Potable Water Storage &
Distribution Systems
1:37 PM
Water Storage Tanks
Parts of bird
removed from a
potable water
storage tank on a rig
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Water Storage Tanks
Unorthodox Day
Tank & Pressure set
1:37 PM
Water Storage
• All water tanks should be inspected
on a yearly basis
• Keep the tanks clean All water tanks
should be free from Corrosion and
Sediment
• Maintain Free Chlorine levels
between 0.2 to 0.5 ppm
• Don’t transfer drill water into
potable water tanks
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Water Storage Tanks
Dirty tanks can
contaminate clean
bunkered water.
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Water Storage – Tank Entry
Breaking containment of a potable water tank should be planned carefully
• Avoid breaking containment if working on sewage
systems or pipe work in same area.
• Avoid breaking containment if working on chemical
or fuel systems or pipework in same area.
• Avoid breaking containment if you do not have the
chemicals available to disinfect the tank post entry
(also are the chemicals in date).
• If plans change reassess the risks to tank
contamination from other work in and around the
tank area
1:37 PM
Water Storage – Tank Entry
Good hygiene should be observed
• Consider the area around the tank
• Consider the tank access
• Consider the other work going on around
the tank
1:37 PM
Water Storage – Tank Entry
Good hygiene should be observed
• Consider the area around the tank
Is there sewage plant nearby that could contaminate
the tank when open.
If the tank access is through the deck should floor
be disinfected before breaking tank containment.
Are there fluid/water leaks around the tank hatch.
1:37 PM
Water Storage – Tank Entry
Good hygiene should be observed
• Consider the area around the tank
Is the tank in an area that there is likely to
be an open deck hatch that can allow rain to
wash debris into the tank ?
1:37 PM
Water Storage – Tank Entry
Good hygiene should be observed
• Consider the tank access
• Is the tank access hatch recessed
into the deck – high risk from leaks
or spills !
1:37 PM
Water Storage – Tank Entry
Good hygiene should be observed
• Consider the other work going on
around the tank
Will other work be carried out near open
pot water tanks ?
Emptying bilge tanks/cleaning tanks ?
Work on sewage systems ?
1:37 PM
Water Storage – Tank Entry
Good hygiene should be observed
• No Dirty clothing or foot ware to be worn in
tanks. Clothing should not been used for any
other work area
• Maintain a clean changing area around tank
• Disposable Boiler suits, disposable gloves
and masks and new wellies to be worn
• Clean equipment to be used preferably new
each time
1:37 PM
Water Storage – Tank Entry
Good hygiene should be observed
• Suggest using foot bath tray with
hypochlorite solution (250ppm) to
disinfect wellies before tank entry.
• Alternatively use spray bottle to
thoroughly disinfect the outside of
the wellie boot
1:37 PM
Water Storage – Tank Cleaning pumps/hoses
Good hygiene should be observed
• Best to use new pumps and New
hoses.
• Suggest disinfect pumps before use
(250 ppm hypochlorite)
• When hoses not in use Bag ends of
hose to prevent contamination
• Lock away clean hoses and pumps for
use in pot water tanks during
shipyard to prevent contamination
• Think about pump placement and
type of pump – tank entry post clean
to remove submersible pump ?
1:37 PM
Water Storage – Tank Entry
Good hygiene should be observed
• Medic can vet people entering
tanks – no colds / flu /stomach
problems. Workers should not be
suffering from any skin infection or
communicable disorder.
1:37 PM
You have persistent diarrhoea
You are suffering from persistent vomiting
You have a prolonged unexplained fever
You have jaundice or hepatitis
You have dysentery
You or a member of your family have been diagnosed with
typhoid/paratyphoid or have a prolonged fever
Do not work on restricted operations if
:
In these cases report to your supervisor
You pose a risk to water quality!
1:37 PM
Water Storage – Chlorination Post Tank Entry
• Following tank entry it is good
practice to disinfect the tank.
• This is best done by chlorinating the
tank to between 50 ppm free
chlorine for a period of 12 hours.
• The Hypochlorite should be added
when the tank is between 10 – 25%
full to allow the filling to mix in the
hypo
• This chlorinated solution can be
neutralised by dosing the tank with
sodium thiosuplhate.
