This is an instructable on how I renewed the grout in my shower. This is a picture of the grout before being renewed.

The problem:
Over time, grout may become discolored due to mold or mildew build-up as shown in the picture (the grout on the walls should be white, but it actually looks more like brown).

The solution:
I attempted to solve this problem as efficiently as I could by discovering alternative uses for existing materials/supplies.

Required materials and supplies:
> Hard bristle toothbrush
> Container
> Bleach
> Rubber gloves
> Narrow tip paintbrush
> Grout sealer

Step 1: Cleaning the Grout

1) Find an old hard bristle tooth and a container to hold liquid (I used an old tofu container).

2) Put on rubber gloves and ventilate your work area (open a window, etc.) because the following steps involve bleach which can be an irritant and give off a strong smell. Follow the bleach manufacturer’s safety instructions.

3) Pour a small amount of bleach and water into the container (I prefer a water to bleach ratio of 2:1). We will use this to clean the grout.

4) Dip the toothbrush into your mixture and lightly scrub back and forth onto your grout to clean it.

5) After you finish cleaning, wait for the grout to dry.

Step 2: Sealing the Grout

1) Sealing your grout will help to prevent it from becoming discolored due to mold or mildew build-up in the future. Note that you should re-seal your grout once in a while depending on what the manufacturer recommends.

2) Follow the instructions provided with your grout sealer to seal your grout. Basically, you use your paintbrush to apply a very thin coat of sealer onto your grout. Try to avoid getting the sealer on unintended areas. Some sealers require two coats; I recommend you use sealers that only require one coat to reduce the amount of work.