No rocket science here. A fair amount of our work involves troubleshooting dry fire hydrant and fire hydrant problems and developing recommendations/plans for repair or replacement. For dry fire hydrant suction heads, a common issue with the PVC/metal heads is failure of the sealant or gasket where the metal head is threaded into the PVC fitting. Some times this is production QC and sometimes it is just wear and tear from the FD guys beating on the fitting with a big hammer. An easy way to troubleshoot the, "We can't get a draft" statement from the FD is to put a pumper on the DFH, gravity feed water back into the suction pipe and see if water drips at the connection. If the hose connection is tight and water drips....well, that right there is the problem. Probably just best to replace the suction head with a new one.