How do you find plans for water purifier?

[HotShot]

Also, is there any way to get food that doesn't give you radiation or can you build a radiation shower to cure yourself?

[Bobby Digital™]

there is the leadbelly perk that can completely remove radiation from all food and drink at rank 3.

there is a radiation shower to build, i'm still trying to build one myself. from what i have been able to find, you can randomly be awarded the plan for it during end-game scorch beast killing. perhaps a later commenter will be able to answer about the decontamination shower.

[RMPyro]

The plans for building the industrial water purifier can be located at Camp McClintock in the overseer's cache.
The plans for building the normal water purifier can be located at Charleston Capitol Building in the overseer's cache, just inside the doors of the Charleston Capitol DMV.

For food, allways carry radaway with you. You get plenty of them from quests.

[Stardustfire]

before the legendary perks the decontamination ark was useful, its plan drops from queen event, but since legendary skills are out its useless, just take "what rad" and never again care for any radiation that isnt a dropzone or the harvesting zone of radiation rumble...

for the water purifiers, like already mentationed above you get them from different overseer staches, and for generators, that you get from completing events where you get the powerplants running again. solar panel and vault tek generator plans are from Daily Ops when you participate in them with a char over lvl 49 (under lvl 50 you dont get the special reward plans but other, more basic, plans instead)