Washing Machine Soap Drawer Cleaning
The soap drawer in a washing machine is more prone to limescale issues than anything else in most machines. Not so much the drawer that you place detergent and conditioner in, but the jets that allow the water in above that are prone to blockage from limescale and general bacteria build up.
The actual soap drawer will almost always have some method of releasing from the washing machine, some pull straight out while others have a release tab that need to be pressed. Once out, take the syphon found at the back of the conditioner compartment off and clean the whole drawer very thoroughly with a stiff brush in warm water. A brush for washing dishes with is ideal for this process and the next step.
Do not put the soap drawer in a dishwasher as the heat may warp it.
Washing Machine Soap Dispenser Compartment Cleaning
The soap dispenser compartment also requires cleaning. A good bleach diluted in some warm water is ideal for this part of the process along with the brush mentioned previously. Thoroughly clean the compartment with the brush, paying particular attention to the corners as this is where bacteria will lurk.
Where limescale will be an issue is on the dispenser jets that you will see by looking at the top of the empty compartment. These jets are commonly blocked by limescale and bacteria deposits and, if not regularly cleaned, the assembly may have to be replaced in the worst instances which will usually require the services of an engineer. With your brush give the jets a good clean and try to get the bristles of the brush into the small holes (the jets) to ensure that they are clear of any blockage. After cleaning the soap drawer can be reinserted.
Limescale Inside The Washing Machine
Some washing machines have a small "bell" on the pressure chamber leading to the pressure switch hose. This "bell" can become blocked with limescale and cause problems. This is, apart from a bit of limescale on the element, usually about the worst we see in terms of limescale build up.
However, running a lot of low temperature washes and, especially so if you only (or mostly use liquid detergent or a detergent for colour only. Neither contain bleach and low temperature washes are not sufficient to activate a lot of components within the detergents, of any type, to combat limescale.
In any boxed powder there are elements known as "builders" that will capture and remove limescale. Dosed correctly there should be no need for any limescale removal products at all.
Running correctly dosed maintenance washes once every month or so should be all that is necessary to prevent limescale building up to a point that it causes trouble with the machine.
Where Limescale Has Already Caused A Problem
If limescale has been allowed to build up to a point where it is starting to be a real problem, there are a few ways it can be treated. The calicum carbonate can be easily dissolved in mild acids, you can buy commercial limescale removers for the job but a range of household substances are good for the job too. Two of the most effective substances are lemon juice and ordinary vinegar. Lemon juice is usually the best (and will also leave a lovely smell behind). Stronger pickling vinegar and lime juice are both even more acidic and can be used for really stubborn deposits.
The problem with removing limescale is not usually finding an appropriate acid around the home, but making sure the acid stays in contact with the surface for long enough to do its job. Limescale is not so easy to remove that you can simply wipe it off with a cloth soaked in juice. Instead, you need to leave it soaking for an hour or more to really do the trick.
Use a large cup of either liquid in place of your usual detergent and run a normal washing cycle (without clothes).