Introduction

In 1996 and 2002 the first general studies of the water supply of Ostia were published. The first is the work of Scrinari and Ricciardi: "La Civilta dell'Acqua in Ostia Antica", Roma 1996. The more recent one was written by Gemma Jansen. Jansen's PhD thesis was published in Dutch: "Water in de Romeinse stad (Water in the Roman city): Pompeii - Herculaneum - Ostia", Leuven 2002. On this page some highlights from her work are presented (the catalogues of Scrinari and Ricciardi are used throughout this website).

The raising of Ostia

For a study of Ostia's water supply the raising of the level of Ostia is a crucial background. In the east half of Ostia the following has been established (L. Sole):

1. A raising of c. 0.70 on top of the sand. On this layer rest the so-called Cippi of Caninius, that have been dated by Meiggs to c. 150-125 BC.
2. A raising of c. 0.80 on top of layer 1. On this layer rests the Republican Temple on the corner of Via dei Molini. This raising should probably be dated to the reign of Claudius.
3. A raising of c. 0.l5 on top of layer 2, probably from the reign of Domitian.
4. A raising of c. 0.25-0.75 on top of layer 3, probably from the reign of Hadrian.
5. A final, slight raising, probably Severan, taking the final level to c. 2.00-2.50 above the sand.

Jansen has established some remarkable facts about the raising of the late first and early second century AD. It was not a systematic attempt to increase the distance to the ground water or to the flood level of the Tiber. The raising did not lead to a flat surface, and not to a surface tilting to one side. There are great variations in the thickness of the raising. In any case, the raising necessitated a new system of water-supply and -drainage (lead and terracotta water pipes, sewers).

Ground water and rainwater

The ground water in Ostia is at a depth of only a few metres. The quality is good and the source reliable. Therefore it is not surprising that many wells were made in the city. They have a masonry shaft, and a well-head of masonry, terracotta or marble. Some could be closed off with a lid, and in a few cases holes have been preserved in which a lifting mechanism with a pulley was fastened. Terracotta pipes leading to the shaft prove, that sometimes rainwater was led to the wells. However, the collecting of rainwater was exceptional in Ostia. Most of it was led away unused. The ground water was even used in some baths, where it was taken to rooftanks by using waterwheels operated by slaves. In late anitquity, in a depopulated Ostia, wells were sometimes built on the middle of streets (Decumanus Maximus, Semita dei Cippi).

The aqueduct

The supply was greatly improved by the building of an aqueduct in the early Imperial period. The aqueduct is described on a separate page. The water of the aqueduct was taken to the buildings in various ways. The distribution could take place entirely underground, through lead pipes, sometimes having taps. Often the pipes carry stamps referring to the owners of the workshops where they were made (plumbarii) or to the owners of the buildings. A main pipe was found below the eastern stretch of the Decumanus Maximus, with the stamp colonorum coloniae ostiense ("of the colonists of the colony Ostia"). Sometimes the water was first led to a small distribution basin above ground, from where it was led to large tanks, such as the rooftanks in baths. The pressure of the water necessitated very thick walls supporting the tanks, sometimes with buttresses.

The water supply of street fountains and buildings

As we have seen the distribution reservoirs were filled with ground water and aqueduct water. From the reservoirs the water was led to 46 street fountains and 171 buildings (not counting baths!) in the excavated part of Ostia.

Street fountains could be simple basins, large covered basins and decorated nymphaea. The small basins are found typically near the entrance of baths and apartment buildings. A good example of a covered basin was found in Via della Fontana. Overflow holes in these basins prove that normally there was a continuous flow of water, with which buckets could be filled. However, water was also collected directly from the basins. This suggests that sometimes the flow of water was interrupted, albeit not for a long period of time, because the reserve in the basins was small. This in turn suggests, that the flow was regulated by people, because there was (just) not enough water available. The nymphaea are found along main streets and on squares. They adorned the city, but had a practical purpose as well: water could be collected from the overflow basins.

The types of connected buildings (excluding the baths) are listed below:

Type of building	Number of buildings	Total number of water outlets
Apartment buildings	21	37
Religious buildings	8	11
Guild seats	4	11
Houses	27	38
Commercial establishments	106	more than 150
Other	5	5
Total	171	more than 252

The number of water outlets per building is small. However, one outlet could have several functions. It could, for example, supply a nymphaeum, the overflow water of which was led to a toilet. As far as we know there were no outlets on the upper floors.

Toilets

The Ostian toilets consist of seats with holes (for obvious reasons) and with a hole in the front, through which a sponge on a stick could be used. The sponges could be cleaned in a bucket, a small basin, or in a gutter with running water in front of the seats. Urine and faeces were removed either by running water or manually, by using water in a bucket.

Toilets were found in 19 commercial establishments, usually below staircases. Toilets are normally present in the domus and medianum-apartments. Many communal toilets have also been found, either as separate units or incorporated in buildings such as baths and guild seats.

Sewers

The sewers can be traced and inspected through travertine and marble lids that cover vertical shafts leading to them. The sewers are rectangular tunnels covered by gable roofs (width 0.6-0.8 metres, height 0.6-1.4 metres). They received the waste water from baths, commercial buildings and houses, and from toilets, the overflow water from nymphaea and basins, and rainwater. Water was led from the roofs of buildings to the sewers through vertical terracotta pipes (usually embedded in grooves in the wall) and then through horizontal terracotta channels. The water that was used for cleaning the floors was led to the horizontal channels through small lids with holes in the floor. The only water on the streets was rainwater. Apparently this was not a problem, because sidewalks are low and there are no stepping stones in Ostia.

There are no great differences in height in the city (the maximum difference is 2.45 metres). Height measurements of the bottoms of the sewers have not yet been taken (the bottoms are covered with a thick layer of mud), but measurements of the streets have shown that the rainwater was not taken systematically to the Tiber or outside the city through the gates. It was taken to the sewers through lids with holes.