Damp smell, but no obvious damp? Help

[mugcup]

We moved house last year, house had 'library smell' as we called it in the hall. We are here a year and had it painted, new carpet etc but this damp smell is still here. The other day we had a bad leak under kitchen sink and that particular cupboard smells of damp so I've stuck dehumidifiers in to help but I can't understand why I can smell strong damp, 'library' smell in hall and how the hell to get rid of it?!?

Suggestions welcome

Probably rotten wood from a previous leak long term leak. Needs stripping out otherwise it will just continue to smell.

A leak on the incoming water supply pipe under the house draining into the sub soil below the foundations.

@honkeytonkwoman38 it would definitely make sense but I can't understand how a leak would have happened in the hall but I admit I know nothing about pipes etc . There's no silverfish (that I've ever noticed and we had them in a previous rented house )

@MrsMoastyToasty oh gosh! How would I find this out? Would I literally need to rip up floor and see?

@mugcup

1. Lift floorboards and look into the void space below the house with a torch (obviously can't do this with a concrete floor)
2. If you're on a meter, turn everything off in the house and then go outside to the meter and see if there's any movement on the dial.