Different Topographies Call For Different Materials
Your soil, water table, and slope decide which base and supports your inground pool needs. Here is what Royal Swimming Pools recommends for each site condition.
Every vinyl liner inground pool sits on a base troweled over the soil, under the liner. The base protects the liner and gives the pool a smooth floor. Which base you need depends on your ground, and sloped lots also need extra support.
Which pool base fits your site
Choose your base based on your ground conditions and what is available in your area.
| Your site | Recommended base | Why |
|---|---|---|
| High water table, or wet, expansive soil | Vermiculite mixed with Portland cement, or a vermiculite premix that only needs water | A porous base, and our recommendation for wet ground and high water tables |
| Rocky, dry soil | A thicker sand and cement base | Rocky ground needs a thicker base. Sand and cement is also the usual choice where vermiculite and premix are hard to find |
| Dry soil, low water table, and good drainage | Masonry sand, packed | The lowest cost option, but the softest and weakest. Mainly used for flat bottom pools. A pool bottom pad helps prevent imprints |
Only use a packed sand floor where the water table stays low. Changes in the water table can build enough pressure under the pool to break through a sand base, washing out the floor and leaving lumps of sand under the liner.
Whichever base you choose, follow the product's mixing instructions and the inground pool installation guide. Shop inground pool base material.
If water collects while you dig
Stay out of the hole while water is collecting in it. OSHA treats water in an excavation as a hazard, and its rules do not allow workers into a dig with accumulated or accumulating water unless precautions are in place, such as protection from cave-ins and removing the water.
If the water table is high enough that water fills the excavation, the excavator can stop, dig a small hole, and set a sump pump in it to remove the water.
For ongoing groundwater around the pool, HydroBlox drainage planks move water from wet areas toward drier areas without needing a downward slope. Have a construction professional assess complex groundwater conditions before installing them.
Building on a slope
On a hillside or next to a slope, we recommend a retaining wall to help with the slope. Without bracing, the weight of the slope can push on the deck, which then pushes on the pool wall.
An X-brace paired with a deck support brace helps keep both the pool and the deck level. Deck support braces are optional, and are mainly used where brick or stone coping joins a concrete deck.
The deck is usually built on a slope so water runs off onto the landscape.
Not sure what your site needs?
If you do not know your water table or soil type, contact our Sales Support team before you order so your base and bracing match your site. For a quick comparison of all four base options, see What Material Should I Use for My Pool Base? For more detail, read Different Topographies Call for Different Swimming Pool Materials and What Should I Use to Build My Swimming Pool Bottom? on our blog.
Still need help?
Didn't find the answer you were looking for? You can always contact us at support@royalswimmingpools.com or choose the category below to see our most frequently asked questions for that topic: