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Thread: Green pool with high CYA level - SLAM now or replace water to lower CYA first?

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    Green pool with high CYA level - SLAM now or replace water to lower CYA first?

    I'm new to TFP and to pool care in general. I bought a home with a pool in August and learned just enough to keep it up until closing. I'm so happy to have found this forum and the Pool School. I've learned so much over the past couple weeks.

    Here are my current test results:

    FC = 0
    PH = <6.8, my test was light yellow. It's likely lower than that.
    TA = 0
    CH = 110 ppm
    CYA = 100 ppm or greater - my test kit doesn't test higher than this, but I learned today about testing diluted pool water to get a more accurate reading. I will try that tomorrow hopefully and update.
    For some added info, in my area, we get a good amount of rain, so it is common to need to lower the pool level regularly.

    I just took my winter cover off the pool to see that it's green with a nice algae bloom. I wasn't too panicked, because it doesn't look too bad and I know that SLAMing and cleaning it carefully should take care of it. But my high CYA levels means I'm going have to use a TON of chlorine to do it. I believe the former owner used trichlor tablets (cal hypo) exclusively for eight years, and it's clearly taken its toll, though I was glad to see the CH level isn't too bad.

    My questions: Should I go ahead and SLAM the pool now even with the high CYA level or should I replace water to lower the CYA level first? If the former, at what point should I take care of the CYA problem?

    Side questions: My pool does not have a drain at the bottom, so I'll have to drain it from through the skimmer. Given that, would the proper process be to drain it down to the bottom of the skimmer, refill, and repeat until CYA level lowers to normal range? Or do I need to find another way to drain the pool?

    Thank you in advance.


    UPDATE 5/10:

    This morning, I did the CYA test twice with half pool water and half tap water and got some much more encouraging results. Both times I found that my CYA level is only at 80 ppm, not at >100 ppm. Last time was my first time doing the test and I think I fluffed it. I didn't have very good light and I think I stopped pouring too soon. It's the kind of test where you pour a solution of reagent and pool water into a tube until the black dot at the bottom disappears.

    It's still much higher than I would like but at least it's not over 100 ppm like I thought. It will be much easier to fix this with replacing water. Pool Math says replacing 50% of the water will bring it down to 40 ppm and 38% will bring it to 50 ppm.

    It would seem that despite the former owner using trichlor tablets, the CYA level didn't get too out of control. This is likely because we get so much rain in my region that the water is replaced naturally more often than in dryer regions.

    I'm going to try to start draining today if I can.


    UPDATE 5/10, evening:

    The siphon worked like a charm today. Thank you to all for that suggestion and for help on how to do it. I drained a little less than half the pool water and I'm currently refilling it. That probably won't be done until tomorrow afternoon. I'll then let the water circulate a bit before testing and post new test results. I hope this works!

    UPDATE 5/11:

    I finished refilling the water, let it circulate for a few hours and tested. My CYA went down to 40 ppm! I was a little surprised to see my CH didn't change, but it's only at 110 ppm, so that's okay. I'm so relieved this worked. Now I just need to raise my TA, then my PH and then SLAM and clean the pool so I can get swimming! Thank you all for your great advice and support. Test results below:

    CYA - 40 ppm !!
    CH - 110 ppm
    PH - <6.8 - probably much lower
    TA - 0 ppm

    UPDATE 5/15 -

    With advice on another thread, I was able to get my other levels stabilized and my first SLAM has gone surprisingly well. I think I was able to vacuum most of my algae out to waste and the rest was taken care of within the first night and day after adding shock. I passed an OCLT test last night, my CC is at or near 0, and the water is quite clear. Thank you all so much for your advice and encouragement. I'm so glad to have found such kind people on this great forum!

    13113942_814467082022336_1826933389_n.jpg
    Last edited by bjbarlowe; 05-10-2016 at 07:02 PM. Reason: Update
    12250 gallons | IG | Vinyl liner | Sand Filter | Emerson 1081 Pump EUST1102 | Hayward Pro Series High Rate Sand Filter Model #S166T | Pool <10 yrs. old | Taylor K-2006 test kit | SharkVac automatic pool cleaner

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    Texas Splash's Avatar
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    Re: Green pool with high CYA level - SLAM now or replace water to lower CYA first?

