Here are two of my favorite methods for removing tough limescale from shower heads and hoses.
This first method is used for when you can remove the shower head and hose from its casing. If you are unsure how to do this try looking it up on YouTube. They are all different.
You will need
2 litres of white vinegar
A squeeze of a few lemons, or 2 tablespoons of citric acid
A large enough bucket to cover the shower head
Hot, but not boiling water, around 90 degrees
Step 1 - Remove shower head and hose and place in bucket.
Step 2 - Cover with white vinegar and fill with hot water. Add a squeeze of a few lemons or add the citric acid.
Step 3 - Leave for around half an hour for the acid to eat away at the limescale. After this remove the shower head and scrub the tough stains with a toothbrush. Repeat the same with the hose.
Step 4 - If any limescale remains repeat step 3. Leave overnight if possible.
Step 5 - Once all limescale has been dissolved its time to rinse well, using warm tap water. Dry and buff if needed.
Step 6 - Replace shower head and hose.
This method is intended for when the shower head cannot be removed.
Step 1 - Remove as much limescale as possible using citric acid and a toothbrush.
Step 2 - Fill a black bin liner, or strong carrier bag with white vinegar and a few tablespoons of citric acid.
Step 3 - Tie the bag over the shower head so it is soaking in the solution. Tie using hairbands or elastic bands and leave for around an hour.
Step 4 - Remove the bag and scrub away any remaining limescale. Repeat this step if necessary.
Step 5 - Rince off the vinegar using a wet cloth and buff dry.