On the Geometry of the Minoan Water Conduits

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IWA Specialized Conference on Water&Wastewater 22-24 March 2012
Technologies in Ancient Civilizations Istanbul-Turkey
172
MN-032
On the Geometry of the Minoan Water Conduits
An. Angelakisa, D. Koutsoyiannisb and P. Papanicolaoub
aNational Agricultural Research Foundation (N.AG.RE.F.), Institute of Iraklion, 71307
Iraklion, and Hellenic Water Supply and Sewerage Systems Association, 41222
Larissa,Hellas
(E-mail :info@a-angelakis.gr)
bDepartment of Water Resources, Faculty of Civil Engineering, National Technical University
of Athens, Heroon Polytechneiou 5, GR 157 80 Zographou, Hellas.
Abstract Several different types of conduits were found in archaeological excavations in
Crete belonging to the Minoan period. They were used for water supply as well as for
stormwater and wastewater removal and are made of stone or terracotta. The terracotta
conduits were canals or pipes with rectangular or circular cross section. The most interesting
conduits are the terracotta pipes of truncated conic shape which were never used before or
later in other civilizations. An ongoing experiment using reconstructed pipes of this shape will
be employed to evaluate their hydraulic behaviour and investigate possible advantages for
certain flow conditions.
Keywords: Bronze Age; Knossos; Myrtos Pyrgos; open conduits; Phaistos; Stone conduits;
terracota pipes; Tylissos; Zakros
INTRODUCTION
The island of Crete in Greece, was first inhabited shortly after ca. 6000 BC but only during
the Bronze Age that the Minoan civilization was developed as the primary Greek cultural
centre of the Aegean world (Alexiou, 1964). The Minoan and Mycenaean settlements (in
Crete and Peloponnesus, respectively) developed and applied various technologies for
collecting, storing, transporting and using surface-water and ground-water resources
(Angelakis and Spyridakis, 2010; Koutsoyiannis et al., 2008).
Over the past century archaeological excavations have brought to light impressive water
engineering technology dating from the Minoan era on the island of Crete (Angelakis and
Spyridakis, 1996; Webster and Hughes, 2010; Angelakis and Spyridakis, 2010;
Koutsoyiannis et al., 2008; Antoniou and Angelakis, 2011, and others). From the early Minoan
period (ca. 3200-2300 BC) issues related to water supply were considered of great
importance and developed accordingly. Archaeological and other evidence indicate that
during the Bronze Age advanced water management and sanitary techniques were
practiced. Several types of stone and terracotta conduits and pipes were used to transfer
water, and drain stormwater and wastewater. These types of conduits are summarized
below.
STONE CONDUITS
In Crete due to dry summers rainfall harvesting was necessary and was accomplished from
both roofs of the buildings and larger court areas. Hydraulic structures associated with the
rainfall collection were found in Knossos, Phaistos, Tylissos, Aghia Triadha, Chamaizi,
Myrtos Pyrgos and Zakros. These include stone-made conduits with branches that were
used to supply collected water to cisterns. The Knossos palace provides a typical example
(Figure 1, left). Also, alongside a stairway in Knossos is a small stepped channel consisting

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of a series of parabolic-shaped step chutes that was used to convey rainwater from terraces
down to a sedimentation basin (Figure 1, right). In Tylissos houses, similar stone conduits
Figure 1. Minoan rainwater collection systems in the Knossos palace: carved stone elements
of a conduit for the flow of rainwater falling on the roof (left) and part of restored stairway with
parabolic runnels for rainwater flow (right); photos by A. Angelakis.
Figure 2. Minoan stone conduit systems (part of aqueduct) at Tylissos: to transfer the water
from a sedimentation tank to the main storage cistern (left) and part of distribution network
(right); photos by A. Angelakis.
were used to convey water from a stone made sedimentation tank to the main storage
cistern (Figure 2, left). The same components of rainfall harvesting system, e.g. cistern,
channel and sedimentation tank, also existed in other settlements (Angelakis and Spyridakis,
1996; Gorokhovich et al., 2011). Furthermore, in several palaces parts of the sewer systems
were made of stone conduits (Figure 2).
TERRACOTA CONDUITS WITH OPEN-SHAPED CROSS SECTIONS
While conduits of large cross section were stone made, those with smaller cross section
were made from terracotta in the form of U-shaped tiles. Such terracotta conduits were
discovered as parts of sewer networks at the Knossos and Phaistos palaces and other
Minoan settlements (Figure 3; see also Angelakis and Spyridakis, 1996; Angelakis and
Koutsoyiannis, 2003; Antoniou and Angelakis, 2011). It is noted that U-shaped terracotta

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drains covered with stone slabs, running below the streets, were also found in Habuba
Kabira, a small Sumerian city of the Bronze Age (Viollet, 2002).
Figure 3. U-shaped terracotta drains at Phaistos palace (top left) and the Knossos palace
(bottom left and right); photo by M.Nikiforakis, EFIAP, with permission.
TERRACOTTA PIPES
The most interesting Minoan conduits were the pipes made of terracotta. As shown in Figure
4, two types of such pipes were found, the prismatic and the truncated conic ones. The
former, found in Myrtos – Pyrgos and used to supply the nearby cistern system with
stormwater collected from the rooftops and open courtyards (Cadogan, 1978), probably
operated under free-surface (open channel) conditions. Rectangular openings and covers of
same material were used to interconnect of consecutive segments. These pipes were used
for water supply and could operate at full-flow condition, perhaps under low pressure. Neither
type of terracotta conduits is known to be used before by other Bronze Age civilizations or
subsequent civilizations in the Mediterranean region. In particular, pipes with circular cross
section were widespread in later phases of the Greek civilization (Angelakis et al, 2005;
Koutsoyiannis et al., 2008) but they were cylindrical rather than conic and operated under
free surface conditions.

