If you suspect you have a plumbing leak in your crawlspace, You should determine if the source is the water supply system or a drain. If the leak is in the water supply system – shut off the water to the house immediately. If it is a drain, stop using the fixture(s) connected to the drain – shut off the water to the fixture(s). Call your plumber immediately in either case. Due to health and safety reasons you may need to also call a specialty pumping or remediation service.