The most typical symptom is a water backup. Water will back up from your floor drains or cease to drain in sinks or bathtubs. Toilets not flushing properly as well as gurgling sounds or odours coming from your drains are also signs you may have a problem forming.
Many people don't take action until it is too late. If your sink or bath empties slowly you should consider taking action before a more serious problem occurs such as flooding. If you have tried pouring hot water down your sink or using a pipe snake to clear more local blockages and the problem still persists then get in touch and we'll be happy to help and advise on further action.