What maximum slope is allowed when covering the liner with sand/gravel/clay to prevent the material from sliding down the slope?

For optimal results, we recommend a maximum slope of 6 to 1 (over 6, down 1) if there is no geotextile fabric installed over the liner. A slope steeper than this may result in the ballast material (such as sand, gravel, or soil) sliding down the liner towards the middle of the pond. However, by adding a geotextile fabric over the liner, slightly steeper slopes can be achieved with less issues. The fabric provides additional grip and protection, helping to keep the ballast material in place and prevent any potential sliding. With the right slope and geotextile fabric, you can create a pond that is not only beautiful, but also functional and long-lasting. You may be able to achieve a steeper slope (4 to 1) by creating a speed bump. Larger rocks will hold the slope better if they can be locked together with waterfall foam or concrete grout. Find our Geotextile Underlay here:  geotextile.