Washer Not Draining: What a Technician Tests, From Pump to Standpipe

A washer that stops with gray water in the drum has a drain problem somewhere between the tub and the building’s sewer line, and only part of that path is inside the machine. A technician works through it in a fixed order: what the control thinks is happening, whether the pump is getting power, whether the pump can move water, and whether the house can take the water once it leaves. Below is that order, with the readings we look for and the places where a wrong guess costs money. It is written the way we train new technicians, so it assumes a meter, the tech sheet and some experience with live appliances.

Most of the work on this call happens with water still in the tub, which is what makes it harder than it looks. The water has to come out before anything can be replaced, and on a front-loader the only way out is usually through the same pump that stopped working.

What a technician brings to this call

• A digital multimeter rated CAT III with good leads, and a non-contact voltage tester.
• A wet vacuum, a low flat pan, and several towels. A front-loader stopped mid-cycle can hold several gallons above the filter, far more than a baking dish can take.
• A length of 1-inch hose and a bucket for draining through the emergency drain tube where the model has one.
• Nut drivers, Torx T20 and T25, and a putty knife for the clips on Whirlpool-built top panels.
• The tech sheet. It lists the service-mode button sequence, the pump test, and the error codes for that model. Without the sequence you cannot command the pump on by itself.

Read the code and the tech sheet before opening anything

Electronic washers watch how long the water level takes to fall. When it does not fall in time, the control stops the cycle and stores a code. That code names a symptom, a slow drain, and a slow drain has at least five causes. It is still the first thing to read, because it rules out the machines that stopped for a different reason and only look like drain failures.

The tech sheet matters for another reason. On most electronic washers you can only test the pump properly from service mode, where the control runs the drain pump on command with no fill and no spin. The button sequence differs by model family and sometimes by year. Guessing at it on a Samsung or LG can start a calibration routine you did not want.

Step 1: get the water out without making it worse

Nothing gets diagnosed with a tub full of water. How the water comes out depends on the machine.

On front-loaders from LG, Samsung, Whirlpool, Maytag, Electrolux and Bosch, a small access door at the lower front hides the pump filter, sometimes called the coin trap. Many have a thin emergency drain tube next to it. A technician drains through that tube first, into a low pan, a little at a time, because the filter cap releases everything at once and the floor takes whatever the pan cannot. Only then does the filter come out, turned slowly counterclockwise. On a stacked pair in a condo closet, there is often not enough room to get a pan under the access door, and this step alone becomes a two-person job.

Top-loaders usually have no front filter. The water comes out through the drain hose, lowered into a bucket below the level of the tub, or with a wet vacuum from the top. Whirlpool-built direct-drive top-loaders from before about 2010 have a pump driven off the motor, reached from the back of the cabinet. Many GE top-loaders put the pump underneath, reached by tipping the machine back.

Whatever comes out of the filter tells you something. Coins, hair ties, underwire, sand from beach towels and lint felt are the usual finds, and a filter packed with them explains the code. A clean filter does not clear the pump. It moves the search upstream to the pump itself, or downstream to the hose and the house drain.

Step 2: is the pump getting power?

This is the test that separates a bad pump from a pump that was never told to run. With the water out and the cabinet open, the technician puts the washer into service mode, commands the drain pump on, and reads voltage at the pump connector while it should be running.

A few newer LG and Samsung platforms drive a DC pump from the main board. On those, the voltage at the pump is not 120 V AC, and the expected reading comes only from that model’s service manual. Reading a DC pump with the meter on AC gives a number that looks like a failure and is not one.

The 0-volt result is where boards get replaced unnecessarily. Before blaming the control, the technician follows the harness from the board to the pump, because on front-loaders it runs along the bottom of the cabinet where water and mice reach it. A board that does read output on the pump pins and loses it at the pump connector has a wiring problem, and the board is fine.

Step 3: the pump with the power off

Unplug the washer and confirm it is dead with the non-contact tester. Take the connector off the pump before measuring, so the meter reads only the pump.

• Most AC drain pumps on current LG, Samsung and Whirlpool front-loaders read in the low tens of ohms across the two terminals. Some pumps from other makers read higher. The exact value is on the tech sheet. OL means an open winding and a dead pump. A reading close to zero means a shorted winding, which can also take out the board output that feeds it.
• With the filter out, a technician turns the impeller with a finger or a plastic tool. Most synchronous pumps have a little free play before the magnet engages, then turn with even resistance. A gritty feel, a hard stop, or an impeller that spins with no resistance at all is a failed pump even when the winding reads fine.
• Any continuity from a pump terminal to the pump body or the cabinet means water has reached the winding.

