Manx Utilities says the old Castletown Road will close for more than two weeks next month.
It says the White Hoe Wastewater Pumping Station needs essential refurbishment work, including replacing manhole covers.
As a result, the road will close from Monday, March 9 until Wednesday, March 25.
Motorists will be diverted to the White Hoe Industrial Estate via Kewaigue Hill Road, and via Quarterbridge into Douglas.
Road closures planned for tin baths this weekend
DOI has no junction safety concerns over Iceland plans
LegCo to face questions in this morning's sitting
Passport prices to rise
House of Keys to sit for final time before election
Island cyclist to ride in Tour De France
Police appeal over promenade street brawl
Well-known farm in the west up for sale