Push Fit pipe in freezing conditions

I want to run 3 pipes down to my outhouse at the bottom of the garden, about 16m from my house. Approx 6m of the run is above ground, along the edge of my patio, and the rest I can lay beneath a flowerbed.
The pipes are for hot, cold and drain water (pumped back up the garden from a small underground tank using a powerful pond pump).
I was thinking of enclosing 3 PE-X push fit pipes inside a square rainwater downspout pipe, all readily available at the DIY store.
Does this sound like a reasonable idea? Anybody know if PE-X pipe would withstand the water inside freezing?
Cheers James
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