    Hello and welcome to TFP! You have the right idea ... water exchange. Draining to the bottom of the skimmer is one way, but not the most efficient. Some people rent a small submersible pump to help with that. But there's no sense adding chemicals to a pool that's going to lose water. At the same time, I would do it as soon as you can. That pH is very corrosive right now. You don't have a heater, but still I wouldn't wait too long. Even if you can only get the CYA down to the 50-ish range (even 60) you have a much more manageable pool for the SLAM. I hope that helps get you started. Keep us posted!
    Pat (a.k.a. Texas Splash) ~ My Pool: Viking Fiberglass; 17,888 Gal; Waterway Supreme 2-sp/2-hp pump; Hayward Ctg filter; TF-100 w/ Speed Stir
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    Re: Green pool with high CYA level - SLAM now or replace water to lower CYA first?

    Home Depot rents submersible pumps.

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    Re: Green pool with high CYA level - SLAM now or replace water to lower CYA first?

    Quote Originally Posted by Texas Splash View Post
    Hello and welcome to TFP! You have the right idea ... water exchange. Draining to the bottom of the skimmer is one way, but not the most efficient. Some people rent a small submersible pump to help with that. But there's no sense adding chemicals to a pool that's going to lose water. At the same time, I would do it as soon as you can. That pH is very corrosive right now. You don't have a heater, but still I wouldn't wait too long. Even if you can only get the CYA down to the 50-ish range (even 60) you have a much more manageable pool for the SLAM. I hope that helps get you started. Keep us posted!
    Thanks so much for the quick reply. I will look into a submersible pump and may try a siphon as well.

    A couple other questions: I have not yet opened the pool or run the filter. I assume to drain the pool, I'll just run the filter in waste mode. Should I unplug the return jets while I'm replacing water or just wait on that until I'm ready to actually add chemicals and filter properly? Lastly, should I refill the pool as I'm draining it and make sure it doesn't get too low? I've read that draining the pool too low can cause damage to in-ground pools.

    Thanks!
    12250 gallons | IG | Vinyl liner | Sand Filter | Emerson 1081 Pump EUST1102 | Hayward Pro Series High Rate Sand Filter Model #S166T | Pool <10 yrs. old | Taylor K-2006 test kit | SharkVac automatic pool cleaner

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    Re: Green pool with high CYA level - SLAM now or replace water to lower CYA first?

    If you try to use the skimmers to drain, once the water is at the bottom of the skimmer opening, the pump can no longer pull water. Then your pump will run dry and burn out. You need to either siphon or rent a submersible seeing as you don't have a bottom drain.

    - - - Updated - - -

    As long as you leave at least a foot of water in the shallow end, you should be okay. If you add water as you drain, you will slow the dilution process.

    - - - Updated - - -

    After you do the dilution test for CYA, you will know how much water you have to drain by using PoolMath.

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    Re: Green pool with high CYA level - SLAM now or replace water to lower CYA first?

    I was looking at this same issue last weekend. CYA at 90 and needing to SLAM due to algae. PoolMath said drain 33% to get to 50 CYA. No bottom drain. I looked into a submersible pump, but someone here suggested siphoning with my vacuum hose. That's what I did. Put the vacuum down to the bottom drain, and filled the hose as if I was going to connect it to the skimmer, but I submerged the end a bit and stuck a lime (a Meyer, I believe) into the end to keep water in. I then dropped it over my pool deck, and the pressure pushed the lime out. Voila...siphoning. I flipped the vacuum upside to make for better inflow. I considered using other hoses for multiple siphons to speed it up, but, I needed them for other tasks.

    Between siphoning and refilling, I was in it for over 2 days (15k gallons out and in). In the end, my CYA came down to 50, and I am now well into my SLAM, seeing good results and the light at the end of the tunnel. No more live algae, just clearing the spent algae.

    I've been here at the TFP Forum for only a few weeks, coming in with a filter and an algae problem. The help and insights here are spot-on, timely, and encouraging. Good luck!!
    55'x20'x10' 50k gallon free-form gunite with waterfall return, Hayward S310S 30" sand filter, Pentair Superflo VS 1.5 hp pump; TF-100 with SpeedStir

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    Re: Green pool with high CYA level - SLAM now or replace water to lower CYA first?

    Sorry, my first post not on my thread, and see now from your signature you have an automatic vacuum. You may not be able to siphon as I did.
    55'x20'x10' 50k gallon free-form gunite with waterfall return, Hayward S310S 30" sand filter, Pentair Superflo VS 1.5 hp pump; TF-100 with SpeedStir

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    Re: Green pool with high CYA level - SLAM now or replace water to lower CYA first?

