No Total Or Free Chlorine And Pool Can't Hold Cyanuric Acid (CYA)
by Gary
I'm unable to keep any amount of chlorine in my pool, total or free. Even after shocking in the evening to 20ppm after the sun was no longer on the pool, the level dropped back to zero within a couple hours. The water has been tested by two different pool testing places and everything is in range except for chlorine. Also, CYA dropped from 31ppm to 8ppm in one day? (The first test done by our local ACE Hardware store read 31 and the second the next day by a pool store read 8. My test strips actually concurred with both tests.) This problem actually started last summer with an intense heat buildup and I have yet to get it under control even after shocking many times. Pool temp is 82F. The liner was replaced in 2004 and the pool water has not been changed since except of course rain and to add water due to evaporation. Should I drain the pool and start over? Not concerned about structure with draining. It's been done before and designed to stand empty. Thanks for the question Gary My first question would be are you testing with strips or a Taylor FAS-DPD K-2006 test kit. It's this kit that you should be using. Pool Water Testing Water Testing Kit Here's another post you may want to read: No Free Or Total Chlorine In The Pool! Next, you should shock at night and take another reading in the morning after the filter been able to run for the entire night. Does the shock hold until morning? If it does hold but the chlorine is dissipating through the day, you probably don't have enough CYA/stabilizer in the pool water. It should be between 30 - 50ppm. It may take a few days to a week for CYA to show up in the pool if it's being added every or every other day. Use Dichlor shock and Trichlor tabs to keep the CYA in check. If you chlorine reading is showing nothing, there may be a chance that the chlorine is so high that it's actually bleaching out. This happened to one of the guards at the YMCA. There was an accident in the hot tub, (puke I think), so she put alot of chlorine in to take care of the problem. She tested the chlorine after 30 minutes and there was no reading. She called me and I went down to the Y and tested it myself. Sure enough, it registered zero. So here's what I did and what you can do. Take the vial (with the FAS-DPD kit) and fill it up to the 25ml mark with pool water, then fill the rest of the way, up to the 44ml mark, with tap water. What you just did is dilute the chlorine level. Mix it up a little. Then pour out to the 25ml mark. Run your test as usual. When you get a reading, simply double it and you'll have your chlorine reading. This will tell you if you have bleached out the first reading. If you don't have an FAS-DPD kit, you can dilute a sample and take that into your local pool store for analysis. It might be that your chlorine demand was caused by something that got into your water. Ammonia from bacteria may cause a higher than normal chlorine demand. CYA can be used up by anerobic bacteria in a closed pool. The bacteria will excrete ammonia compounds in the pool. If the bacteria is the problem, you'll need to basically shock and keep the chlorine level to about 15ppm all day long until the chlorine holds. It may take lots of chlorine to do this and the expense will probably add up pretty quickly. If you keep shocking and have the CYA in line, and all of the other chemical readings are in line, as a last resort, I would advise you to drain at minimum 1/2 of the water and restart. The bacteria producing ammonia would be my best guess. By the way, the guard who put the chlorine in the hot tub got the chlorine reading up to 80ppm. Hope this helps and good luck with your pool. Robert Follow Up Comment: No Free Or Total Chlorine In The Pool By: Gary Date: June 3, 2011 Robert, thanks for your comments -- much appreciated! I do shock my pool at night and have raised it to about 20ppm chlorine the last two nights only to have a 0 reading within a few hours. I have no chlorine remaining, total or fee, by morning. Also, I do have a Taylor FAS-DPD Pool Water Test Kit K-2006 on order but I've been using test strips or reagents at home with an occasional test at our local pool store until it closed 3-4 years ago. Your comments about anerobic bacteria are quite helpful. I'm starting to think that this problem has been building for several years and just hit the flash point last summer when the pool hit a new high temperature. And ammonia produced by the bacteria may also explain why I've