Thiscould be because the pump is a “flooded suction” and the water from the pool isdraining into the
strainer basket, making lid replacement very difficult.Verify that the pump is off.
The hose from the skimmer to the pump can have avalve installed to shut off the water or plug the
skimmer until you can get thelid back on.
With a flooded suction there should ideally be a valve at theskimmer and one at the return port.
This enables you to isolate the plumbingsystem and work on it without water draining from the pool.
Withvalves on the system, you must remember to open them when work is completed, sothe pump
motor does not burn out from lack of water.