Sinking A Trampoline
There are pros and cons when considering to sink the trampoline into the ground. The trampoline is less visible and it provides easy access on and off the trampoline. If anyone was to fall from the trampoline the height is reduced. Decide whether you want the trampoline just above or flush with the ground. It is difficult for air underneath compressed by bouncing to escape through the tight mesh of a polypropylene jumping bed. This affects and inhibits the bounce.The options are either:
To set the trampoline bed 6" above the ground, allowing the air to escape under the top rail, or by constructing underground air vents. Using flexible plastic pipe, these need to lead to the surface, where they can be concealed in a suitable site.
Trampolines with a 2-string bed can be positioned flush with the ground as the air passes freely through them.
You need to ensure that your trampoline is stable once positioned in the pit.
You don't want the trampoline to start tilting after a few weeks so this may require a concrete floor, depending on your local soil conditions. If so, you will need guards to protect the feet of the trampoline to prevent damage, corrosion and the trampoline slipping.
It is important that there isn't a gap between the edge of the trampoline and the ground large enough for a child's ankle or wrist to get trapped in.
Make sure your pit does not collect water when it rains. Clay soil can be a problem. A trampoline/pond combination is not desirable!