Sump Pump drain tile

We need to update our sump pump drain tile. We currently have a 4 inch perforated drain tile extending 20 feet from the discharge point outside the house. The tile is now just underneath the sod and the end of the drain is not buried. It is draining above the sod and our land has sunk at that point.

Is 4 inches OK and how deep should we rebury the drain tile and should it be at the same depth all the way to the end?

I take that you are speaking of the sump pump discharge piping, not the sump intake drain tile...

Theoretically, the discharge can be at any level in relation to the surface. The important part is the downward slope away from the house. You should check with your inspector as to the minimum slope for 4" drainage pipe in your area. This will vary by location due to concerns with ice/freezing.

Water tends to move horizontally below the subsurface. If the perforated pipe is too close to your foundation, you may be recirculating water back to the sump. Your goal should be move all the water as far as possible from your house, preferably to a drainage ditch or if legal, a storm drain. You can also install a tile in the low spot to move the water on to a better drainage point.