Is this a FRONT LOADER? Or, is this a TOP LOADER?
If this is a FRONT LOADER, the following link explains what you have to do to determine the source of a leak:http://www.fixya.com/support/r3576656-washer_leak__front_loader
In most cases on a FRONT LOADER, leaks are caused by the rubber door bellow developing small rips or tears due to age and wear. If the bellow is leaking, it must be replaced. The following link explains the steps necessary to do so:http://www.fixya.com/support/r3574186-installing_a_door_bellow_on_a_front_load
If you have a leak on a TOP LOADER, the most common cause is a worn drain pump, leaking drain hoses or the hose to the air dome has come loose. You will need to remove the exterior case of the washer to be sure. DO NOT lay the washer on its back. The gearcase contains oil and it may leak through the breather hole.
The following link explains how to inspect a TOP LOADER for leaks:http://www.fixya.com/support/r3576648-washer_leak__top_loader
If the drain pump is leaking, it is not serviceable and must be replaced, the following link explains how to replace one:http://www.fixya.com/support/r3794382-replacing_water_pump_whirlpool_top
Replacement parts (if required) may be purchased on line at any of the following websites:
Prices vary between sites, so shop and compare.
Read through the instructions provided and let me know if you need further assistance. The choice is yours if you wish to pursue this repair on your own. In my opinion, you don't need a "certified repairman" to find the source of a leak in most cases. Many of these repairs are simple with a little guidance. Please post back with a complete MODEL NUMBER so that I may be able to povide you with better assistance. I hope this help you.