quickly.
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    Re: Drain for Nitrates?

    Thanks to all of you, the pool looks beautiful now! The chemistry seems to be adjusted properly and the water is sparkling. I have a question about the chlorine level. With a CYA of 80-90, (have not mastered that test yet) the FCC needs to be up around 7-8 if I recall from the chart. Is it safe to swim at such high levels? Also my heater says not to run it above 5 ppm or you will cause corrosion and void your warranty. I actually swam the other day and the water felt great and I did not have any skin problems. So are levels that high an issue? Thanks again for all the help - this site is fantastic!
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    Re: Drain for Nitrates?

    Quote Originally Posted by Dlambert301 View Post
    Thanks to all of you, the pool looks beautiful now! The chemistry seems to be adjusted properly and the water is sparkling. I have a question about the chlorine level. With a CYA of 80-90, (have not mastered that test yet) the FCC needs to be up around 7-8 if I recall from the chart. Is it safe to swim at such high levels? Also my heater says not to run it above 5 ppm or you will cause corrosion and void your warranty. I actually swam the other day and the water felt great and I did not have any skin problems. So are levels that high an issue? Thanks again for all the help - this site is fantastic!
    Yes, it is safe to swim up to the shock FC level for your CYA level, for you that would be 35. This is the part pool stores don't understand, the CYA/FC relationship. They say 1 - 3 all the time, don't swim above X. But, most of the FC is bound to CYA, not really doing anything. So while you may have a FC of 10, due to your 90 CYA it has the effect of a FC level less than 1 (with no CYA).

    You are a little low with your "recall". With 90 CYA (mine is 80) you want to target 10, with it never going below 7.

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    Re: Drain for Nitrates?

    Thanks so much for the quick reply. It makes perfect sense now!!
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    Re: Drain for Nitrates?

    (belated) Welcome to the forum

    This would have been of more value two weeks ago but in case you're still unsure of your testing TFTestkits has videos : https://www.youtube.com/user/tf100te...e=results_main

    That 5ppm chlorine warning on the heater is common but it's more important to have sanitary water in your pool and for you to be able to keep it from turning green. I'd go with the 10ppm and never below 7 advise (Tim5055) as long as your CYA is at 90. I'd follow the chart - > http://www.troublefreepool.com/conte...art-slam-shock
    I think the equipment manufacturers are more concerned with not seeing someone running really high levels and corroding something drastically while still under warranty and costing them money so it's kind of a cover their but kind of thing. But that's just my guess.

    As for nitrates, 10ppm is what the EPA limits safe drinking water too and I had a relative that needed to bring in bottled water as they couldn't drink from their well due to nitrates (farm fertilizer). At 15ppm it's something you should warn swimmers about and keep pets away from. If that's the level of your wells nitrates are at you likely shouldn't be drinking or cooking with it. At least have it professionally tested to find out.

    I think the only way to get nitrates out of water is with reverse osmosis. It is available for pools in some areas, usually where water is at a premium as it's expensive. Drain and refill would only work to dilute it IF the water you're adding is nitrate free or of a much lower value.
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    Re: Drain for Nitrates?

    The heater manufacturers do not understand the FC/CYA relationship so they are quoting FC values assuming no CYA in the water. Our recommended minimum FC/CYA ratio is equivalent to only 0.06 ppm FC with no CYA so far, far lower than the 5 ppm the heater manufacturers are worried about and also far lower than most commercial/public indoor (and some outdoor) pools that do not use CYA.

    As for nitrates in the pool, I would not worry about it since you are not ingesting large quantities of pool water and it is not volatile and there is no skin absorption (see this link from the EPA).
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    Re: Drain for Nitrates?

    Thanks for the welcome, and the info!
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    Re: Drain for Nitrates?

    Quote Originally Posted by chem geek View Post
    As for nitrates in the pool, I would not worry about it since you are not ingesting large quantities of pool water
    It's not that people ingest much it's that some (hopefully very few) people do drink it. Had a nephew who keep getting sick after swimming and found out he had been drinking the water. You just never know with kids.
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