1:37 PM
Water Storage – Chlorination Post Tank coating
If a tank has been re-coated /
painted it is good practice to
completely fill the tank during
chlorination so that the surface
of the tank is treated.
It is common for some solvent
release post coating into the
water. This often happens
when rigs move and water gets
splashed onto the roof of the
tanks.
Complaints about funny tasting
water during rough weather?
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Water Storage – Chlorination Post Tank Entry
• Try to maintain the
chlorine levels in the tank
at 0.5 ppm in the week
following the disinfection
1:37 PM
Water Storage – Sight Glass Contamination
Sight glasses are potential sources of
contamination as bacteria growing within the
sight glass wash back into the tank as the level
drops.
How often do you see a clean sight Glass ?
1:37 PM
Water Storage – Sounding Tape Contamination
If using Sounding tapes you should soak the entire
tape apparatus in a solution of 100-ppm Free Chlorine
solution for 2 minutes.
The tape should be stored in a clean storage box . The
color cut paste should be wiped off with a clean cloth
or paper towel
1:37 PM
Water Storage – Dip Stick contamination
Wooden Dip sticks are potentially great
sources of contamination
Replace with Sounding Tapes
(and keep them clean)
or
Better still use electronic level measurement
1:37 PM
Hot Water Temperature – Part of Control System
1:37 PM
Temperature
Critical Parameter
70 -80
o
C (158
– 176
o
F)
Pasteurisation ( disinfection ) range
66
o
C (151
o
F)
Dead within two minutes
60
o
C (140
o
F)
Dead within 32 minutes
55
o
C (131
o
F)
Dead within five / Six hours
35
– 46
o
C (95
– 115
o
F)
Proposed optimum growth range
20
– 50
o
C (68
– 122
o
F)
Growth can proceed
Below 20
o
C (68
o
F)
Dormant ( No Growth)
Controlling Bacteria – Hot Water Temperature
1:37 PM
Calorifiers
•
Pipework should be insulated to minimise heat transference.
•
Good condition, no rust, corrosion.
•
Accessible & Safe drain point on Each Calorifier
•
Temperature Gauges on Each Calorifier Outlet
•
Temperature Gauge on Hot Water Ring Main Return
•
If you have a Shunt Pump – use it
1:37 PM
Calorifiers / Hot Water Heaters
Assess risk of potential contamination
from waste heat systems. Inspections
to assess corrosion of heat exchanger
or coils
Pipework of old systems can perforate
and Glycol and corrosion inhibitors can
get into the hot water
1:37 PM
Calorifiers
•
Pipework should be insulated to minimise heat transference.
1:37 PM
Rust & sediment
accumulation at
bottom of Calorifier.
Rust from Carbon steel
pipework
Calorifiers
Maintained in
good Condition
1:37 PM
Calorifiers
Mini Settling
Tanks
1:37 PM
Calorifiers – Temperature Gauges
•
Temperature Gauges on Each Calorifier Outlet
•
Temperature Gauge on Hot Water Ring Main Return
1:37 PM
Calorifiers – Drain valves
•
Accessible & Safe drain point on Each Calorifier
Good
– drain valve accessible
and good access to drain
BAD
– drain valve not easily
accessible and no access to drain
1:37 PM
Calorifiers
Shunt Pumps
Shunt Pumps can be used to ensure
that there is no dead areas within
the Calorifiers. More common with
older sites with larger Hot water
tanks
1:37 PM
Calorifiers
• Purge ALL Calorifier Drain Points WEEKLY
1:37 PM
Calorifier -
Management
• Before bringing Calorifiers back on line
inspect interior and flush out any debris /
Sludge.
• Before bringing Calorifiers on line after
repairs – Carry out a thermal disinfection
for one hour at 70°C.
1:37 PM
Calorifier -
Management
Pasteurisation of Calorifiers/Hot Water Systems
Before bringing the tanks back on-line the tank should be drained of any stagnant
water and an internal inspection carried out.
Any sediment/rust should be flushed out of the Calorifier before refilling and
carrying out a thermal disinfection.
