installing pool on unlevel ground need advice

[mwatson61]

I have a frame built out of 2x6 that is level across the top, but 5"deep on one end and slopes down to about 11 inches on the opposite (long) end on the ground surface itself. I was thinking of using all masonry sand for backfill. which would make the underneath of the sand pad un-level but the top would be level. after reading some posts, everyone talks about only 2" of sand for a base. I need some ideas on what to do in this case. I read one that said use unwashed gravel to level unevenness and then top it off with sand, water and tamp several times. This is my first install and I don't want to have to redo it. The frame work is 2 feet or better all the way around the pool dimensions. Please help

[PoolDoc]

. . . membership upgraded.


I'm sorry, but I can't visualize what you're describing. I can tell you that a edge supported 2x6 wood frame is not going to be adequate to support anything but a tiny pool. This 16' Intex Ultra pool (http://www.amazon.com/exec/obidos/ASIN/B000XU0IQ8/scouscho-20/) will weigh 15,500 lbs or 7.7 tons when filled.

[CarlD]

I can visualize it. I just can't visualize it supporting the weight.

If I remember correctly there are some rules of thumb for a built-up base if you don't have it engineered. Like, if the pool is 16 feet wide and your base is 1' high, the base needs to be 2' wider than the pool on both sides--or 20' wide. If the base is 2' high, it needs to be 4' wider than the pool on each side, or 24' wide. And that's when you use retaining wall block.

[mwatson61]

after I took out the grass with the sod cutter I did not realize how unlevel the yard was in that spot on the one end, it took out so much that the top of the frame is about even with the original grass line and I thought that the back fill of dirt on the outside of the frame would help support the walls of the base plus I plan on staking the outside of the frame every 12" all the way around. as far as the base the recommended clearance area is 25 x 34. that includes the area for the area support legs on each side. I made the frame 26 x 37 to allow enough room all the around. the original suggested clearance was only allowing 6" around the pool itself and I thought it was not enough to support the weight so I just made it bigger. what my concern is having to much sand in the one end and it allowing the pool to shift when it gets full. the pool I am installing is the deluxe 8000 18 x 33. so I pulled the spec sheet off the website to get started on the base and I now I am at a stopping point because if I dig out the high spot to meet the low spot my pool would be lower than the grass line by about 8 inches. very concerned............

[BigDave]

What kind of pool? Traditional steel wall Above Ground or soft sided?

[mwatson61]

traditional steel wall

[BigDave]

The sand really goes inside the pool wall - the wall holds it in.
You are right, sand can shift. I have also seen the 45 degree rule CarlD mentioned.
It's best to dig down to undisturbed soil, if you must build up, a block retaining wall filled with compacted base material (crushed concrete comes to mind) would be the way to go.
You can also dig to level then hold the high side back with a retaining wall. You'll probably have to dig quite a bit larger than you already have to build the wall.

[CarlD]

A popular material up here for filling, like BigDave's crushed concrete is called Quarry Product, known to the trades as "QP". QP is dirty large gravel. It's unwashed and has fairly large chunks of stone (1") mixed with dirt. It's significantly less expensive than washed gravel, drains virtually as well, and has a very high friction coefficient which makes it less prone to shifting under the immense weight of a pool. It's really one of the best products for backfilling behind retaining walls.

My base rises about 2 1/2' at the ground's lowest point and using QP and retaining block (and an engineer :) ) I was able to make the base smaller than the rule of thumb. It hasn't shifted at all in 12 years.

If you REALLY want to ensure it works great, install a French Drain first, underneath it to drain away any water that passes through the QP.