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Acta Polytechnica Vol. 51 No. 5/2011

Prague’s Water Supply Station in Podoĺı — a Solution for the
Problems of Clean Water in the 1930s

K. Drnek

Abstract

In the 1920s Prague was seeking a solution to the problem of supplying its inhabitants with drinkable water. The water
plant in Káraný was not able to provide enough water, and the bold plan to bring water from a reservoir and to provide
a dual system of potable and non-potable water faced an uncertain future.
In order to stave off the crisis and make time to complete its plans, the city council decided to construct a new water

supply plant inside the city next to the Vltava river in the city district of Podoĺı.

Keywords: Káraný, Ing. Jaroslav Vancl, Podoĺı, Puech-Chabal, filtration, large mesh filters, prefilters, fine filters,
Ing. Antońın Engel.

1 Introduction to the problem

In the 1920s Prague was faced with a crucial prob-
lem—howto provide drinkablewater for the inhabi-
tants of the city.
Although there was a new system based on the

newly constructed water plant in Káraný, Prague
needed more water than this new source was able
to provide.
The water plant was modernized and expanded

but the amount of water that could be drawn was
inadequate. New ideas about new resourceswere put
forward, but nothing changed until the end of the
1920s, when the new water plant was built next to
the Vltava river in Podoĺı.

2 Prague’s water supply
system

In 1913, just before the demise of the Austro-
Hungarian monarchy, Prague finally completed the
long proclaimed project of building of a new water
supply system thatwas able to transport cleanwater
to the biggest city in the Czech lands. The project
was completed just in time. The first world war was
imminent, andwithout this source of cleanwater the
citizens of Prague would have suffered more health
problems than they did.
However, shortly after the first world war ended,

problems of water supply again came into the fore-
ground. Prague, the capital city of the newly es-
tablished republic, was enlarged and combined with
its suburbs. The now increased number of inhabi-
tants were in urgent need of clean water. The newly
constructed water supply plant was suddenly inade-

quate, and the city authorities began to look for a
solution.
The systemthatwas supplyingPraguewith clean

water after the first world war was based on four
sources,which suppliedwater of varyingquality. The
main source was the new water plant in Káraný,
which delivered water only to the inner city and the
inner suburbs. The second biggest water source was
infiltrated water from the Vltava river (the infiltra-
tionwasmixedwithwater fromKáraný). Thewater
plant was located in Bráńık (this water plant was
founded in 1876). Water from this source was deliv-
ered into just two other city districts. Both of these
sources were capable of supplying water suitable for
drinking.
The third and fourth sources were both from the

Vltava. The river provided water for the factories
around the city (many of them had their own wa-
ter plants) and for the water wells that were located
throughout the city. Both of thesewater sources sup-
plied water that was not suitable for drinking.
The main water source was still Káraný, and the

city fathers were working on providing enough wa-
ter from Káraný to supply the whole city. Despite
the modernization works, Ing. Jaroslav Vancl, head
of the water department in the Technical Office of
the city, set up a project for future extension of the
water supplies.

2.1 Water plant in Káraný

The water plant was first set up in 1905, and was
finally completed in 1913. The plant was planned
only for the inhabitants of inner Prague and the sur-
rounding suburbs. It was planned to supply only 120
l per day and per person. By the end of the war, the
amount of water that was supplied had risen to 170 l

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Acta Polytechnica Vol. 51 No. 5/2011

per day andper person, but the dilapidatedpipelines
also led to considerable losses.
During the 1920s, the capacity of the plant was

enlarged to its final amount of 80000 m3 per day.
However, this was not enough, because the numbers
of people connected to the water plant kept growing,
as did the amount of water used per person to 200 l
per day.