had trouble keeping CYA within range. None of my previous home testing provided "Total and Free" Chlorine, just "Chlorine." And since the water in my pool has been crystal clear and easy to balance, and the Aqua Rite generator has consistently maintained chlorine I didn't think it necessary to shock the pool on a regular basis or drive to another town to have the water tested. But thinking back, I have had a growing algae problem which may have been an indicator that CC was climbing and FC declining. I now also remember having a similar chlorine problem about 7-8 years ago which I blamed erroneously on the chlorine generator. At about the same time we lost our liner to a hurricane and once it was replaced and the pool filled with fresh water the chlorine problem went away. So this is a long winded way of saying, I'm draining the pool and I will pay much more attention to CC and FC in the future. Thanks again! You were very helpful. Gary Follow Up Comment By: Robert Date: June 3, 2011 Long winded is always good. It gives people the answers they need. Thanks and have fun with your pool. Robert Comment: "No Chlorine" Problem Solved By: Gary Date: Jun 30, 2011 I finally solved the "no chlorine" problem. I drained a little over half of the water and refilled. Then brought the CYA to target, balanced and added salt for the SWG but didn't turn it on. Testing showed zero chlorine. I then shocked heavy 2x per day early morning and after sunset raising chlorine to around 20ppm each time. Day 1 chlorine totally disappears in 2 hrs. Day 2 held for about 4 hours. Morning of day 3 held about 6, and evening held all night and next day. I left the SWG off but it still took 3 days to fall back to 4ppm. The water is balanced and never looked better, and is holding Chlorine so well I have to the SWG off for a day or more at a time to stay below 3ppm. Even with it set at 20%. Thanks for the help! Gary Comment By: Robert Date: June 30, 2011 Congratulations on your perfectly balanced pool. And the Summer is still young so go enjoy it. That's what it's all about. New Question: CYA wont get above 35 By: Kirsten Date: Jun 30, 2011 Hi. I'm a new pool owner and doing pretty good I guess. My only question is why I can't seem to get my CYA above 35. Pool is 15 x 30 4' deep oval above ground, vinyl, sits in the sun 10 hours a day. My FC is 4 but the CYA is still low. I'm constantly putting bleach in the pool. I've added stabilizer twice now, waited a full week and it barely raised it. Any ideas? Oh, and I'm using the Taylor FAS-DPD test kit, so it should be accurate. Answer By: Robert Date: June 30, 2011 Thanks for the question Kirsten and glad you found my site. If you have any other questions I'd encourage you to use the "Ask The Expert" or "Contact Me" button on the Navbar to the left, or go to one of the many pages I have invitations on. You can ask your question there and hit submit. It will take you another page to ask if you want to know when a reply is made. Simply put your email address in the box and hit send. Your email is safe and no one who visits the site will see it. Doing this will create a page specifically for your question and you can refer back to it whenever you want. I also make follow up comments on the page so there's no need to flip back and forth from one page to the next. Your CYA is the stabilizer for the pool, as you know. For home pools it should be between 30 - 50ppm. The easiest way to increase your CYA is to use Dichlor. This is a stabilized form of chlorine. Be careful when using this because your CYA can get out of hand quickly. For every 10ppm of chlorine added with Dichlor, you'll raise the CYA 9ppm. You can also use Trichlor tabs for weekly chlorine maintenance, with manually dosing your pool with either bleach or chlorine. Trichlor will slowly increase the CYA as well. For every 10ppm of added chlorine with Trichlor, your CYA will be raised 6ppm. Bleach is unstabilized and will not raise the CYA, but is the same as regular pool chlorine. It's just about 1/2 the strength. If I were you I'd keep the CYA where it is. There's really no need to raise it. Once it is raised, the chlorine must be raised as well in proportion to the CYA. The CYA should be 7.5% of your chlorine. If you're running the chlorine at 2.5ppm, simply multiply that by 7.5% and you get 33. Your chlorine is 4ppm which is fine. If the CYA get too high the only way to reduce it is a partial drain and refill. Hope this helps and have a fun and safe Summer. Let me know when you get this reply. Robert |
