Wash the rhubarb thoroughly and chop it into small pieces.

In a large pot, combine the chopped rhubarb and water.

Bring the mixture to a boil over medium heat.

Once boiling, reduce the heat and let it simmer for about 30 minutes.

After simmering, remove the pot from heat and strain the mixture through a strainer or cheesecloth into another container.

Add sugar to the strained juice while it's still warm, stirring until dissolved.

If desired, mix in lemon juice to enhance the flavor.

Let the juice cool before transferring it to a bottle or jar.