This is probably fairly unnecessary, but a fun project. Run three softish silicon hoses through this and it will clamp two out of three of them at any time, using the servo to choose which one is open. This way you only need one pump for three pots. The construction is self-locking without screws, although you may want to use screws to fasten the servo. I used a "standard" servo, equivalent to a Futaba S3003.
I printed this with cheap ABS.
A very simple hose clamp for the edge of a pot is included as well, as a separate part.

Ultimaker

Ultimaker 2

No

Yes

0.06mm

44%

This should be printable with minimal supports. Print three pegs, and one of each other part. The pegs should fit nicely without post-processing.

Put the three pegs into the corresponding holes in the casing, with the rounded ends towards the outside.rnMount the rotor on the servo, after putting the servo in its middle position. If you lay the servo down with the axis pointing away from you, and positioned so that the axis is on the right-hand side, the rotor should be mounted so that the thinner section is pointing straight up.rnThen mount the servo on the servo mount, and slide the mount into the slot while guiding the rotor into the housing.rnPut the whole thing in the outer housing to lock it together.rnNow insert one hose at a time, moving the servo to the correct position for each one to open the hole.rn

This was done in OpenSCAD. Unfortunately, the code is too messy for me to want to share it.