Thermowell seal

Just installed my brewpi thermowell on to my kettle. There is a small leak coming through to the outside. I have tightened it now which has reduced the leak and it is sufficiently tight now to have pulled the ‘roundness’ of the kettle wall flat i.e. the kettle wall is slightly deformed by the fitting.

I am reluctant to tighten it any further. Should I have used PTFE on the thread?

Thanks

Yes, you should use a bit of Teflon tape. The only place it could leak is through the thread. Hole size should be 21mm

Thank you Elco. It was only a very tiny leak but now stopped with a few wraps of tape.