For a leak from a Bosch WAT28400UC, Bosch's General Troubleshooting has two entries for water coming out from underneath the washer: the water supply hose is leaking because it is not screwed on tight at both ends, or the rubber washer is not placed in the hose (tighten the hose by hand at the washer end and check for a rubber washer), and the drain hose is leaking (check that it is on the washer securely with the clamp in place, and replace the drain hose if leaking continues). Foam that comes out of the dispenser is a separate issue from too much or non-HE detergent. Cleaning the drain pump cover must end with the cover screwed tightly into position with the handle vertical.
Differential
Likely causes of “Bosch 300 Series WAT28400 front-load washer is leaking water”, and how to tell them apart
- 1
A supply hose not tight or a missing rubber washer
What separates it There is water underneath at the hose ends because a supply hose is not tight or a rubber washer is missing
How to confirm Tighten by hand at the washer end and check the rubber washers
- 2
A drain hose not clamped securely
What separates it There is water under the washer while it drains because the drain hose is not clamped securely
How to confirm Check the clamp and replace the hose if it keeps leaking
- 3
A loose drain pump cover after cleaning
What separates it There is a drip at the service cover because the drain pump cover is loose after cleaning
How to confirm Screw the pump cover on tightly with the handle vertical
- 4
Foam from the dispenser
What separates it Suds and water appear at the front because of foam from the dispenser
How to confirm Use less detergent, and only HE detergent, then rerun
Before you touch a setting
Record this first — changing settings destroys the evidence
- Where the water appears and when
- Whether the pump cover was recently removed
- The detergent that you used lately
Try in this order
0 of 5 completedCheck the supply hoses
ReversibleCheck the supply hoses, which should be hand tight at both ends with the rubber washer in place.
Check the drain hose
ReversibleCheck the drain hose, which should be securely on the washer with the clamp in place.
Check the pump cover
ReversibleCheck the pump cover, and if it was removed, refit it tightly with the handle vertical.
Cut the suds
ReversibleCut the suds, by using less HE detergent, and do not use non HE detergent.
Run a short cycle
ReversibleRun a short cycle, and watch the connections while it fills and drains, and then test again to see whether it helped.
Model-specific
What is true of this model and not of its siblings
- Foam fix in Bosch's words
- If foam is coming out of the dispenser, an immediate fix is to mix 1 tablespoon of fabric softener with 1/2 liter (1 pint) of water and pour it into the detergent compartment, not with waterproof fabrics. To prevent it use less detergent for future loads and only HE detergent. The foam symbol at the end of a cycle means the washer added a rinse to remove foam.
- Strainers and leaks
- When you remove a supply hose to clean a strainer, water under pressure can leak, so Bosch describes de-pressurizing first: turn off the tap, turn the selector to a wash cycle, touch Start/Pause and wait 30 seconds, then turn the selector to Off. After cleaning, check that the rubber washers are seated at both ends of the hose and the connections are properly tightened.
- Parts for this problem on the WAT28400 (RepairClinic, 2026-09-20)
- door boot seal, part number 20007273, at $90.56; hose clamp, part number 00621484, at $1.91; drain pump, part number 00145753, at $155.35; water inlet valve, part number 00635399, at $146.39.
- Other models this page answers
- These steps also fit the 300 Series WGA12400UC washer, 800 Series WAW285H2UC washer, 800 Series WGB24600UC washer.
Stop boundary
When this stops being a self-service repair
- !If water comes from inside the cabinet, call Bosch customer service
- !If the drain hose keeps leaking after the clamp is checked, replace it
Evidence ledger
Sources behind this answer
Bosch's own US owner-support pages for washer error codes and self-help.
Parts and list prices as shown on RepairClinic's parts search for this model number on 2026-09-20.
Exact questions
Common questions
Where do Bosch leaks usually come from?+
The supply hoses, the drain hose or the pump cover.
Should I overtighten the hoses?+
Hand tighten only, with the rubber washers seated.
What if the drain hose keeps leaking?+
Replace it; Bosch says it may need replacing if leaking continues.
Can foam cause a leak?+
Foam from the dispenser can run onto the floor; use less detergent.
Can I reuse an old drain hose?+
No; Bosch says to use only the drain hose specified.