Fitting a Blanking Cap to a redundant waste pipe

[Dark Eyes]

Hello folks

I have what seems to be a standard 40mm white PVC pipe that used to hold the washing machine drain hose, which I wanted to cap off to avoid any water overflowing from (as my kitchen drainage seem to get blocked up easily, and it will probably be replaced within the next year).
I bought a McAlpine T23U as, according to Wickes it fits a 40mm pipe, but it seems very loose on the end of the pipe. I notice from McAlpine's technical drawing https://mcalpineplumbing.com/sites/default/files/uploads/drawings/T23U.pdf that it shows a 44.5mm internal diameter for the cap, which explains why it feels loose.
Have I bought the wrong thing, or should I have glued/siliconed the end of the pipe into the cap ?

 

[ShaunCorbs]

Have you tightened the fitting ?

 

[snowhead]

Check that you haven't pushed the seal into the bottom of the cap.

 

[Dark Eyes]

I have taken it off and put it back on,and it feels tighter now, so hopefully it is now water tight.