Choosing a Relay to Operate Solenoid Valve
VA of 25 is only 1+ Amp at 24V but considering turn off arc, I would use 5A non gold plated contacts using an optoisolator driving 10mA from 3V (e.g. some require selection of series R for preferred IR current. ) with  decoupling cap on 24V supply on Relay board for EMI reduction.

These are cheap (2$) and optoisolated as well in 5,12,24V types with many current ratings.

I suggest a 5A Relay but photo shows 25A ($2 on ee bae )



Or this multichannel one for future expansion/

It is not a 3V sensor but 5V.

THe sensor is 5V PNP &lt;100mA pullup compatible with 5V Opto drivers for 15~20mA for high side drive with built in R on Relay cards that are PNP or NPN compatible.

http://www.ebay.ca/itm/OMRON-4-Channel-5V-Relay-Module-Opto-couple-For-Arduino-UNO-Mega-R3-AVR-ARM-/301286279825?hash=item46260fca91:g:RIsAAOSwgkRVVBzK

This one is better with many sources to buy.




  Use suitable twisted pair for all drive pairs for improved EMI control.
  OMRON makes high quality relays. 


Reverse diode clamp across output contacts are necessary to prevent high voltage impulse voltage with solenoid loads on turn off.  (1N400x or equiv.)