Bosch Dryer Not Draining: Let the Error Code Lead

A Bosch ventless dryer that won't drain is almost always a blocked pump impeller, a kinked or clogged drain hose, or a stuck tank float — and the error code tells you which family you're in. E:08 points at the tank and its float sensor; E:18 points at the pump and the drain path. Start by reading the code, then listen for the pump.

Know the Drain System You're Diagnosing#

A heat-pump or condenser Bosch dryer pulls water out of your laundry and has to move it somewhere. That job falls to a small condensate system: a sump that collects the water, a pump that lifts it, tubing to either the removable tank or a plumbed drain, and float sensors watching the levels. When any link jams, the dryer stops and posts a code — E:08 for a full tank, E:18 for a drain timeout. Those two codes cut your search in half before you touch a screwdriver.

Read the Code, Then Listen#

Two quick observations do most of the work. First, the code: E:08 means the machine believes the tank is full, so the fault is the tank or its float; E:18 means it tried to pump and the water never moved, so the fault is the pump or the drain line. Second, put your ear to the lower front during the drain phase. A pump that hums but moves no water is jammed or blocked; total silence when it should be pumping is a dead pump motor. Between the code and the hum test, you can name the cause before opening the cabinet.

The Causes, Most Common First#

Blocked drain pump impeller (about 35%)#

The leading cause is lint that slips past the filters and packs around the impeller into a felt-like plug, so the pump motor hums but the impeller cannot turn. Reach it through the lower front service panel — on most Bosch dryers it pops off on clips, no screws. Lay down towels, disconnect the pump, pull the impeller cover, and clear the lint from around the blades. Nine times out of ten this is a cleaning job, not a parts job.

Kinked or blocked drain hose (about 25%)#

On direct-drain installs a narrow hose — roughly 8 to 10 millimeters inside — carries water from the pump to a standpipe or drain. That small bore kinks easily when the dryer is shoved back against the wall, and over time it scales up with lint and mineral deposits. Disconnect it, flush it with water, and re-check the routing for a pinch; replace it if the inside is crusted with scale. This one often needs no part at all, just a re-route.

Stuck tank float sensor (about 20%)#

The tank's float tells the dryer when it is full. If scale deposits leave that float stuck in the raised position, the machine thinks the tank is always full and throws E:08 the instant you start a cycle — even with a bone-dry tank. Pull the tank, check that the float moves freely up and down, and clean any deposits with vinegar to free it. An E:08 with an empty tank is this fault until proven otherwise.

Drain pump motor failure (about 15%)#

A pump motor that has burned out from prolonged lint jamming or age gives no hum at all, and the water simply sits in the sump. Listen at the lower front during the drain step: dead silence when it should be running is the tell. Confirm with a meter — the pump windings should read roughly 50 to 200 ohms — and if the motor is open, the pump gets replaced rather than cleaned.

Clogged sump (about 5%)#

Least common, but stubborn: the sump beneath the condenser can build a plug of lint and soap residue that blocks water from ever reaching the pump intake. Clearing it means pulling the condenser for access, which is why it sits at the bottom of the list — check the easy causes first.

Work It in Order#

Put it together as a short sequence. Read the code: E:08 sends you to the tank and float, E:18 to the pump and drain. If the tank is genuinely full, empty it and restart — a cleared E:08 was just a full tank. An E:08 with an empty tank is a stuck float, so clean it. For E:18, check the pump for a hum, clean the impeller, and on a direct-drain setup flush the hose and check for kinks. Only after those come up empty do you pull the condenser to reach the sump. Cheap and common first, teardown last.

Keep the Water Moving#

Most drain faults trace back to lint that got past the filters, so the best prevention is upstream. Clean the lint filter after every load and rinse the fluff screen so fine lint never reaches the sump and pump in the first place. Rinse the condenser and its filter on the schedule your model calls for, since a clean condenser sheds less debris into the water path. On a direct-drain install, leave a little slack behind the machine and check the hose for a kink whenever you slide the dryer back against the wall. A few minutes of maintenance keeps the impeller clear and spares you the panel-off cleaning entirely.

Related reading: a Bosch dryer that's leaking water and [Bosch dryer error codes](/blog/bosch-dryer-error-codes).

Bosch [dryer repair](/bay-area/services/dryer-repair) across [Sacramento](/sacramento/sacramento) and the Bay Area — pump, hose, and float service in a single visit. Book your repair.