help figuring out how much water

[ajackson]

I have a Foxx Lagoon style pool 29.5 x 19 at it widest point. 3 feet to 6.5
It is 19.5 ft at widest point
15 ft across the deep end
Slope starts 18 ft from the deep end wall
Pool hold 14,500 gallons

I need to dump alot of water.. like 1/2 or more because of CYA level. I found someone that could bring me 7200 gallons but I have NO idea how far down I should drain and I dont want to mess up the liner by taking out to much.
Can you help? my drawing is REALLY rough...but I hope it helps figure this out

 

[jblizzle]

Well, before I saw your 14500 number, I actually calculated the same thing.

I would say draining about 2 feet would be about half your water.
With a liner, you should leave at least 1 foot of water in the shallow end. Also there is some risk to the liner floating if you drain below the ground water level ... any idea what that level is? If you can dig a 2 foot hole without water appearing in it, you should be fine.

 

[ajackson]

You are fast... Thank you ...
About the ground water. It has not hardly rained her at all this summer. When they dug the hole for the pool it didnt get water in it until the day after.. then only a about 1ft.
when we put our fence up around the pool we trenched them about 2.5 to 3 feet and they didnt have water in them at all.

The guy isnt coming until Friday afternoon.. Do you think it is safe to drain it out on Thursday evening ?? Or should I see if I can have someone come over and drain on Friday morning?

 

[jblizzle]

Based on what you wrote, it sounds like the ground water "should" not be a problem.

Honestly, I do not know the risks of leaving a liner pool half full for a day ... probably OK, but I can not guarantee it. The risk is yours to decide.

Hopefully someone else can offer a thought on this.

 

[ajackson]

Ok.. I will wait and see
Thanks again

 

[Bama Rambler]

If the liner is only a few years old you should be fine to drain it tonight and refill it tomorrow. If you think about it, the part of the liner above the waterline is always out of the water.

I get between 2 and 3 feet deep as half your water. As JB said, leave about 6" to a foot of water in the shallow end to prevent the liner from slipping and wrinkling.

 

[ajackson]

ok. It is done.. Wow that took longer than I thought it would.. 3 hours later I now have 24 inches less water. I left 13 in the shallow end... I sure hope this works.
water guy is coming in the morning to put 7200 gallons back in it
Do when I get home tomorrow after work I will test water and post my results on the site.
I assume this should drop my cya back into the 80-100 range ??

 

[jblizzle]

I never saw your posted CYA before the water change ... you should get close to a 50% reduction.

 

[Bama Rambler]

Are you set up to pump to waste when the water guy gets there? It would be a good idea just in case he has more water than you've pumped out. That way you could turn the pump on and pump out a little more and it'll help your CYA a little more too.

Let us know how it goes.

 

[ajackson]

Ok.. he came today... Thanks for everyones Help.. My CYA was at leat 160. now I am reading between 80-90 That sucker is hard to read... did the test twice with 1/2 pool 1/2 well and then x2
It is a good thing I dumped it last night because even though I did it to waste it still took 3 hours... This was alot due to me having to duct tape the 2 hoses together because pressure kept wearing thru the tape. Normally our back wash is just plumbed into our downspout. But I really didnt want 7600 gallons going into that pipe (might have flooded the basment or leach bed)
So I just ran a 30 ft house out into the back yard from the filter.
I am Happy for your advice.. Even thou it is still cloudy my CYA will be alot more managable.
thanks again