Low-temperature washing can cause liquid fabric softener and detergent to remain undissolved in washing machine outlet pipes. Eventually they will form a slimy substance, which may block drains, either partially or completely. Strong drain cleaner cannot be used in a washing machine and is not recommended for plastic pipes. Natural cleaners can solve the problem and are environmentally-friendly at the same time.
Clear the blockage with seltzer tablets. If you have access to the pipe, drop three seltzer tablets down, followed by a cup of vinegar. Give the solution a few minutes to work, then pour down very hot water. If you are unable to access the pipe, proceed to Step 2.
Pour ½-cup of baking soda and ½-cup of vinegar into washing machine drum. Run the machine on its hottest setting. The resulting fizzy chemical reaction should clear the pipes of undissolved fabric conditioner and powder. If the blockage remains, repeat the procedure or try a borax solution as follows.
Mix two cups of borax with two cups of very hot water. Pour carefully down drain. This solution can also be run through the machine on the hottest setting.
Run the machine empty on the hottest cycle at least once a month. Put ½ cup baking soda in the dispenser. This will kill bacteria in the machine and drains. Use half as much powder and fabric conditioner as the manufacturer recommends. Laundry will wash perfectly clean and fresh with less, and drains will remain unblocked. If there are suds left in the laundry after the wash cycle, run them through a rinse cycle with ½-cup vinegar. To revive over-conditioned towels, wash them on the hottest setting with ½-cup of vinegar in the dispenser. Towels will be softer and more absorbent and you will be helping to keep the drain clear at the same time. Consider using an environmentally-friendly washing powder. It is less likely to clog up drains.
Don't pour boiling water down plastic pipes as they could melt or distort. Take care when handling borax; it is slightly toxic and is a skin irritant. Wear protective gloves and keep borax away from children and pets.