Is it okay to use rigid conduit, buried 6 inches, to get power to swimming pool pump and filter? The soil between the pool and house is so full of large rock that I cannot dig an 18-inch deep trench for PVC conduit without using a track-hoe. The distance from pool to house is about 25 feet and the ground is level. There currently is no deck between the house and pool. Is there another option for running the electric without an 18-inch trench that I haven't considered?

Yes, you may use steel rigid conduit buried 6 inches deep. For additional protection, you may want to have some concrete poured over the conduit, but not necessary.

Be sure to have the conduit 6 in deep to the top of the conduit.

Other items to consider:

Be sure the conduit connections are wrench tight.

Do not use any pipe dope on the threads of any electrical conduit.

Be sure to use an insulated green equipment grounding conductor.