Fig. 1: The water plant in Káraný

2.2 The Plan of Ing. Jaroslav Vancl

In 1921, Ing. J. Vancl presented a plan to the city
council. He had evaluated the development of the
city, the growing number of inhabitants and the in-
crease in the water drained from Káraný, and made
a forecast for the next 70 years.
His answer to the growing needs for more water

was to build dual water pipelines to Prague, and to
build more water plants to collect more water.
The dual pipelines were planned to supply water

of twodifferent types. Drinkablewaterwouldbe sup-
plied from Káraný, and non-potable water would be
taken from the Vltava, which could provide a suffi-
cient amount of water for the needs of the city.
Ing. J. Vancl planned to bring 130 l of water per

day and per person into the city. Only 50 l would be
drinkable and drawn from Káraný. The rest (80 l)
would be drawn from the Vltava.
A new water plant was planned to the south of

the capital, in the village of Štěchovice. A huge dam
would be constructed there, according to the Ameri-
can model.
Themain problemswhich prevented this plan be-

ing implemented were the enormous cost (770 mil.
Kč to build all the dual pipelines and the dam) and
the risks of bringing unclean water into the houses
in Prague. Nobody could guarantee that the inhabi-
tants would not drink this water.

3 Podoĺı water supply plant

While the city councilwas still assessingVancl’s plan,
the situation in the Prague was slowly becoming
worse and worse.
In 1923, irrespective of Vancl’s plan, the city

council decided to build a new water supply plant,
which would supplement the water brought to the
city from Káraný.

Fig. 2: The facade of the filtration building

Fig. 3: Location of the water supply plant

The new plant was located in Podoĺı. Two water
plants had been located in Podoĺı in the past, and
the city council decided it was a suitable place for a
new plant.

3.1 Dispositions

Thetwooldwaterplants inPodoĺıwereboth founded
in the 1880s. Onebelonged to the townofVinohrady
(a suburbwith the status of a town), while the other
belonged to the city of Prague.
In the early 1920s, several tests were carried out

to find the chemical composition of the underground
water, which was planned to be the main source of
drinkablewater. Unfortunately, theundergroundwa-
ter was found to contain too much iron and man-
ganese, and the water was also too hard.
The solutionwas to use the groundwater andmix

it with river water. To collect ground water, the old
system of collecting wells was used. They were dug
on Schwarzenberg Island (now called the Rowing Is-
land). The wells were built with an average length
of 4 m, depth 6.50 m, and were placed 4 m under
the surface of the island. They were connected to
the water plant by a drainage pipe. All the machin-
ery was newly rebuilt. The river water was taken
through the newly built riverbed located next to the
old water plant formerly belonging to Vinohrady.
Because of the moderate quality of the river wa-

ter, the builders had to construct a sophisticated fil-
tration system, which had been proposed by Vancl.
It was decided to use the Puech-Chabal system, and
a contract with Chabal & Cie. was signed in 1921.
This system was considered as one of the best, and
the city alreadyhad good experiencewith it as it had
been used at the Institute for the Insane at Bohnice.

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Acta Polytechnica Vol. 51 No. 5/2011

Fig. 4: Scheme for taking water from the Vltava

The filtration system was planned to have a maxi-
mum capacity of 35000 m3 of water per day.

3.2 Construction

In 1922, when the plans for the filtration plant had
come from Chabal & Cie., Prague also received the
plans for constructing the water plant. These were
just simple plans for the facade, and thewhole build-
ingwas a simple structure. The skeleton of the build-
ing was based on a roof structure comprising vaults
with a margin of 6.50 m, which formed twelve longi-
tudinal fields.
As the project was developed, the original plans

for the building were found to be inadequate, and
a tender for the architectural design of the building
was announced. The winner of the competition was
Ing. Antońın Engel.
Engel proposed to build in stages,with each stage

supported by a system of columns. Later, because
the columns made the system too complex and too
confusing,Engel changed theplansanddeviseda sys-
tem of parabolic arches. These arches had a margin
of 24 m, and the biggest arch above the prefilters
was 16 m in height. For this system, one huge hall
60×24m in size was constructed in the water plant.
The system was designed by Prof. Ing. Frantǐsek

Klokner and Ing.Dr. Bohumil Hacar, who alsomade
the calculations.
Further changes were made when Ing. A. Engel

designed the windows and addressed the problem of
sufficient sunlight. The original windows were too
small, and they were replaced by squared windows
over the whole area of the walls.
The buildingwas almost completelymade of con-

crete, and was one of the biggest concrete structures
in the whole of Czechoslovakia.
The entire complex of thewater plantwas to con-

sist of four buildings — two filtration plants, one en-
gine chamber and the administrativebuilding. In the
original project, only the first filtration plant (the
northern one) and the two other support buildings
were constructed.
The whole complex cost Kč 17316039.