A pump that passes all three can still fail under load. A worn bearing drags once the pump warms up, and the drain slows after a few minutes. That is why the final test is a full drain under service mode with a timed flow, not a resistance reading.

Step 4: the water level sensor and its air hose

The control decides the tub is empty by reading air pressure. A small hose runs from an air chamber at the bottom of the tub up to the pressure switch or water level sensor near the top of the cabinet. As water drains, the pressure in that hose drops and the sensor reports a lower level.

If that hose is kinked, split, or has a drop of water or soap scum sitting in a low point, the sensor keeps reporting water that is not there. The pump runs, the tub empties, and the control still throws a drain code because it never sees the level fall. This case fools a lot of people, because everything they can see works.

Older mechanical pressure switches can be checked for continuity between terminals as a technician blows gently into the port. Electronic sensors on Samsung, LG and newer Whirlpool washers report a frequency that the board reads, and a resistance reading tells you almost nothing about them. On those, the technician reads the level value in service mode with the tub empty and compares it to the empty-tub number on the tech sheet. A sensor that reads full on an empty tub is either the sensor or the air chamber, and the chamber gets cleaned before the sensor is replaced.

Step 5: the drain hose, the standpipe and the house

If the pump runs and the water still will not leave, the problem may not be the washer at all. This is the part of the call where a technician measures the installation against the manufacturer’s installation instructions.

In condos and older apartment buildings the laundry standpipe often ties into a shared stack. When that stack slows down, every washer on the line drains slower, and the one with the weakest pump throws a code first. The test is simple and tells you a lot: with the washer off, the technician pours a bucket of water into the standpipe at about the speed a pump delivers it. If the standpipe backs up, the washer is not the problem, and the fix is a plumber or the building’s maintenance staff.

Step 6: interlocks and the control

A front-loader keeps its door locked whenever water is in the drum. If the lock or its switch reports a fault mid-cycle, some controls abort with water still in the tub, and the cycle ends looking like a drain failure. Samsung dC or dE, Whirlpool F5 codes and LG dE point here. The lock is tested by reading the lock-confirm circuit in service mode, which again is a live test.

The main control board is last on the list for a reason. A board that has lost its pump output looks exactly like a dead pump from the outside, and so does a chafed harness. The board gets replaced only after Step 2 shows no output at the board pins, with the harness tested end to end. Boards on Samsung and LG front-loaders often follow a storm surge in South Florida, and if the washer started acting up after a nearby lightning strike, the technician checks for other failed loads on the same board before quoting it.

Reassembly and the test that confirms it

• The pump filter goes back with its O-ring seated and lightly lubricated with water, hand tight. A cross-threaded filter leaks slowly onto the floor and is noticed weeks later.
• Hose clamps on the pump go back in their original orientation, away from the cabinet edge, so they do not chafe the hose on spin.
• The pressure hose is routed with no low points where water can sit.
• The drain hose goes into the standpipe to the depth the instructions allow and is secured with the clip, not tape.
• The test is a full rinse and spin with a timed drain, watched at the standpipe, followed by a check of the floor under the pump.

What our technician does on a drain call, and what it costs

Code and service-mode history, a controlled drain of the tub, voltage at the pump with the pump commanded on, the pump and sensor tested off power, then the hose, the standpipe and the house drain. Typical South Florida prices with parts and labor, from our current price pages:

• Pump filter clearing and manual drain: $120 to $180
• Drain pump replacement: $180 to $340
• Water level sensor or pressure switch: $150 to $260
• Door lock assembly: $180 to $340
• Main control board: $240 to $520 depending on the model, quoted only after everything cheaper has tested good

We repair every washer brand across Miami-Dade, Broward and Palm Beach, seven days a week. The service call is $59 and it is credited to the repair when you go ahead. Call (754) 345-4515, or see washer repair and front-load washer repair. Brand pages: LG, Samsung, Whirlpool, Maytag, GE. If the code on your display is not a drain code, start with washer error codes explained, and if the tub drains but the clothes stay wet, read washer not spinning.

Questions owners ask