Where does Isle of Man tap water
come from?

impounding reservoirs page (read 18 October 2026) says Manx Utilities owns 7 impounding reservoirs, “4 of which are currently operational; West Baldwin, Sulby, Clypse and Kerrowdhoo.” Those four “provide raw water to the Island’s 2 water treatment works at Douglas and Sulby.” The same opening says Cringle and Ballure “are no longer used for drinking water supply” and that Block Eary “supplies water for hydroelectric power generation.”

Capacity is the stats-line figure, in the unit that line prints. A zone cell is that line’s wording. It is not a sample from a tap, and it is not a hardness result.

West Baldwin, Clypse and Kerrowdhoo are the Douglas side of that split. Clypse is the upper reservoir on the Groudle River, above Onchan. The page says that after Kerrowdhoo was completed, “the normal mode of operation of Clypse Reservoir became to feed water down into the new lower reservoir.” It then says the two reservoirs supply raw water to Douglas Water Treatment Works. Their shared stats line, and West Baldwin’s own line, name the same zone: Douglas, Onchan and the south of the Island. West Baldwin is also “sometimes known locally as Injebreck Reservoir.”

Sulby is the other route. The page calls it the largest and newest reservoir on the Island, completed in 1982. “Water from the reservoir is piped to Sulby Water Treatment Works where it is treated and distributed to the population in the north of the Island.” The same paragraph says Sulby water “can also be pumped to West Baldwin Reservoir, which supplies water to the Douglas area and the south of the Island via Douglas Water Treatment Works.” The stats line further down names places: “St Johns and Peel in the west, Kirk Michael, Ballaugh, Andreas, Bride and Ramsey in the north and Laxey, on the east coast.” Dalby is not in that list.

On Cringle, the page says it “formerly fed Ballagawne Water Treatment Works” before that works closed in early 2008. With Douglas works opening in 2008, Cringle “was decommissioned from being a public water supply reservoir later that year.” The page says the drinking water supply for the south “is now provided by water from West Baldwin, Clypse and Kerrowdhoo Reservoirs which is treated at Douglas Water Treatment Works,” and that Cringle “is now used solely for recreational purposes.” The Cringle paragraph does not mention the Sulby pump. Ballure “has not been used as a raw water resource since 2005 following the closure of the old treatment works” and “is now used solely for recreational purposes.” It “remains under the ownership of Manx Utilities.” Block Eary’s stats line says it is not currently a drinking water resource reservoir. The page says it is used principally for hydroelectric power generation, in conjunction with Sulby Reservoir.

What’s in our drinking water? (read 18 October 2026) says that on the Isle of Man raw water collects in reservoirs and stays naturally soft, because it passes over less porous rock. After treatment, it says, Manx drinking water remains soft at around 40 mg CaCO3/l total hardness (16 mg Ca/l). Which named areas have no hardness figure of their own is in Water hardness by area on the Isle of Man. The 2025/26 report’s area-of-supply sentence, which does name Dalby, and that report’s count of service reservoirs, are in the same article, from a reading on 13 October 2026. This note does not re-read the PDF, and it does not add Dalby to the Sulby stats line.

water treatment works page (read 18 October 2026) says there are 2 operational water treatment works, at Sulby and Douglas. It says a diagram of the basic water treatment process is shown below that sentence. The page does not print those steps as text, so this note does not supply them. It says a group tour of Douglas Water Treatment Works can be arranged. It does not print a telephone number or a form for that tour.

What does the Douglas works section say?

Douglas works “Opened in May 2008” and “provides treated water to Douglas, Onchan and the south of the Island.” West Baldwin, Clypse and Kerrowdhoo “supply raw water to the works.” It replaced Glencrutchery works, which “has since been demolished and the site is now owned by the Department of Education.” Glencrutchery was “Built in 1933,” “a single stage works, treating up to 18 megalitres of water daily for residents in the Douglas area.” The design sentence is printed without a full stop: “Douglas Water Treatment Works is designed to treat up to 37 megalitres of water a day, supplying 70% of the Island’s population”. The 37 megalitres and the 70% belong to that sentence, about Douglas works. The Sulby section does not give a design capacity.

What does the Sulby works section say?

Sulby works “Opened in October 2005”. The heading is “Sulby Water Treatment Works”. The sentence spells it “Sulby Water Treatment works” and says it “provides treated water to the north of the Island.” Sulby Reservoir “supplies raw water to the works.” This page does not print the town list from the reservoir stats line. An energy recovery system was installed in February 2013. Raw water “is piped from Sulby Reservoir to the treatment works and passes through a turbine” and then “passes through the treatment works and onto our customers.” “The turbine provides up to 50% of the electricity required to run Sulby Water Treatment Works.” That 50% is electricity for the works. It is not a share of the Island’s water, and it is not the separate hydro arrangement the reservoirs page describes at Block Eary.

What volumes does the about page give?

about-water page (read 18 October 2026) says that each year Manx Utilities collects, treats, stores and distributes over 10,000 megalitres of water, and takes over 3,600 water quality samples. In winter it supplies an average of 29 megalitres a day to over 50,000 connections, “through a network of over 1,800 km of mains, over an approximate area of 250 square miles.” Summer demand “rises to 35 megalitres per day.” The operational list on that page is 4 impounding reservoirs, 2 water treatment works, 20 pumping stations, 27 service reservoirs, and over 1,800 kilometres of water mains. The four reservoirs match the four the reservoirs page calls operational. The list does not name the 20 pumping stations, and this note does not open a pumping-stations page. The 37 megalitres at Douglas works and the 35 megalitre summer demand are left as separate sentences. This page does not subtract one from the other. The sample count printed in the 2025/26 report is left in the mains article. This note does not re-read that PDF.

service reservoirs page (read 18 October 2026) says “Treated water suitable for drinking is stored in service reservoirs.” It says not to confuse them with raw-water impounding reservoirs. They “need to be totally enclosed and protected from outside contamination by ground and surface water, animals, and vegetation.” The sizes it gives run from “small covered tanks storing only 22,730 litres” to “large concrete structures holding 22.7 megalitres.” It lists three jobs: a reserve against interruptions from pumping, treatment plant or mains failure; meeting fluctuating demand; and stable mains pressure to minimise burst mains. “We own 39 service reservoirs, 27 of which are currently operational.” The about page’s operational list also says 27 service reservoirs. Neither page names the 27 sites. The report’s count is the one already left in the hardness article.

Government Laboratory drinking-water page (read 18 October 2026) says the public water supply “is provided by Manx Utilities, to 7 defined supply areas,” and that laboratory staff sample consumers’ taps in each of those areas. The page does not name the seven areas, and it does not name these reservoirs. This note does not turn two treatment works into those seven names. The same page keeps a private well or borehole apart from the mains. That supply is the subject of Private wells and boreholes on the Isle of Man.

None of these pages names a kitchen filter, a cartridge or a reverse-osmosis unit on the route from reservoir to tap. The works page says the water is treated, then distributed. The service-reservoir page says treated water is stored, then the about page describes the mains. A filter at one sink would sit after that route, on the outlet it is connected to. No model has been selected for Manx Pure Water. This page makes no reduction claim and states no price.