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Technologies in Ancient Civilizations Istanbul-Turkey
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Figure 4. Minoan terracotta pipes used for collecting and storage of rainwater of rectangular
shape from Myrtos- Pyrgos (upper) and remains of water supply system at Knossos palace
(lower); photos by A. Angelakis with permission.
The hypothesis that these pipes may have been used in low pressure conditions is supported
by other archaeological findings indicating that pressurized flow was known. Specifically, a
fresco found in the Knossos palace (Fahlbusch, 2008; Koutsoyiannis et al., 2008), depicts a
jet d’eau (fountain) which would not be possible without pressurized flow.
The pipes at Knossos were made 76 to 82 cm long with a thickness of 1-2 cm (Figures 4 and
5). The smaller end had a diameter of 7.5-8.3 cm and the larger 15-17 cm (Angelakis et al.,
2007). The particular shape of these pipes facilitated tight interlocking (using plaster) of
consecutive sections. Clearly the taper in each section was significant; the diameter doubled
over the full length of each pipe section (Figure 5, lower). The reason behind this strongly
conical pipe design is still uncertain and provides somewhat of a puzzle (Webster and
Hughes, 2010).
The tapered Minoan pipes do not reappear in the water technology of later civilizations in the
Mediterranean region, either because the technology was abandoned for being
unsatisfactory, or because it was simply lost. Transfer of knowledge from the Minoan
civilization to the later Greek civilization is debated in the literature. Some believe that water
engineering skills were lost following the collapse of Minoan culture and rediscovered after

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800 BC (Webster and Hughes, 2010). Any reasoning behind the tapered pipe design may well
have been forgotten, with water pipes reappearing with a different design.
Conical pipes are entirely unique to Minoan Crete, which have been used predominantly in
the context of water supply. There is some reason to expect that the Minoans had a good
reason to support their conical geometry. Based on Minoan water engineering skill as
demonstrated in other infrastructure (e.g. drainage and sewage), it seems reasonable to
expect that the Minoans were very deliberate in their choice of pipe design. The quality of
pipe manufacture, featuring tightly fitting joints and cement-seals, also suggests that the pipe
design was selected with care.
Minoan pipes were recently reconstructed following same technique, using the same
material, and in same geometry are shown in Figure 5. An ongoing experiment using
reconstructed pipes of this shape will be utilized to analyze their hydraulic behaviour and
investigate if they have advantages over the ones with cylindrical shape. Possible
advantages to be investigated are:
a) At the manufacturing phase, the conical shape was perhaps easier to construct than a
cylindrical one
b) At the construction phase, the conical shape may have served better the joint design
and application.
c) Also, at the construction phase, curved alignments were perhaps implemented easier
by the conic shape.
d) In terms of hydraulic function, the conic shape clearly results in greater head losses
(additional losses at the places where sudden changes in diameter occur; Webster and
Hughes, 2010); however, in steep terrains this may be an advantage in either partial or
full flow conditions.
e) In terms of their function with respect to sedimentation, the conical pipes may have
better properties in avoiding formation of deposits due to increasing velocity.
0.085
0.72
0.065
0.17
0.025
Figure 5. Knossos water supply pipes: Terracotta pipe dimensions (top) and recently
constructed pipes of same material and geometry (bottom); photo by M.Nikiforakis, EFIAP
with permission.

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SUMMARY AND CONCLUSIONS
In Minoan Crete (Knossos, Tylissos, Malia, and other sites) aqueducts have been used to
convey potable water from mountain springs to Minoan palaces and towns, as well as
sewerage and drainage systems to collect rain water from the roofs and bring it to storage or
remove the wastewater. Aqueducts and sewerage and drainage systems consisted of open
channels, closed conduits or combinations thereof. The open channels were typically
rectangular made of stone, or U-shaped made of stones or terracotta. Among the terracotta
pipes, most interesting were those with truncated conic shape, manufactured in sections 70-
75 cm long. The design of these pipes differs notably from later Greek cylindrical, almost
constant diameter pipes, for having tapered conic section in the direction of flow. One
potential advantage of such design is the perfect seal of the joints with clay or other material,
so that they possibly can operate under low pressure. Another advantage is the flexibility for
change in direction without use of special elbow fittings, while it has been additionally
speculated in the literature that the velocity increase associated with the narrow end of each
pipe section, helped to flush sediment through the pipe and prevent deposits. These possible
advantages will be assessed through an experiment with terracotta pipes reconstructed
recently resembling the original Minoan pipes.
ACKNOWLEDGEMENTS
This work was partially supported by the EU-research project INCO 517612 (MELIA). Also,
the pipes in Figure 5 were replicated in the Contemporary Ceramics Workshop, by Mr. D.
Lyberides, Kokini Chani, 71500 Iraklion, Greece.
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