Collapsed sewer pipe

Our development has been more or less completed by the builder but through a series of sewerage back ups we have discovered that one of the sewer pipes serving the devt has collapsed . Builder has says they will get it fixed. I dont really trust them as they are typical buiders ...Question is
are they reponsible for it until the devt is handed over to Co Council ?
will Co council check sewers drains before they take it over ?

The Local authoritity will generally insist on the developer furnishing a survey of the drains and services, which will include a CCTV survey of the sewer runs- this will obviously highlight any defects like that you have mentioned. When the developer applies to the local authority to have the development taken in charge the developer will be required to place a public notice to this effect in the national press or a local paper. You will have an opportunity to make a written observation at this stage, should any other contentious issues arise.