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Thread: CYA > 100, issue with FC in pool

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    CYA > 100, issue with FC in pool

    I recently noticed I was having to add an unusual amount of chlorine in order to get much of a FC reading on my kit (prior to this we had record rainfall, 10" or more over a 5 day period). During this rainstorm, I backwashed probably 1200 gallons or so out of the pool. I have a couple stains that were in the pool prior to me purchasing the home that only show when PH is low. Seeing these, I checked the balance. PH was low. FC was almost non-existent. CC was higher than FC. CYA seemed normal. So I shocked it with trichlor shock. I added chlorine to my pool as normal and continued. As the FC dropped from the shock, I noticed it kept falling even though I had 2 3" pucks in the chlorinator (15,000 gal pool - small). I am only running my pump about 4.5 hours over the winter time in Alabama (because it worked fine last year - no algae). I took a sample to my pool store today and the CYA was around 144, FC at .75, CC at 1.0. They recommended I put a pound of Calcium Hypochlorite (73%) to shock and get rid of the CC. I thought I did that last week with the trichlor (2 lbs). I suppose the CYA has gotten too high and now is requiring a lot of chlorine? Can you tell me if you think using the GLB CalHypo is going to make a difference? Or should I just drop a hose in there and backwash half the pool out? Thanks.

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    Mod Squad jblizzle's Avatar
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    Re: CYA > 100, issue with FC in pool

    Welcome to TFP!!!

    Nope, the Cal Hypo will not help in the long run. Your problem is a lack of understanding (by you and the pool store) about the relationship between CYA and FC. The higher the CYA, the higher the FC must be maintained to prevent algae from starting. If your FC is dropping fast with a high CYA, that menas you have something in the water consuming it quickly.

    My recommendations:
    1. Order one of the test kits we recommend and stop relying on the pool store that is giving you bad information
    2. Read Pool School (button at upper right of page) a few times to understand the chemistry and allow you to take control.
    3. Replace a lot of water to get the CYA in the recommended range ... note that there is a risk of lowering the water level too much and the pool floating out of the ground depending on your ground water level
    4. Go through the Shock Process (see Pool School)
    5. Stop using forms of chlorine that are adding the CYA to your pool (tablets and trichlor shock)

    Also add your pool information as described here: pool-school/read_before_you_post
    Jason, TFP Moderator
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    Re: CYA > 100, issue with FC in pool

    Quote Originally Posted by jblizzle
    Welcome to TFP!!!

    Nope, the Cal Hypo will not help in the long run. Your problem is a lack of understanding (by you and the pool store) about the relationship between CYA and FC. The higher the CYA, the higher the FC must be maintained to prevent algae from starting. If your FC is dropping fast with a high CYA, that menas you have something in the water consuming it quickly.

    My recommendations:
    1. Order one of the test kits we recommend and stop relying on the pool store that is giving you bad information
    2. Read Pool School (button at upper right of page) a few times to understand the chemistry and allow you to take control.
    3. Replace a lot of water to get the CYA in the recommended range ... note that there is a risk of lowering the water level too much and the pool floating out of the ground depending on your ground water level
    4. Go through the Shock Process (see Pool School)
    5. Stop using forms of chlorine that are adding the CYA to your pool (tablets and trichlor shock)

    Also add your pool information as described here: pool-school/read_before_you_post
    I have a Taylor Test kit and also test strips (just to compare 2 readings and keep both honest). I have been taking care of a pool for a while and have read many, many posts here and all over the internet. I have a pretty good understanding about how the chemistry works together. Is draining the water the only way to rid excess CYA? And if so, what is the best way to drain some water without using a $100 sump pump? Can I just pop a hose in there and backwash down to when the pump gets close to dry and then fill with hose, and continue that until the CYA is lower? And you are suggesting to stop using trichlor tablets .. what do I use in place of that? I have an aqua genie chlorinator (an all-in-one skimmer/return with a plastic box that fills with water and flows into the skimmer to add FC to the pool). The reason I think the pool store recommended shocking with calcium is b.c. the CYA is high and it will rid me of the CC which will in turn allow FC to populate right? Thank you. Taking a glance over pool school again now

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    Mod Squad jblizzle's Avatar
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    Re: CYA > 100, issue with FC in pool

    Which Taylor Test Kit? The FAS-DPD chlorine test is the key to a good test kit. It must also test for pH, TA, CH and CYA. The test strips are worthless.

    Only 2 ways to removed CYA from the water, pump it out OR reverse osmosis (which is available only in limited areas and costs a few $100 bucks).

    If you can isolate a floor drain, you can use the pool pump to lower the water level (still no idea if this is AG or IG pool). If AG, you could just use a hose as siphon. If IG, you will need a pump ... renting a submersible pump from Home Depot is less than $50/day. Or Harbor Freight sells cheap ones as well.

    Tablets add CYA ... so does Dichlor. Cal-hypo ads calcium. Both are bad if they get too high. Best source of chlorine is liquid (bleach) as it does not affect CH or CYA or pH.

    CC are just a sign that the FC is being consumed. You will not know if you kill everything in the pool consuming the FC unless you follow the Shock Process until you pass the 3 tests to stop. To do this correctly, you need the FAS-DPD test.

    The FC/CYA chart in Pool School should be eye-opening. You CYA is off the chart AND realize that CYA is notoriously the test that pool stores are the worst at ... so who knows what your actual CYA level is. Assuming your CYA is 150ppm, to shock the pool correctly you have to maintain a FC level of 40+ppm. And you should NEVER let the FC below ~11ppm or algae can start to grow. And BTW, the pH test become in accurate when the FC is > 10ppm.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
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    Re: CYA > 100, issue with FC in pool

    Quote Originally Posted by jblizzle
    Which Taylor Test Kit? The FAS-DPD chlorine test is the key to a good test kit. It must also test for pH, TA, CH and CYA. The test strips are worthless.

