Plumbing - Pipes groaning

[Bobster-cyw]

Recently, whenever we flush out toilet there is lots of noise, it sounds almost like a fog horn going off. I'm assuming it's got something to do with the water/pipes but dont know if its something I should worry about or would be able to fix.

Has anyone come across this or know what the cause / solution is ?

thanks

[ianmunt]

We've had similar noises caused when a valve washer vibrates.,Could be that the washer needs replacing

[sddsddean]

Sounds like water hammer. Have a look at this.
http://www.simplifydiy.com/plumbing-and-heatin g/mains-water-systems/water-hammer

[jocky]

Yep... deffo sounds like water hammer, check the pipework going to the cistern is secure.