methane like smell from the toilet

[ifor]

since we had a new toilet bowl and cistern plumbed in our downstairs loo by a reputable plumber; there is a methane like smell in the toilet. There are no leaks and there is always water in the pan...we do not have any pets either !!
The toilet flushes properly and there are no noises either. We have a toilet in the ensuit upstairs which is connected to the same waste pipe but there is no smell there.
any advise greatfully received
Thank you

 

[Nige F]

methane has no smell - what you are smelling is Sh** and probably the new pan is that same quality - maybe the flushing of the ensuite is drawing out the water seal in the new one`s trap - or you could have a blocked drain somewhere in the outside run

 

[RUBICON52]

Is the smell in the room or just the pan?