Why not ?
tell them the price you would be willing to do it for , " every body has a price " dont they ?
Then its simple case of yes or no , I had a very simillar situatation a cple years ago, diahorrea went from bedroom along landing to bathroom, my price was £300 take it or leave it and i even said would prob be cheaper to get a new carpet, No dont want the hassle jobs yours .
an hrs work half hr flushing machine and tools, £300 in my pocket, ets be straight here your a c/c you will come across situations like this, all part of the service in my opinion.

Geoff