Grey pipe for exhaust? Can 636 white pipe being glued to the grey pipe?
Some of these instant hot water/combi boilers require a certain minimum footage of cpvc leaving the exhaust of the appliance. If the orange cpvc glue is used to join the grey to white, it's fine since it's approved for use with both. It looks like royal in the picture, but I assume the same rules and glues exist. The owners manual should mention this.