there is 2 types of pvc pipe solid & pourous, i use the solid for hollow tree stumps layed flat on the bottom for these i stand them up & mix a sack of ready mix concrete & fill the bottom 2-3 inches to close them off for catfish breeding. i use the pourous schedule pipe for trees standing upright. fill bottom ft of main pipe which makes it sink but the pourous pipe floats so even if it tips over it floats back up.kinda like weebles wobble but they dont fall down. LOL!! easy to tell difference between 2 types of pipe just look at the end after you cut it & if your still not sure just throw it in the water.
