If your washing machine has a black jelly-like substance growing in the soap dispenser it is likely to be a fungal, bacterial growth called biofilm. Apart from looking nasty, it can block up the little holes in the top of many soap dispensers causing water flow to be restricted.
Partially blocked up nozzles can also cause water to get deflected into the fabric conditioner compartment causing the fabric conditioner to flush out too soon. Finally, deflected water can spray over to the front of the dispenser and leak out of the bottom of the dispenser drawer.
What causes the black jelly biofilm in the soap dispenser?
The growth is accelerated by moist environments. Bacteria and fungi need both water, and a source of nutrients. If both are present on a surface the organisms will grow and multiply to produce a grey/black jelly-like (slime) growth or produce a pink/red staining around bathroom tiles.
If you have a water valve not shutting off properly you can get a very small but constant drip of water into the soap dispenser. This can sometimes be observed by removing the soap drawer and seeing if you can see any dripping, or a bulging globule of water some time after the washing machine has finished. (If so, wipe the water away and see if it comes back, if it does you may need to have a new valve fitted although in some cases a badly blocked filter in the back of the valve can cause it not to shut off properly, or even water pressure that’s too low).
How to prevent biofilm growth
The best way to prevent this growth is to improve ventilation to allow these damp areas in kitchens and bathrooms to dry rapidly. With a washing machine I would leave the soap dispenser drawer open (at least partially) after using the machine drying it out manually first. If badly affected you may need to remove the drawer and wipe everything with kitchen towel or similar. It’s a pain, but large growths can be troublesome and may require a complete new soap dispenser to be fitted – plus the growth will reoccur if nothing is done to stop it or at least control it. Most soap dispenser drawers can easily be removed as there’s usually a clip to depress at the back which allows the drawer to come out.
It is also important to reduce the food sources for the bacteria and fungi to prevent growth. Food sources can include shampoo, soaps, propellants from hair spray and deodorants, and general kitchen food but with washing machines it’s clearly the detergent and fabric conditioner that the growth feeds on.
How to remove biofilm growth
Wiping with bleach or commercially available mildew removers should successfully remove the growth unless it’s really well established. Kitchen surfaces and bathroom tiles can be wiped with a household cleaner or mild bleach solution that will kill the bacteria and fungal spores.
Black slime associated with tap fittings can be removed by cleaning the inside of the tap or around the base of the tap with a small brush dipped in a mild solution of bleach. I used to have this problem with my bathroom taps. Little flakes of black substance would occasionally hang from the inside of the nozzle and if I pushed a bit of tissue up the nozzle to clean it there would be a slimy black jelly inside the tap.
Give your taps a very good clean occasionally by working a little disinfectant around not only the outside, but also the inside of the tap nozzle with a toothbrush or a cotton bud.
Removing the black growth from washing machine dispenser and drawer
If your washing machine’s soap dispenser is infested with a black growth try to clean it out with the soap drawer removed. Use on old toothbrush to clean the nozzles and top of the dispenser. Try using some of the products mentioned above. If it’s too bad to successfully remove it may need a new soap dispenser fitting
Further information – Slime and staining | Washing machine smells – causes of grease, slime and black mould inside washing machines (Washerhelp)