For years I struggled with fitted water bed sheets. Then I got a super side king regular flat sheets and for the first time the sheets stayed in. They haven slipped out and I have had them on for days. They are coming out today because I am going to wash them.
Waterbed sheets are just a rip off. No system including the pipes works at all. Get supertsize king size flat sheets and you won't have any problem
Just pin them in place.
There are elastic straps with clips on each end--specifically made for waterbeds. But I hear what you are saying. I use flat king flannel sheets on a queen waterbed. Miter and fold the ends under the corner of the mattress--they have not pulled out ever. I use a fitted Serta cotton quilted mattress cover under the sheet.
I don't have a water bed anymore. The trick I used was to take my foot and push the mattress about a half meter back from the corners. This would raise the corner high enough for me to slip the fitted sheet fully on the corners.
Let me know if this works for you.
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