As already stated, Pushfit fittings should not be used on Chrome Plated Copper or Stainless Steel tube. The surface is too hard for the teeth to grip and over time will slide off.
I always connect plastic pipe to Chrome pipe with a compression fitting, I have seen the Chrome plating removed by a file and a Pushfit fitting used directly.
From a warranty point of view, I think you are better covered by using a compression fitting.
Again as already stated, all the major Pushfit makers say not to use their fittings on CP pipe, so you would have no come back with them.
Edit. Regarding pressures, most Combi boilers "Blow Off" at 3 bar, depending on what make of Pushfit you go for the recommended test pressures range from 1.5 times working pressure to 18 bar, so if fitted correctly they shouldn't blow off.
I always connect plastic pipe to Chrome pipe with a compression fitting, I have seen the Chrome plating removed by a file and a Pushfit fitting used directly.
From a warranty point of view, I think you are better covered by using a compression fitting.
Again as already stated, all the major Pushfit makers say not to use their fittings on CP pipe, so you would have no come back with them.
Edit. Regarding pressures, most Combi boilers "Blow Off" at 3 bar, depending on what make of Pushfit you go for the recommended test pressures range from 1.5 times working pressure to 18 bar, so if fitted correctly they shouldn't blow off.
