Getting a 1/2"pvc pipe to fit a 1/2"pvc coupling

[PtrJack]

I have seen people speaking of this and others not understanding. I have a leak in my pipe coming from the main. Attaching a new 1/2" coupling to the 1/2" pipe (blue pipe) is a problem as the coupling is larger than the pipe although both are 1/2".
Most people do not realize that there are Chinese made pipes that are off. There are also other pipes that do not make a tight fit. I do not want to jack hammer the ground and change the pipe. All I want to do is put a coupling on the pipe. Is there a way using perhaps water seal or anything that can give me a tight fit?

 

[Brambles]

If you are in the UK use the appropriate size of Plasson connector - all decent Plumbers Merchants stock them