I have been sleeping on a king size water bed for going on twenty years.  The wife does not care for it a whole lot.  I thought I would see if it is possible to drop in a regular mattress since the bed itself is a nice piece of furniture.  I understand a California king or a Western king mattress will drop right in.
Has anyone done this or can verify this is true before I drop a grand on a mattress that I may or may not be able to use?

How about getting a mattress pad for her side..
I sometimes sleep with my camping pad on to of my waterbed mattress---for those nights when you really need a little firmness......back problems anyone?

We switched from a waterbed to a regular mattress 5 years ago. We simply bought a whole new solid oak bedroom set for our room. The waterbed was still in good shape and had a really nice headboard, too, so I just chopped up the side rails and footboard and made them into a stand to convert the headboard to a freestanding piece. Then I bought a frame and mattress set, bolted it to the headboard, and put it in the room of one of my daughters. Great way to re-use the old waterbed frame.

I have a California king waterbed, all wood, headboard, drawers in the sides, etc.  I just dropped a Cali king size regular mattress in.  No problem.  No alterations at all.  It fit right inside the sideboards.

Dan, ditto what LarryG said.  We did it last year and were able to leave the rails in place.  It was a perfect fit.

LARRYG & Fox,

That's exactly what I needed to know.

Thanks