Hi Jean, Thetford make a few different models of toilets and pumps. If you take out your casette the model number is often found on that. Next the good news, Thetford have a good supply of spares at many good caravan spares outlets, although they are not all that cheap.  Most spares come with a leaflet on how to fit and are usually straight forward with a minimum amount of tools.  I suggest you go for it, you may be supprised on how easy the job goes. Good Luck
                 bostonden
                
 March 2010