Self Install - 24' x 54" questions on Sand Base / Cove

[mleega]

Pool install in progress. Still in process of leveling ground, but hope to be ready for the actual install this weekend....
I have watched several videos, read the instructions, etc - and still have some basic questions.
I purchased Foam Cove forms for the pool, and would like to know the best way to fit them properly (not completely opposed to eating the money for them if a clay/dirt cove is better for longevity - but i have them

From what i have read, and i understand the reasoning - you do NOT want a cove made of sand due to inherent instability and can not compact/form it like you can georgia red clay or dirt
With that said - i am a little confused - if there is a 2 inch sand base - and foam cove on top of that, is that not almost the same as a 'sand cove' Like this image :


It seems that the sand would wash out from under it.....
So this may be a better alternative :


But that option really reduces the effective size / height of the foam cove

So i thought of a 3rd alternative :

Which seems to address both concerns (at least in my mind)

My first question is - WHAT IS THE RIGHT WAY TO DO THIS (Assuming using the foam)?
If the answer is 'throw the foam away and use dirt' then i am OK with that - will just be a lesson learned

My next question is - with ALL Of the above images - I am losing 2 inches of depth to the sand (assuming 2 inches is the proper/desired depth of sand)
can i dish out the bottom 2 inches (evenly) and fill that with sand (Except about 1 foot around edges) and fill that with sand back to level and get the depth back?

Also i have read differing opinions on actually dishing out a deeper cup in the middle (leaving about 3 feet around edges at level) - maybe an additional 6-12 inches deep - to have a slightly deeper area in middle of pool
I do have an 'overlap' liner with the extra material (25 gauge)
Regardless of preference and additional work, are there any real downsides (or potential upsides) to having a slightly dished center assuming the liner is capable and compatible?

And FINAL question - i have about an 8 - 9 inch grade i am having to dig out (i am digging down, not filling in) - once this is done it seems there will be a 'gutter' around the pool that is a low spot for water - any mitigation for this or steps i should take on the OUTSIDE of the pool once the area is leveled?

Thanks for any help/advice - everything i have read on this site has been quality information and i have learned a lot over the last couple weeks just browsing the forums

Location - Central Georgia

-Lee

 

[phonedave]

Sand coves work just fine. There is nothing wrong with them as long as they are the correct shape (not too small). The issue is people tend to make them too small. They can also get uneven. A foam cove is consistent, the right size, faster and easier to install, and in my opinion, money well spent.

Sand goes in the pool, then the cove goes over the sand, like in your first diagram. If you are using a pad, it goes over the sand and can go under or over the cove (under make a nice looking bottom edge I think)

It is not about the sand washing out so much as it is about the liner squeezing out. Think about it. You have a giant bag of water, with a LOT of weight in it and no rigidity. Your pool is just sitting on the ground. If there is a small gap, the liner is going to start to push through that gap (kind of like a hernia). the cove turns that 90 degree corner with a potential gap in it, into two 45 degree angles, with a lot of surface area behind them.

Yes you are "loosing three inches". No you really are not. A 54" pool does not have 54" of water in it. 54" is the nominal size. Water depth is between 48-50 inches most of the time. Kind of like a 2x4 is the nominal size but the actual size is 1.5 x 3.5 inches.

You can dish the bottom out if you really want to, most liners stretch a bit, but is it really worth it? If it is not even, then it looks wonky, also if it is not even it can make vacuuming a pain, and make robots do strange things.

The overlap liner does not matter. A liner is not like a giant bag. It is two parts. A circle the size of the bottom, and a rectangle for the wall attached to the circle. there is a seam that goes around the bottom edge (hopefully smack on top of your cove). You cannot just "scootch" the liner down the wall a bit to gain more bottom depth. You want that seam right on your cove. The liners do have some stretch to them, so they will stretch into a deeper area. Some liners are made to do this, some are not. I don't see the diameter of your pool listed, but 12 inches of dish is a significant amount of stretch. I would check with my liner manufacturer for anything more than 3 inches or so.

Taper back the earth around the pool if you can. If you cannot, you can put in drainage pipe and daylight it somewhere where you (and your neighbors) will not mind the water running to.