Using selector switch to engage only one set of valves
Looking at your schematic, I don't see why it wouldn't work.


Turn SS1 to the left you get "UP", to the right you get "DOWN".
Turn SS2 to the left you get "TIPPER 1", to the right you get "TIPPER 2".


Depending on your selector switch choice your 1-2 contacts might also need to be NO. I know the Siemens ones had two plungers that pushed both sides.

My one suggestion would be a fifth interlocking contact on SS2 in line with the motor so that the motor can't run if a "TIPPER" isn't selected. If SS1 is in "UP" or "DOWN" position while SS2 is in neutral you'll dead head the pump. It may/may not like that -- pump dependent. Assuming that MS3 has something to do with the motor/pump.



Side note: seeing as this is your fourth question on EE.SE, I'd encourage you to "accept" the answers to your questions, if they've answered your question. You press the checkmark under the up/down buttons on the left of the question. Ask away though! I enjoy seeing some more automation/controls questions on EE.SE.