The Water Tower is believed to have been added to the curtain wall in the early 14th century.   Inexplicably it has 4 scuppers, or drain spouts, to clear water from the roofs, even though just one would suffice for such a relatively small roof area.   Scuppers, often sculpted into fantastical creatures called gargoyles, would typically be required for every 20 feet of parapet walling, yet only a couple remain anywhere else throughout the castle ruins.

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         Water in the culvert from the mere powered the mill and then discharged underneath the Water Tower, and thereby also serviced its latrines.   It cannot be confirmed whether this culvert might also have received discharge from the stables, because this important feature, previously visible under a covering grate outside the Water Tower, is currently completely obscured.

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         The historian John Britton, writing in 1814, claimed that ‘from this tower, buildings in the upper ward of the castle were supplied with water, by means of an engine’, but provided no clarification or evidence.   By this date it had been in use as a dovecote for over 60 years.

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         In the ground floor chamber of the Water Tower, an irregular vertical channel is cut into the inside of the wall to the inner court, extending up to the fireplace on the first floor.   It may have been used to dispose of fire ash, down into the culvert running below the ground floor.

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         The latrine in the ground floor was found to contain the remains of a ‘Moule’s earth closet’, patented in 1860, a rival to water closets in the 19th century, and still in use in the 20th century in rural areas.   The first water flushing toilet had been described in 1596 by Sir John Harington, a godson of Queen Elizabeth, for whom he installed a working model at Richmond Palace.

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         A spiral staircase, featuring a rare stone handrail, led to a ‘Queen’s Chamber’ on the first floor, and then to a likely guard chamber above.