Florida Pool - High CYA - Partial Drain - Afaid of Pool Popping Out of Ground

Peterc424

New member
Aug 4, 2015
3
Winter Park, Florida
I recently bought a house with a pool and started to do the pool maintenance after the previous owner's pool guy retired. He gave me some tips to clean, balance, and chlorinate the pool... but now I am running into some issues. He recommended I use 1 or 2 "In the Swim" 3 inch Chlorine tablets (99% Trichloro-S-Triazinetrione) each week and "In the Swim" Pool Shock (68% Calcium Hypochlorite) each week or as needed. I bought the TF-100 test kit a month or so ago and noticed I had very high CYA values. I just tested the pool today and here are my values:

FC: 5.5
CC: 1.0
TC: 6.5
CH: 475
TA: 100
CYA: 100++
PH: 7.6

I know my CYA is super high, when I use the TF-100 CYA test I can't see the black dot well before the water even approach the 100 tick mark. After reading the forums here I realize I should be moving over to liquid chlorine and save the tablets for when I am away... which I plan to do. I also saw I need to do a partial drain to lower my CYA... but after reading a bunch of stuff online I am afraid of popping the pool if I do a partial drain.

Is this something I need to worry about even if I only do a partial drain? I live in the Orlando Florida area... and honestly have no clue what my water table levels are in the area. I also have no clue if I have a hydrostatic valve or not. Should I be hiring a professional company... or is this something I can do myself? I know I can drain water out through my Hayward filter.... but don't want to attempt it if I could cause serious damage to my pool. Any advice would be highly appreciated!

Thanks so much,
Peter
 

dmorriso

Member
Sep 11, 2015
22
Orlando, FL
Is this something I need to worry about even if I only do a partial drain? I live in the Orlando Florida area... and honestly have no clue what my water table levels are in the area. I also have no clue if I have a hydrostatic valve or not. Should I be hiring a professional company... or is this something I can do myself? I know I can drain water out through my Hayward filter.... but don't want to attempt it if I could cause serious damage to my pool.
I'm in the Orlando area too, and need to do a partial drain/fill to lower CYA and CH. I don't want to risk draining, the water table isn't very deep.

I bought a submersible pump at Harbor Freight for $36. I plan to put that on the top step of the shallow end, and attach a hose to a weight at the corner of the deep end. With the cold water sitting at the bottom, I'm hoping that I can get a decent exchange before the water mixes too much. I plan to test the outflow every 30 minutes or so until I see the FC dropping a lot.

Unfortunately, I'm not going to do this until Halloweenish, and you probably need to fix your CYA levels sooner than that... So by the time I know how this will work, it might be too late for your use.


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Divin Dave

TFP Expert
LifeTime Supporter
Oct 2, 2013
5,681
Longview, Texas
Certainly being in FL, hydrostatic pressure must be contended with.

The method dimorisso describes above however is safe. Add water to the bottom of the deep end, and pump out water from the shallow end.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
14,843
Evans, Georgia
I think you're smart to be cautious of a high water table there in FL.

But you can do multiple smaller drains-->refills--> drain again--> refill.... drain a third of the pool and after the refill test your CYA again. In the end while this does end up using more water the pool isn't drained so much at one time that it is at risk.

After you get your CYA to a manageable level you can address that CC of 1 and see if you need to perform a SLAM procedure.
 

Peterc424

New member
Aug 4, 2015
3
Winter Park, Florida
Thanks all for responding so far... owning a pool is much less intimidating when you have such a great resource like this site to back you up!

So the two suggested options to mitigate the risk of popping the pool is to

(1) use a pump in shallow end and refill in the deep end at the same time
(2) do small drains and refills multiple times

For #1... dmorriso, what pump did you get from Harbor Freight Tools? How many gallons per hour? I assume you would want something to match the input of the garden hose so you are not draining faster than refilling.

For #2... I was kinda of leaning towards this options originally just because I did not have a pump. I was planning to use my pool equipment to either drain water from my skimmer or main drain. Which one would be the better option for partial drains? I assume if I choose the skimmer I would just have to make sure I turn off the pump before it gets below the skimmer... which would require a lot of babysitting. Maybe the main drain would be better? Also... I guess my concern here was how much can I drain without risking the pool from popping out? The depth of the pool is about 6ft in the deep end. I would rather be conservative and take less out and have to drain/refill more times than having the pool popping out.
 

DaninFLA

Well-known member
Apr 29, 2015
1,011
Sarasota, FL
have you checked your water table? its going to be more efficient to drain and then refill as opposed to continuous drain and refill. checking your actual water table depth (which can vary by as much as a couple of feet during the year) is very simple. just dig a hole as close to your pool deck as you can get, dig it down to the level you want to drain, i.e. if you want to remove 2 feet of water, dig the hole down 2 feet. if you dig the hole, let it sit for a few hours and there is no water in the hole, then your water table is lower. you can safely lower your pool level 1/2-1 foot below the water table without it popping, but keeping it at least even with the water table is safest. if you are able to drain 50% of your pool, do that. its going to use less water and take less time than multiple smaller refills. remember two 25% refills is not the same as one 50% refill

that would be my recommendation.

as far as draining goes, close your valve so you are not pulling from the skimmer, if it goes dry your pump is going to burn up.
 

dmorriso

Member
Sep 11, 2015
22
Orlando, FL
FWIW, I can get water in a hole 2ft under my pool water surface. In my opinion, it isn't worth the risk (but I only need a 50% change).

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DaninFLA

Well-known member
Apr 29, 2015
1,011
Sarasota, FL
FYI, I can get water in a hole 2ft under my pool water surface. In my opinion, it isn't worth the risk (but I only need a 50% change).

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well 2 feet for a lot of people would represent about 50% of their pool volume, so that's pretty good. wont know until you dig. there is literally zero risk of popping the pool until the water level in your pool is lower than groundwater. so if its 2 feet deep, 2 feet lowering of your pool will not result in ANY hydrostatic pressure. going 6" would be very minimal with real risk.