Although the joint seems strong within 60 seconds, the “glue†is still not dry. I try to wait at least an hour, or more. For a joint with a cycolac (ABS) fitting like a Hayward union, the cycolac/ABS takes longer to set. PVC “glue†is not really a normal glue, but a solvent welding glue that dissolves the materials and allows them to bond as the materials reform and dry. For ABS I wait several hours. Putting water pressure on joints too soon can cause them to separate or leak.