I am having an issue with relays sticking
Your relay contacts need a snubber and/or MOV/TVS to suppress the inductive spike when switching an AC inductive load (your valve). Without the suppression, the resulting arc can cause the contacts to "stick" (weld).


(Image from Red Lion SNUB0000 datasheet)

If your load were DC, a diode across the coil would be the more common solution.

See also https://electronics.stackexchange.com/a/100139/25328