For a Bosch WAT28400UC that does not get laundry clean, Bosch's manual points to the detergent and the load. It is a high-efficiency washer that needs HE detergent, dosed correctly (see Adding the correct amount of HE detergent); a small drum load of 15.4 lb (7 kg) for regular cotton is the maximum; some phosphate-free detergents leave light spots that are brushed off when dry or removed with the Rinse program. Dry detergent that was damp or lumpy, excess liquid detergent or a blocked supply can leave detergent unwashed. SpeedPerfect gives a shorter wash comparable to the standard program, and Prewash and the soaking option handle heavy soil.
Differential
Likely causes of “Bosch 300 Series WAT28400 front-load washer does not clean clothes well”, and how to tell them apart
- 1
Wrong detergent or dose
What separates it There is poor cleaning and there is residue because of the wrong detergent or the wrong dose
How to confirm Use only HE detergent in the right amount; use the dosing cup for liquid detergent
- 2
An overloaded drum
What separates it The clothes are packed and dirty because the drum is overloaded
How to confirm Stay within the 15.4 lb (7 kg) capacity for regular cotton
- 3
Water supply problems
What separates it The detergent is not washed away because of water supply problems
How to confirm Check taps, hoses and strainers and the water pressure
- 4
Phosphate-free detergent residue
What separates it There are light spots on dark laundry because of phosphate free detergent residue
How to confirm Brush off when dry or run the Rinse program
Before you touch a setting
Record this first — changing settings destroys the evidence
- What the laundry looks like after the wash
- The detergent type and the dose that you used
- The cycle, temperature and load size
Try in this order
0 of 5 completedUse the right cycle
ReversibleChoose the cycle for the fabric and set the temperature; see the program selection table.
Dose HE detergent
ReversibleDose HE detergent, by using the recommended amount and the dosing cup for liquid detergent.
Do not overload
ReversibleDo not overload, and keep regular cotton loads up to 15.4 lb, or 7 kg.
Use Prewash or soak
ReversibleUse Prewash or soak, and for heavily soiled loads, add Prewash or the soaking option.
Check the supply
ReversibleCheck the supply, with the taps on, the hoses free and the strainers clean, and then test again to see whether it helped.
Model-specific
What is true of this model and not of its siblings
- Loading the washer
- Bosch says to load laundry of the same color for the soaking option and that no additional detergent is required because the soaking solution is used for washing. The drum's regular cotton capacity is 15.4 lb (7 kg), and small and large items should be mixed so the washer can balance the load. Overloading leaves detergent unrinsed and laundry poorly cleaned.
- Before the first load
- A Bosch washer is tested at the factory, so a small amount of residual water may remain in the drum. Bosch recommends running the Drum Clean program with no laundry, after adding 1 to 2 tablespoons of detergent to the main-wash chamber II, before the first load. It cleans the system and is also the maintenance program for later use.
- Parts for this problem on the WAT28400 (RepairClinic, 2026-09-20)
- water inlet valve, part number 00635399, at $146.39; dispenser, part number 11051387, at $177.22; motor, part number 00145752, at $100.78.
- 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 washing results stay poor with the right detergent, load and cycle, call Bosch customer service
- !If the washer does not fill or drain, follow those pages first
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
Why is my Bosch laundry not clean?+
Detergent type or dose, an overloaded drum, or a water supply problem.
What is the maximum load?+
15.4 lb (7 kg) for regular cotton loads.
What does Prewash do?+
It adds a prewash stage for heavily soiled laundry.
Are light spots detergent residue?+
Some phosphate-free detergents contain insoluble ingredients that may look like light spots.
Do I need extra detergent for the soak?+
No; the soaking solution is used for washing.