Become a TFP Supporter Pool Math Forum Rules Pool School
Results 1 to 8 of 8

Thread: Large CYA drop over winter?

  1. Back To Top    #1

    Join Date
    Aug 2016
    Location
    Byron, Il
    Posts
    28

    Large CYA drop over winter?

    Last fall I tested CYA and it came in at over near or over 100. Just tested to start getting ready to open and I have a CYA of...well near zero. I filled the tube to the top and could still easily see the dot. We've had a significant amount of rain as the pool is near the top at this point and needs some drained out. I'm just wondering if such a significant drop normal over winter or is it possible my reagent is bad, less then a year old purchased last Aug or so.

    Thanks

    Matt
    15K gal, IG vinyl, Sand Hayward, Hayward Pump single speed, Install 2004, TF-100, city water.

  2. Back To Top    #2
    Self Evident's Avatar
    Join Date
    Jul 2016
    Location
    Polk County, FL
    Posts
    29

    Re: Large CYA drop over winter?

    You will experience some CYA loss over the winter. how much depends on ... ummm.. I don't know. But, for example, over this past winter, from early October thru late March, my CYA dropped from 40 to much less than 20 (not zero, but no where near 20).

    Now, I opened to a clear & clean pool. Was your pool likewise, or was it a bit on the green side? As an other example- last year, I opened to a swamp and had a true zero CYA. Now, I don't know what it was at the end of the prior season, but, at that point, this pool had been chlorinated almost exclusively by pucks, so it's CYA was probably very high. Until I stopped caring for it at all from Sep '15 thru Jul '16.

    Another consideration is that when you took your water sample, had you ran the pump to mix the water first? If not, you may have tested a mostly rain water sample. Just a thought...
    IG 30'x15' oval. ~12,800 gal. Vinyl lined. 24" Hayward sand filter w/ 1.5 HP pump. TF-100 test kit. All hail the Speed Stir!

  3. Back To Top    #3

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,941

    Re: Large CYA drop over winter?

    I doubt the reagent is bad, We have reasonably common reports of CYA loss over the winter......yours is pretty drastic.

    It actually brings up another issue.....ammonia.

    Get your pump and everything up and running. Put in enough liquid chlorine to get to say, 10 ppm. Now check it in about 15 minutes. If the FC is gone or almost gone, your CYA converted to ammonia.

    Let us know if that happens and we'll tell you how to get it out (easy).
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  4. Back To Top    #4
    JayG's Avatar
    Join Date
    Aug 2015
    Location
    Harrison, NY
    Posts
    206

    Re: Large CYA drop over winter?

    In the northeast although we had a lot of precipitation over the winter my CYA went from 65 to ~10....more of a drop than I expected. I added dichlor to both add FC and add CYA. My CYA is now 50 and FC has been relatively stable since that addition, so I don't think ammonia is/was our problem. This is only my second season in our pool, so I'm new to this. I thought I'd just add a data point.
    Jay--Metro NYC
    35K gal, in-ground, free-form, pebble finish, 2 skimmers, 3 returns, autofill. No spa, no features. Partial shade.
    Pentair C&C cartridge filter (400 sq in), Pentair VS pump, Pentair 140 btu heat pump, Triton Plus Robo-cleaner; Stenner with 55 gal bleach cistern. TFT 100 test kit.

  5. Back To Top    #5

    Join Date
    Aug 2016
    Location
    Byron, Il
    Posts
    28

    Re: Large CYA drop over winter?

    Quote Originally Posted by Self Evident View Post
    Now, I opened to a clear & clean pool. Was your pool likewise, or was it a bit on the green side?

    Another consideration is that when you took your water sample, had you ran the pump to mix the water first? If not, you may have tested a mostly rain water sample. Just a thought...
    This is an interesting point that may be exactly the case. We got a lot of rain plus the snow over winter so there's no way to get down to where "Last years" water might be. Also I do have some green but there is a pretty clear dividing line as to where it starts and stops...and it's all toward the top. I could have layers of water, old pool water down below and rain water above.

    I have a new multi port coming in today and will get that installed, pump running etc and test again to see if once mixed I get higher numbers.

    Thanks.

    - - - Updated - - -

    Quote Originally Posted by duraleigh View Post
    I doubt the reagent is bad, We have reasonably common reports of CYA loss over the winter......yours is pretty drastic.

    It actually brings up another issue.....ammonia.

    Get your pump and everything up and running. Put in enough liquid chlorine to get to say, 10 ppm. Now check it in about 15 minutes. If the FC is gone or almost gone, your CYA converted to ammonia.

    Let us know if that happens and we'll tell you how to get it out (easy).
    I will do both of the above once I have the pump running. I will clear out some of the larger gunk, get the pump running and let it run for a while to mix things up and then test. If the CYA jumps up I know I had layered water. If it doesn't I will do your test.

    Thanks,

    Matt
    15K gal, IG vinyl, Sand Hayward, Hayward Pump single speed, Install 2004, TF-100, city water.

  6. Back To Top    #6

    In the Industry

    duraleigh's Avatar
    Join Date
    Apr 2007
    Location
    Sebring, Florida
    Posts
    30,941

    Re: Large CYA drop over winter?

    I will do both of the above once I have the pump running. I will clear out some of the larger gunk, get the pump running and let it run for a while to mix things up and then test. If the CYA jumps up I know I had layered water. If it doesn't I will do your test.
    Good plan!
    Dave S.
    42k vinyl and concrete pool, 1.5hp pump, 140gpm filter
    TFTestkits , PoolMath , Pool School

  7. Back To Top    #7

    Join Date
    Mar 2016
    Location
    Shakopee
    Posts
    19

    Re: Large CYA drop over winter?

    Just a CYA question in general.
    Is it expected that CYA would vary much during the season.

    To me it seems like once you get it to a certain level it would stay pretty established during the year if there is outside water being added to the pool.

    Is this an accurate assumption or am I wrong?
    18x40 - 22,600 Gallon, In Ground Vinyl built 2016. IC-40 SWG, Pentair VS pump, autocover.

  8. Back To Top    #8
    Mod Squad pooldv's Avatar
    Join Date
    Aug 2012
    Location
    DFW, TX
    Posts
    24,974

    Re: Large CYA drop over winter?

    Cya drops 3-5 ppm per month on average.
    TFP Moderator
    If TFP helped you or saved you money - Become a TFP Supporter! <--Click here
    2012 build and pics, 20k gal gunite, black onyx pebblesheen, OK flagstone, IntellifoVS, cart filter w/Pleatco, IC40 SWG, Solartouch, 5 12'x4' solar panels, HP50HA heat pump, 8mil solar cover, borates, TF-100 test kit, SONOS, Doheny's Discovery Robot, hot tub on bleach

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •