Wash the oranges and lemons thoroughly.

Using a sharp knife or vegetable peeler, remove zest from four oranges. Be careful to avoid getting too much of the white pith, as it can make the marmalade bitter.

If using varieties with seeds, make sure to remove them, as they can make your orange jam taste bitter.

Carefully mix chopped oranges, lemons and the reserved zest with sugar in a large pot. Let it sit for about 1-2 hours. Then, add all the measured out water to the pot with the fruit and sugar.

Place the pot on the stove over medium heat. Bring the mixture to a gentle boil, stirring occasionally to ensure the sugar is completely dissolved.

Once the mixture reaches a boil, reduce the heat to low and let it simmer uncovered for about 2 hours. Stir occasionally to prevent sticking and burning.

After about 2 hours, the chopped fruit and zest should be soft enough for further processing.

Set up a metal mesh kitchen strainer over a large bowl to catch the pulp and juices. Using a ladle or large metal spoon, remove the cooked zest and fruit into the strainer.

Press and rub the cooked fruit against the mesh, pushing the pulp and juices through. Discard the solids remaining in the strainer and pour the strained jam back into the pot.

Add the pectin to the pot and thoroughly mix it with the jam using a whisk.

Bring the jam in the pot to a gentle boil over medium-low heat and let it boil for 30 minutes to one hour, depending on the desired consistency. Stir regularly to prevent sticking.

Perform a chilled plate test to ensure you are happy with the jam's consistency.

Once satisfied, process the jam using your preferred canning method.