Changing the valve without killing the pump

[Maestro]

My PB put the fear of God in me to never, ever change the lever on my sand filter (filter, backwash, rinse, etc.) without turning off the pump first. What about changing the valve position from skimmer to main drains or vice versa - can I do that while the pump is running?

 

[gtemkin]

Yes, it's generally OK to switch a 3-way valve (T shaped) from skimmer to main drain and vice versa so long as the skimmer isn't blocked by things like toys, balls or low water level and the main drain isn't blocked by anything (sunken inflatable raft??).

 

[cowboycasey]

do it very s l o w to let it equalize and you should be good