I would check the toilets for repairs, the link below should help.

: I am the owner of a seven (7) year old house, and over the past few months, a "bellowing," of sorts has started in the walls. There's not a specific incident (i.e. flushing) that causes this sound (which sounds much like a Tuba) and in fact it seems more pronounced at night. Is this just air in the pipes, or could it be something more serious that I need to have checked out?

: Thanks for your help,

: Stacie

• Titanic and Tuba toilet problems