1:37 PM
Pasteurisation of Calorifiers/Hot Water Systems
1. The Calorifier must be filled and isolated from the main system by closing the Hot Water flow
and return valves to the tank & the cold feed valve to the tank. Fit warning signage to the
calorifier tank or valves to ensure that personnel know it should be kept isolated from the main
system till the disinfection is completed.
2. The de-stratification (shunt) pump is to be put in manual override to run continuously (if
fitted).
3. The temperature control thermostat to be raised to 75 deg C.
4. On reaching the higher temperature, this must be maintained for one hour.
5. Reset temperature control thermostat to 60 -70 deg.C & return destratification pump (if
fitted) to automatic (timed) control.
6. Allow system to return to normal operating temperature & remove any warning signage put in
place.
7. Open cold feed valve and hot water exit valve and return the system to normal operation.
1:37 PM
Pipework Replacement
The type of pipework on site could have
an influence on what grows in the
potable water systems.
Some pipework may lead to higher
bacteria growth
1:37 PM
Pipework Replacement
If you replace your copper pipework with plastic silver
ion disinfection may no longer work as the silver
works in combination with copper in the system.
1:37 PM
Pipework or Valve Replacement
New Materials / New Parts
The internal surfaces of all new pipe, valves, connectors,
and other items of equipment that will be inserted into
potable water lines are to be steeped in a 50 ppm solution
of Sodium Hypochlorite for 60 minutes immediately
prior to use.
1:37 PM
Pipework or Valve Replacement
Existing Materials
The open ends of pipe work or valves or connectors in the
existing potable water system will be treated with a 1%
solution of Sodium Hypochlorite or by wiping with alcohol
impregnated tissue immediately after the pipework
has been opened.
The open ends will then be sealed using clean polythene
bags and tape. Immediately prior to inserting the new spool
or other piece of equipment, the polythene bags will be
removed and the open ends of the pipe work will
be disinfected again.
1:37 PM
Pipework or System maintenance
Worksite cleanliness – close off
or bag open pipe ends
Segregation of equipment if
working on clean water and
sewage operations
Small fittings - clean & bagged
1:37 PM
1000
L
a
te
x
Legionella and supporting
flora were grown in
continuous culture model
systems.
Counts are expressed as a
ratio relative to the counts
on glass (=1)
e.g. there was approximately
10 X the growth of aerobic
heterotrophs on cPVC as
there was on glass.
C
op
pe
r
Heterotrophs
Legionella
E
th
-p
ro
p
G
la
s
s
cP
V
C
uP
V
C
Poly
eth
P
oly
bu
t
P
o
ly
p
ro
p
Gro
wth
R
elative
to G
las
s
100
10
1.0
0.1
Conclusion: higher flexibility of plastic generally correlates with increased
support for growth
Growth on different plumbing materials
relative to glass (=1)
1:37 PM
Dead Legs
Identify any dead ends in their potable water system and take action to eradicate them
1:37 PM
Managing the segregation and
isolation of potable water systems on
offshore installations
1:37 PM
Water Storage Tanks
Main Storage Tanks
Hydrophore
Calorifiers
To Accommodation
To Accommodation
1:37 PM
Water Storage Tanks
To Accomodation
1:37 PM
Water Storage Tanks
1:37 PM
Water Storage Tanks
Main Storage Tanks
Hydrophore
Calorifiers
To Accommodation
To Accommodation
Day Tank
1:37 PM
Water Storage Tanks
Main Storage Tanks
Calorifiers
To Accommodation
To Accommodation
Header
Tank
1:37 PM
Water Storage Tanks
Main Storage Tanks
• Water storage Tanks must not be
run in parallel
If re-coating water storage tanks ensure it is done correctly. Ensure tanks are
disinfected before use.
Also get water samples checked for Hydrocarbon & bacteria levels before
bringing tanks on line to accommodation
1:37 PM
Water Storage Tanks
Day Tanks and Header tanks should be sized or managed so that
they are turned over a minimum of every 24 hours
Day tanks & Header tanks offer the potential for chlorine dosing
equipment triggered by the transfer pump. Pump must be
interlocked so that they shut down when the pump is not
running
1:37 PM
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