Paul/Anthony,
If the sprinklers are being pulled out of the ground, I suspectthat the
feeder tube (6mm spaghetti, as I recall) is far too short! There should
be sufficient tube to allow the main line to move up to 200mm each
direction. We put in sprinklers with 600mm of feeder tube attached.
There has not been one, in the almost 10 years they've been in, that has
even moved a srinkler, let alone pull it from the ground! (And, being in
Tamworth NSW Au, we get some fairly warm days - yesterday was 37, and
today is tipped to be the same!)

Advice, get a roll of the feeder tube (we sourced ours from Water
Dynamics - used to be Southern Cross) and use a decent length of it to
feed the sprays.

Cheers
John Attwood
Tamworth NSW Au