Setting the pool in place
To set and level the pool in the excavation, use a transit and the predetermined grade for the top of the pool. A crane or excavator is then used to lower the pool into the excavation. At the same time the pool is being lowered into place, check to make sure the offsets are accurate to the project plans.
Next, mark the outside of the dig to serve as a guide to ensure that each time the pool is lifted and reset, as many times as necessary to achieve a ‘good fit,’ the pool is setting in the same place each time. Once the pool is set in the excavation, release all tension from the crane.
Then, walk along the entire pool floor to check for any voids or hang-ups. Using the transit, take readings from six different points of the pool—the four lifting points, along with the middle of the shallow and deep ends. If the pool is off by more than 13 mm (0.5 in.), remove the pool from the excavation and look at the imprint of the pool radius in the compacted floor.
If adjustments to the foundation are necessary, use a landscape rake. Also, when adding or removing compaction material, make sure to compact and feather the material to maintain a flat foundation. Investing a little more time at this juncture is worth it. The more care that is taken to set the pool properly, fewer adjustments will be required during the backfill process.
The backfill process
‘Locking in’ is the process of placing and tamping backfill around the radius of the pool to hold it firmly in place during installation. To begin this process, add 101 to 152 mm (4 to 6 in.) of water to the pool. At the same time, add 101 to 152 mm (4 to 6 in.) of compaction material to the pool’s deep end, following the water level in the pool. With the weight of the water holding the floor in position, work in a horseshoe pattern, taking transit readings up to the pool’s water level as well as 1.8 to 2.4 m (6 to 8 ft) beyond the water level. Any adjustments that need to be made at this point should be less than 13 mm (0.5 in.).
When the backfill is in place, wet it and use a lever assembly under the pool’s coping to make any minor adjustments, and compact the radius. Then, proceed with 152-mm (6-in.) lifts of backfill, again, working in a horseshoe pattern and following the water level in the pool until it is ‘locked in.’ It is imperative this process is not rushed as filling the pool with water too fast, or using an overabundance of backfill too quickly, can force the pool out of level. During this stage of the installation there is no such thing as taking too many transit readings as it is important to continuously check ‘locked in’ sections of the pool for any movement, while also checking for any adjustments that still need to be made.
Prior to installing the pool in the excavation, run the plumbing for the main drains up to return height. As backfill is compacted around the radius, leave the area around the drains open to allow visual inspections to be made for leaks once the water level covers the drain. After inspection, be cautious when compacting around the drains as damaging them could potentially cause a leak. Taking the proper amount of time to complete this process and making the correct minor adjustments is critical at this stage as a poorly or over-packed radius will cause the elevation of the pool to shift. Therefore, consistently monitoring the level with the transit will keep the installation on track.
Special attention with regards to minor adjustments and proper compaction of backfill around steps and swim outs is also critical as these areas have a tendency to droop. Before making any adjustments to these areas, make sure there is at least a couple of inches of water in the pool’s shallow end as this will keep the pool in position. Once all radiuses have been compacted, and the pool is ‘locked in,’ the flow of fill water can be increased and backfill material can be added in 152-mm (6-in.) lifts, following the water level in the pool, wetting and compacting as the installation proceeds.
