If you suspect a burst pipe you will need to go through your house and turn off all the taps including all water using appliances, don’t forget to check outside too.
Next, locate your water meter and see if it is still running despite everything being turned off. The most effective way to do this is to record the black and red numbers on the meter and then wait for 5 minutes before going back to read them again. If the last numbers have changed, you have a leak and if the numbers have changed significantly, you have a large leak. Don’t forget to listen for obvious evidence of leaks such as hissing sounds or water marks on the walls or pooling on the floor. If you find a leak turn off your water and call a plumber immediately.