Omnifluid removes fluid water and used solid water. this normally works without problems. but your watertower can not be changed I think, because it is based on a fluid tank and may be the inner logic need fluid wasser at present.
Could you work togther with the creator of with https://mods.factorio.com/mod/omnimatter_fluid to find a solution?
I have already made a request in their discord.
Request: https://discord.com/channels/351216213327609858/351216542400249856/1171519594498899978
Server: https://discord.gg/y42ZAaJZ

Happy to discuss this, but I can't promise compatibility in this case. I'll join their discord.

The most complicated thing is to find out who needs to adjust something. ;-)
omnifluid cannot change your water tower if it is a fluid tank, then you need to check if omnifluid is present and provide a water tower based on a chest, only as example.

I created an issue for it, but I'm not sure when I'll get to implementing it: https://github.com/bahrmichael/factorio-tycoon/issues/220