Need new feeder suggestions.

I currently have two PVC pipe feeders made out of 4" pipe with the "Y" fittings on the bottom. At first they worked great, but lately the chickens have decided to dig out all of the feed onto the floor.

I would like some suggestions for feeders that have worked that don't allow the chickens to dig it all out. I would like some suggestions that use PVC pipe so I can reuse some of the materials that I currently have but would consider other designs that work.

I have done a search and have seen some different versions of PVC pipe feeders but don't know which ones keep the waste down to minimum. I'm considering a version I saw here that used two upright pieces of PVC pipe using two 90 degree bends with a piece of PVC in the middle of the 90 degree bends with holes drilled in it. I never found any comments on whether the chickens were able to dig food out of this design. Thanks for any ideas or suggestions.

Wayne