    Only 2 ways to removed CYA from the water, pump it out OR reverse osmosis (which is available only in limited areas and costs a few $100 bucks).

    If you can isolate a floor drain, you can use the pool pump to lower the water level (still no idea if this is AG or IG pool). If AG, you could just use a hose as siphon. If IG, you will need a pump ... renting a submersible pump from Home Depot is less than $50/day. Or Harbor Freight sells cheap ones as well.

    Tablets add CYA ... so does Dichlor. Cal-hypo ads calcium. Both are bad if they get too high. Best source of chlorine is liquid (bleach) as it does not affect CH or CYA or pH.

    CC are just a sign that the FC is being consumed. You will not know if you kill everything in the pool consuming the FC unless you follow the Shock Process until you pass the 3 tests to stop. To do this correctly, you need the FAS-DPD test.

    The FC/CYA chart in Pool School should be eye-opening. You CYA is off the chart AND realize that CYA is notoriously the test that pool stores are the worst at ... so who knows what your actual CYA level is. Assuming your CYA is 150ppm, to shock the pool correctly you have to maintain a FC level of 40+ppm. And you should NEVER let the FC below ~11ppm or algae can start to grow. And BTW, the pH test become in accurate when the FC is > 10ppm.
    Sorry about that. It is an IG pool. Unfortunately, my pool does not have a main drain, but can I hook my vacuum hose to the skimmer and pump it out through the pump that way? I realize at some point I might lose suction when the water level drops below the skimmer, but at that point adding water. Would that be sufficient? I was just reading that CYA is notoriously off at the pool stores. I have a modified Taylor i1005 (I am using the K-2006 PH chemicals and testing block. I do not have the FAS-DPD part, just drops) I am going to test the CYA when I get home. However, what is the typical amount of time you can go without having to drain and re-add water (concerning stabilizer) by using Trichlor? I do not shock until I notice a chlorine smell or CC is above FC (in which you begin to see FC levels getting lower with the same amount of chlorine added before). I do my best to keep the pool as balanced as possible so my checkbook stays the same Thanks for the responses and help

    P.S. If I were to use bleach, how often would I have to apply this to the pool to maintain the levels needed (ppm 1-3)?

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    Mod Squad Bama Rambler's Avatar
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    Re: CYA > 100, issue with FC in pool

    There are a few things you need to do. Start by reading Pool School and learning the method we use here. You'll find out that using pucks isn't the best for your pool or your wallet.

    Second is to get a good test kit so you'll know where you're at and what needs adjusting.

    You'll need to add bleach every day or at the very least every other day. There are automated ways of getting FC into the pool, but using bleach is where you should start. It allows you to learn your pool.

    Once you learn the mothod here you'll likely never have to so called "shock" the pool again.

    There's no way to say how long you can go before the CYA gets out of hand using pucks, as each pool and situation is different.
    Dave J. TFP Moderator
    24' x 52" Round AGP. 2hp/¼hp SPL Power-Flo 2-speed pump. 200sqft Waterway Cartridge Filter. 45MHP2(3GPD) Stenner Peristaltic Pump
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    Mod Squad jblizzle's Avatar
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    Re: CYA > 100, issue with FC in pool

    To address your P.S ... The amount of FC required, depends on what your CYA level is. We would NEVER recommend letting it drop down below 2ppm and if you are at the higher recommend CYA level of 50ppm; then the FC should NEVER be less than 4ppm:

    pool-school/chlorine_cya_chart_shock
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
    If you found TFP helpful and we saved you money ... Become a TFP Supporter!

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    Re: CYA > 100, issue with FC in pool

    Quote Originally Posted by Bama Rambler
    There are a few things you need to do. Start by reading Pool School and learning the method we use here. You'll find out that using pucks isn't the best for your pool or your wallet.

    Second is to get a good test kit so you'll know where you're at and what needs adjusting.

    You'll need to add bleach every day or at the very least every other day. There are automated ways of getting FC into the pool, but using bleach is where you should start. It allows you to learn your pool.

    Once you learn the mothod here you'll likely never have to so called "shock" the pool again.

    There's no way to say how long you can go before the CYA gets out of hand using pucks, as each pool and situation is different.
    Dave,
    Adding chlorine daily brings something to my attention as well. I am usually ok with that. However, in May I will be out of the country for 2 week and will not be able to add it daily at that point. What would you suggest doing in that scenario? And also, no one ever answered my question about if I drain water to the bottom of the skimmer using the pool pump, then adding water and repeating would help to reduce CYA without having to rent/buy pump. Thanks in advance. - Josh

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    Re: CYA > 100, issue with FC in pool

    And also, no one ever answered my question about if I drain water to the bottom of the skimmer using the pool pump, then adding water and repeating would help to reduce CYA without having to rent/buy pump
    Can you simply backwash it out? Repeatedly if necessary.

    Get your CYA down lower than normal before you leave then you can use pucks for the time you are gone.
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
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    Mod Squad Bama Rambler's Avatar
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    Re: CYA > 100, issue with FC in pool

    Since you don't have a main drain you can hook up the vacuum hose and pump the water down a long way. You most likely won't lose prime until you shut the pump off. I'd pump about half of the water out and then refill and see where the CYA is at and do it again if needed.

    If you're going to be gone for 2 weeks I'd suggest you either get an injection pump or a swcg. You'll still need someone to stop every few days and check on things to make sure everything is running ok but they won't have to add anything.
    Dave J. TFP Moderator
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