Edinburgh Water Company and its successors have provided a public water supply and latterly sewerage and sewage treatment services to the Scottish capital of Edinburgh since 1819. The original company was established to supply drinking water and did so until 1870, when it was taken over by a public water trust, with representatives from Edinburgh, Leith and Portobello. The company built an associated railway, the Talla Railway and a rural manor house, with an associated station Victoria Lodge railway station. The trust was taken over by Edinburgh Corporation and in 1975, responsibility passed to the Lothian Regional Council, as did the duty to provide sewerage and sewage treatment services. Both services were moved out of local authority control, and taken over by the East of Scotland Water Authority in 1996. The three Scottish regional water authorities were merged to form Scottish Water in 2002.

During the time of the Edinburgh Water Company and the Edinburgh Water Trust, major projects were carried out to construct reservoirs, some for the impounding of water supplies, and others to provide compensation water, to ensure that rivers could still provide water power to mills, when some of their sources had been tapped to supply Edinburgh. James Jardine was the company's first engineer, and was succeeded by James Leslie, who became part of J & A Leslie and Reid, when he entered into partnership with his son Alexander Leslie and son-in-law Robert Reid in the early 1870s. The last major project of this early period was Talla Reservoir, completed in 1905, but there were further civil engineering projects in the 1960s and 1980s. Alexander Leslie compiled a dosier of photographs, showing the construction of some of the later Victorian reservoirs, which has recently been rediscovered in the archives of Edinburgh Library.

With the population growing rapidly, a major project to divert sewage away from the Water of Leith, the main river through the city, took place in 1864, probably with Napier Bell as the engineer. A new sewer intercepted the existing sewers and drains, and carried the raw sewage to the sea. Edinburgh did not have a sewage treatment works until 1978, when construction of Seafield Treatment Works on reclaimed land near Leith Docks was completed. It now produces 2.3 MW of electric power, generated from the gas which is a product of the sludge digesters which treat the effluent, and it is expected to become self-sufficient for power in the near future.

The City of Edinburgh had a number of wells, from which water could be obtained, and Nor Loch also acted as a source for water. Water was first brought in from outside the city in 1676, when a 3-inch (7.6 cm) lead pipe was installed from springs at Comiston, now a suburb to the south of the city. As more water was required, additional springs in Comiston were tapped, and the pipe was progressively replaced by a 5-inch (13 cm) lead pipe between 1704 and 1720. Iron pipework replaced the lead in 1820. The network was extended in 1760, when wooden pipes were laid into the city from springs near Swanston, a little further to the south, but now also a suburb. 7-inch (18 cm) iron pipes replaced the wooden pipes around 1790, but there was then a lull in development due to the Napoleonic Wars. The piped water reached a fairly limited number of dwellings, and many people had to buy water from water porters, called 'caddies' locally, who were registered by the magistrates, and sold water for one penny for a barrel containing 5 to 6 imperial gallons (23 to 27 L).

There was general disquiet that the supply of water was "extremely deficient both in quantity and quality," and the editor of the Edinburgh Review, Francis Jeffrey, convened a public meeting, at which a committee was formed to take the matter forwards. The committee included two prominent authors, Henry Mackenzie and Henry Cockburn. The Edinburgh Water Company was formed, and obtained an act of Parliament, the Edinburgh Water Company's Act 1819 (59 Geo. 3. c. cxvi) in July 1819. This authorised several schemes, including obtaining water from the Crawley springs, some 6 miles (9.7 km) to the south of Edinburgh in the Pentland Hills, an idea that had first been suggested by Thomas Telford in 1811. They could also take water from the Glencorse Burn, and in order to maintain supplies to mill owners on the River Esk, the Glencorse Reservoir was to be built, as a source of compensation water.

James Jardine was appointed as the company's first engineer, who had been involved in the construction of the Union Canal, and who had also been the first person to work out the mean level of the sea. He was responsible for the pipeline from Crawley springs, which was 8.5 miles (13.7 km) long, as it followed the contours, and acted as resident engineer for the Glencorse dam, with Telford acting as the chief designer. The water pipeline, which varied in diameter from 15 to 20 inches (38 to 51 cm), was completed in August 1823, and delivered 1,500,000 imperial gallons (6.8 Ml) per day to the city. The Glencorse dam, which impounded 368 million imperial gallons (1,670 Ml) of water, was one of the tallest earth dams at the time it was built, with the crest around 120 feet (37 m) above ground level. The total cost of these projects was around £145,000, and they received high praise from The Scotsman newspaper. Jardine had originally calculated water levels and potential yields from the springs in the Pentland Hills in 1810, while working for Telford.

The new scheme worked well until 1842, when there was a severe drought, resulting in many of the smaller streams and brooks drying up completely. Less than 12 inches (300 mm) of rain fell between April and October, and the Glencorse Reservoir emptied. Millers on the River Esk demanded that water from the Crawley springs should be diverted into the Glencorse Burn, and this was only avoided by paying them an indemnity of between £4,000 and £5,000. The company rushed through the Edinburgh Water Company's Act 1843 (6 & 7 Vict. c. lxxxix) to allow them to abstract water from streams at Listonshiels, Bavelaw and Black Springs, all of which are on the north side of the Pentland Hills. Two more reservoirs were required to provide compensation water, at Threipmuir and Harlaw, and despite difficulties in buying the required land, Jardine pressed on with the project. However, he retired in 1846 before either reservoir had been finished, having reached the age of 70, and it was James Leslie who took over and saw them completed.

Leslie had previously worked with Jardine on a report about a water supply scheme for Dundee, for which an act of Parliament, the Dundee Water Act 1837 (7 Will. 4 & 1 Vict. c cxxvi), was obtained, but no work was undertaken at the time. Construction of the dam for the Threipmuir Reservoir may have been completed before Jardine retired, but the Harlaw dam was definitely Leslie's work. The main outlet for the reservoir was through a cast iron pipe sitting on the foundations for the dam. A masonry tower was built at the inner end of the pipeline, near the upstream toe of the dam, and a rod passing up the tower enabled the sluice to be controlled. To enable the outlet valve to be inspected or maintained, a sluice made of oak could be lowered in guides, cutting off the incoming water and allowing the pipeline to drain. A second similar structure allowed water to be taken from about 40 feet (12 m) above the bottom of the reservoir. When the dam was nearly completed, there was evidence of slippage on the upstream face, which displaced the tower slightly. Leslie put this down to the dam being built too quickly, with insufficient attention being paid to consolidating the hard boulder clay from which much of the dam was constructed, and all his subsequent dams were constructed in layers less than 1 foot (300 mm) thick, to mitigate such problems. Despite the movement of the tower, no remedial work was undertaken, and it has remained standing ever since. Leslie completed the work specified by the Edinburgh Water Company Act 1843 in 1848.