the internal bore of the flexy is much less tho, and some are better than others. Those looks like JG ones, so the hose is only 13mm inside.
Whilst eg BES item 13753 is compression, it's also 19mm bore, much better flow
I went with a similar but cheaper option that controls right down to (IIRC) 25c and has an integrated bypass and inlet restrictor ( there's a more basic one without, bit using the same thermohead I think)
https://www.amazon.co.uk/Universal-Underfloor-Heating-Thermostatic-without/dp/B076KK1KQF/ref=sr_1_119?dchild=1&keywords=underfloor+pump&qid=1594565525&sr=8-119
Now I'm gonna strip a connector today to confirm it to myself but it's my belief that the collet doesnt get "done up" on the white domestic stuff. The collet bites into the pipe automatically and grips tighter as line pressure increases like with any pushfit. All the twist does is move the outer stop such that the collet won't depress surely?
The horseshoe clip has been used as a positive *lock* for years on the beige and black systems.
regardless I'm still waiting to hear exactly what has been happening to cause Nick's comment: " the crap design from undoing and flooding your house "...
no, the rotate bit disables the collet in the same way as the horseshoe stop.
So why have I been successfully just pushing pipe into fitting-s per the MIs- of mission critical fittings for years and (other than pipe collapse of vinyl and nylon pressure tube and hardening of O-rings) never see leak or failure?
Nick, I've been around JG and their collets for what? 30 years on gas air and fluid systems. How come you see problems with their domestic water fittings that don't occur anywhere else? How do these fittings leak? If it's fully inserted and under pressure, the pipe aint coming out...