Fig. 5: The change in the architectural design of the
building

3.3 Filtration system

The system consisted of four levels:
• large mesh filters
• prefilters
• fine filters
• tanks for clean water.
Because of a lack of space in the water plant, it

was decided to stack the levels above each other, and
not to place them side-by-side, as was normal in the
Puech-Chabal system.
The large mesh filters and the prefilters were on

the top floor, the fine filters were on the ground floor
and the tanks for clean water were located in the
basement.
The filters are divided into twelve parts, and the

whole system is divided into two halves with an ex-
pansion joint in the longitudinal direction and also in
the transverse direction.
Raw water is taken from the river and from the

collecting wells through the engine building to the
filtration building.

Fig. 6: Scheme of the pipelines heading from the engine
building to the filtration building

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Acta Polytechnica Vol. 51 No. 5/2011

Fig. 7: Longitudinal scheme of the filters

Fig. 8: Scheme of water production

3.3.1 Filters

The system of the filters is quite simple. Sand and
gravel is put into a system of filtration beds (54 cm
in length and 7 cm in height) with 64 holes that ex-
pand conically. The water flows through the holes to
the bottom of the filter and then to the small cham-
ber that collects the water before it flows down the
cascade to the next level of the filtration.

Fig. 9: Scheme of the filtration beds

3.3.2 Large mesh filters

Thefirst level of filtration comprised three degrees to
ensure complete removal of gross contaminants. The
degrees of filtration were located above each other,
like the rest of the filters.

Table 1: Parameters of the large mesh filters

First degree of large mesh filters

Floor space 259.30 m3

Height of the filter 35 cm

Grain size 2–2.5 cm

Speed of filtration 116 m3/ 24 hrs

Second degree of large mesh filters

Floor space 404 m3

Height of the filter 40 cm

Grain size 1–2 cm

Speed of filtration 74 m3/24 hrs

Third degree of large mesh filters

Floor space 1371 m3

Height of the filter 50 cm

Grain size 5–10 mm

Speed of filtration 22 m3/24 hrs

The first degree is supplied with unfiltered wa-
ter from the doubled feeder channel, which has sep-
arated space for groundwater and for river water
(the channel for the river water is enclosed, while
the groundwater channel is open). At the expansion
joint, the channel is connected with an iron pipeline
with Gibault system expansion joints.
The water falls from the channel to the first de-

gree from the squared hole located 7 cm below the
water level in the channel. From the first degree, the
water falls to the second degree and finally to the
third degree of largemesh filters. In each degree, the
water level above the gravel filter is about 75 cm.
Each step is separated from the others by awater

cascade, which helps to oxidate the water. The cas-
cades between each degree are 30 cm in height, and
the difference in water level between the first degree
and the third degree is 2.10 m.
The coarse sediments are removed in the large

mesh filters. They are sedimented on the surface of
the filters. This is the active part of the cleaning
process.

3.3.3 Prefilters

The prefilters are also divided into six parts with an
extension joint. However, due to the huge floor space

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Acta Polytechnica Vol. 51 No. 5/2011

they are also divided into two further parts. There
are six prefilters on each side in two lines, with three
prefilters located in each line, one behind the other.

Fig. 10: Scheme of the filters

Table 2: Parameters of the prefilters

Prefilters

Floor space 2625 m3

Height of the filter 70 cm

Grain size Up to 7 mm

Speed of filtration 11.4 m3/24 hrs

The activewater treatment system is the same as
in the large mesh filters. The process and the filters
in the prefilters are of course finer than before. The
prefilters and their sand filters are also themain part
of the filtration.
Themembrane on the prefilters ismade fromfine

colloidal suspensions, which are taken from the wa-
ter. To accelerate the formation of the membrane,
unfiltered water can also be drawn from the large
mesh filters.