    No worries, Eric K. I actually have a manual vacuum as well. I use both, because the automatic one doesn't get everything. I love your idea using the lime to plug the hose. I'm definitely going to try siphoning and may look into renting a pump as well. Thanks for the instructions on that, because I was having trouble finding a good guide on siphoning.
    12250 gallons | IG | Vinyl liner | Sand Filter | Emerson 1081 Pump EUST1102 | Hayward Pro Series High Rate Sand Filter Model #S166T | Pool <10 yrs. old | Taylor K-2006 test kit | SharkVac automatic pool cleaner

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    Re: Green pool with high CYA level - SLAM now or replace water to lower CYA first?

    UPDATE:

    This morning, I did the CYA test twice with half pool water and half tap water and got some much more encouraging results. Both times I found that my CYA level is only at 80 ppm, not at >100 ppm. Last time was my first time doing the test and I think I fluffed it. I didn't have very good light and I think I stopped pouring too soon. It's the kind of test where you pour a solution of reagent and pool water into a tube until the black dot at the bottom disappears.

    It's still much higher than I would like but at least it's not over 100 ppm like I thought. It will be much easier to fix this with replacing water. Pool Math says replacing 50% of the water will bring it down to 40 ppm and 38% will bring it to 50 ppm.

    It would seem that despite the former owner using trichlor tablets, the CYA level didn't get too out of control. This is likely because we get so much rain in my region that the water is replaced naturally more often than in dryer regions.

    I'm going to try to start draining today if I can.
    12250 gallons | IG | Vinyl liner | Sand Filter | Emerson 1081 Pump EUST1102 | Hayward Pro Series High Rate Sand Filter Model #S166T | Pool <10 yrs. old | Taylor K-2006 test kit | SharkVac automatic pool cleaner

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    Re: Green pool with high CYA level - SLAM now or replace water to lower CYA first?

    I just want to make sure the 80 is after you doubled since you are testing with half pool water and half tap water. If that number is what you get with half pool water and half tap water, then your CYA is actually 160. I just want to make sure we are all on the same page. Was the number 40 or 80 with half tap and half pool water?
    5900 G Fiberglass IG pool (circa 1990), SWG Hayward Aqua Rite GoldLine (2013), IntelliFlo Variable Speed Pump (2013), Hayward Pro Sand Filter (circa 1990), Well water (no iron or other metals fortunately), test with Taylor K2006C, Charleston, SC

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    Re: Green pool with high CYA level - SLAM now or replace water to lower CYA first?

    Good question. Yes, that's after doubling it. So I tested half pool water and half tap water and got a result of 40. Doubling it gives me 80 ppm. I was surprised to get a different result, but I'm pretty confident with it since I tested it twice. In hindsight, I don't think I did the test quite right the first time. All the advice I got still applies, but it's just less extreme.

    Thanks again. I'll update once I'm able to replace some water and retest.
    12250 gallons | IG | Vinyl liner | Sand Filter | Emerson 1081 Pump EUST1102 | Hayward Pro Series High Rate Sand Filter Model #S166T | Pool <10 yrs. old | Taylor K-2006 test kit | SharkVac automatic pool cleaner

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    Re: Green pool with high CYA level - SLAM now or replace water to lower CYA first?

    OK. Just to be sure, since you are below 100, you could test with full pool water just to confirm.
    5900 G Fiberglass IG pool (circa 1990), SWG Hayward Aqua Rite GoldLine (2013), IntelliFlo Variable Speed Pump (2013), Hayward Pro Sand Filter (circa 1990), Well water (no iron or other metals fortunately), test with Taylor K2006C, Charleston, SC

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    Re: Green pool with high CYA level - SLAM now or replace water to lower CYA first?

    Ah, that's a good suggestion. However, before I saw that, I already started the process of replacing water. I've drained a little less than half of the pool and I'm currently refilling it. I'll finish refilling it and let the water circulate a bit before trying the test again.
    12250 gallons | IG | Vinyl liner | Sand Filter | Emerson 1081 Pump EUST1102 | Hayward Pro Series High Rate Sand Filter Model #S166T | Pool <10 yrs. old | Taylor K-2006 test kit | SharkVac automatic pool cleaner

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