Whether you have a front- or top-load washing machine, it has a drain pump, and malfunctions of that pump are behind many draining issues. This essential component may be directly connected to the motor that runs the agitator, it may be belt-driven or -- in front-load models -- it may be powered independently of the drive motor. The problem is often a clog in the pump or the hoses leading to and from it or a malfunction of the pump itself. The problem could also be a faulty switch or blocked coin trap.
Coin Catcher and Drain Hoses
In most cases, you will have to look inside the washing machine to find blockages or diagnose problems with the drain pump. Before you remove the cover, though, there are two things to check: the coin catcher and the drain hoses behind the machine.
Not all washing machines have coin catchers, but if yours does, it's located behind a small door on the front or side panel. Open the door, pull out the filter and remove anything you find there. Look inside the door with a flashlight -- there may be a sock or some other clothing item blocking the pipe. Remove anything you find. After checking the coin catcher, pull the machine away from the wall and check the drain hoses for kinks. Straighten any you find.
Defective Lid or Door Switch
If you can't find any blockages, the lid or door switch may be malfunctioning. The switch is a safety device that prevents the washer from operating when the lid or door is open. If you suspect a faulty switch, you can check it by unplugging the washer, disconnecting the switch and testing continuity with an ohmmeter. Replace the switch if the test shows high resistance across it.
Drain Pump Problems
Always unplug the washing machine before removing the cover or back plate to inspect the drain pump. Which of these you need to remove -- as well as the procedure for doing it -- depends on your make and model, so check the manual on the manufacturer's website first. The drain pump could be located near the front or back of the appliance, and it's always near the floor.
The drain pump may be working properly, and the draining issue may be caused by a blockage. Whether the pump is belt- or direct-drive, or it works independently, it always has an inlet and an outlet hose. Loosen the clamps securing these hoses, remove them and check inside for small items, such as socks, underwear or children's clothing. Remove these blockages.
It's also possible that something is stuck in the pump itself; if so, you can often see it, since most pumps are made from translucent plastic. Retrieve it with a screwdriver or pliers.
One more thing to look for is kinks in the internal drain hoses -- if you see a hose that you can't easily unkink, replace it.
Check the Pump Operation
If you don't see any blockage, the pump itself may be faulty, and the method of checking depends on what type it is.
Direct-drive pump: Unscrew the pump from its mountings, pull it off the motor shaft and turn the impellers by hand to make sure they move freely and that none are broken. Replace it if it's damaged.
Belt-driven pump: Besides checking the operation of the pump itself, which includes making sure it spins freely and has no broken impellers, check the condition of the belt that drives it. Replace the belt if it's glazed-looking, which indicates that it's probably slipping.
Independently-driven pump: Many front-loaders have an electric pump powered by a dedicated circuit in the machine. Check the connections to make sure they are tight. In some cases, you may need to test the pump with an outside power source, but it's best to get a qualified technician to do this.