Fig. 11: Scheme of the fountains

3.3.4 Fine filters and tanks for clean water

The fine filters are the last level of the filtration pro-
cess. They are located on thewhole groundfloor area

and the prefiltered water is brought there by a sys-
tem of fountains, making a use of the big differences
in height between the prefilters and the fine filters.

Table 3: Parameters of the fine filters

Fine filters

Floor space 5604 m3

Height of the filter 90 cm

Grain size Up to 4 mm

Speed of filtration 5.3 m3/24 hrs

The fountains are an important part of the oxi-
dation of the water. Together with the cascades be-
tween all levels of the filters, the accelerate thewater
cleaning process.
All twelve parts of the fine filters have their own

longitudinal groove. This groove collects the final
product, filtered water, and leads to the pipelines
that takes the water into the collecting tanks.

Fig. 12: Plan of the fine filters

The tanks for clean water have a capacity of
15000 m3 of water. This volume was chosen so that
water will be available even if the machines taking
thewater to the final areaswork only 16 hours a day.
Thiswasdone to avoidoperating themachines in the
daytime, when electricity is most expensive.
The tanks are divided into four parts, and the

water always flows because of the heading and suc-
tioning pipelines, which are located 52 m apart.

3.4 After completion, and the
present-day situation

The water from the Podoĺı water plant entered
Prague’swater supply systemjust in time. Thewhole
project was constructed between 1923 and 1929, and
in the final year the consumption of drinking wa-
ter reached almost 200 l per day and per person.
The water was to undergo biological tests lasting
3–4months, but there was no time to perform these.

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The water plant was completed in March 1929.
From May the water was drawn into Prague’s
pipelines with water from Káraný, even though this
had not been part of the plan. The plan had been
to use water from the Vltava only as non-drinking
water.
More recently, water from the river has been

drawn into its own water tank in Flora, which was
connected with the old water tank for water from
Káraný. The connection for mixing those two differ-
ent kinds ofwaterwas used onlywhen that therewas
an inadequate stock of drinkable water.
In the 1950s, the consumptionofwater roseagain,

and even with modernization and improvements of
the engines the water supply plant was not able to
meet the increasing requirements. As a result, the
city council decided to built on to the water plant.
Engel was again chosen as the leading architect,

and he was given an opportunity to complete his
project in terms of his old plans.
The building was constructed between 1957 and

1965, but from 1960 onward the unfinished water
plant started to provide water for Prague’s pipelines
and became Prague’s main source of water supply.
The water plant was in use until the great floods

in 2002. Altough the water plant was not impacted
by the floods thanks to Engel’s good planning, it
was withdrawn from the Prague system. It is now
a standbywater plant for use if themainwater plant
in Želivka is out of order.

Acknowledgement

The research presented in this paper was supervised
by Prof. I. Jakubec, Faculty of Arts, Charles Univer-
sity in Prague and was supported by research pro-
gramme No. 263101 “Man in the perspective of his-
torical science”.

References

[1] Jásek, J.&col.: Water supply plant inPodoĺı and
Antońın Engel. Prague 2002.

[2] Sńıžek,E.: The newwater supply plant in Podoĺı
and its water engineering and architectural de-
velopment,The Technical Horizon — The Maga-
zine of Czechoslovakian Engineers, 1928, vol. 36,
pp. 360–440.

[3] Červenka,V.: FiltrationStation inLand Institute
inBohnice.Gas and Water, 1928, vol.8, no. 7–8,
pp. 168–170.

[4] Archive of Prague’s Waterworks and Sewer-
age (APVK), Prague Waterworks fund, panels
140–149.

About the author

Kryštof Drnek was born in Prague in 1985. He
graduated from the Faculty of Arts, Charles Univer-
sity in Prague with a bachelor degree in 2007, and
with amaster degree in 2010. Since then he has been
studying for a PhDdegree in economic history in the
Department of Economic History at the Faculty of
Arts, Charles University in Prague.

Mgr. Kryštof Drnek
E-mail: drnekk@gmail.com
Dept. of Economic and Social History
Charles University in Prague
Náměst́ı Jana Palacha 2, 116 38 Praha 1,
Czech Republic

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