Water hammer arrestor
Pressure reducing valve
Water drain cock
Calculation of the loop's
pump flow capacity =
The flow is calculated according to calorific losses on the
surface of the whole piping, it depends on the thickness of the
Loss "P" :
P = L.k. (te - ta) P in w, L in m,
K : coef k (insulating)
(this coefficient varies according to the diameter
and the nature of the pipe),
t e : temperature of sanitary hot water,
t a : room temperature
(for example : +10°C in the basement, +20°C upstairs).
This discharge is usually determined according to a
T near 5°C.
t r : temperature of the return, will never be less than 50°C.
td : starting temperature.
1,163 (td - tr)
Q (m3/h) = _____________
Key points of the regulation :
- Increased hot temperature from the heater (use water heaters with minimal or no
- Use of recirculation systems : circulating loop and balancing valves
- Ensure that the target temperature is achieved throughout all levels of the loop.
- Circulating loop should be designed to return the mixed water to the storage not
less than 55°C*.
- Mixing valves must be as close as possible to the point of use.
- Mixing valves must have integrated check-valves.
- Mixing valves must allow easy cleaning and disinfection operation.
- Dismantle and clean hoses, tap, showerheads and mixing valves minimum once a
- Hot and cold water distribution pipes must be insulated sufficiently (never together).
* according to National Regulation
Flow diagram for a "multi-levels"
complete mixed water circuit
VM : micrometer valves to stabilize
VM1 A : Open between 70 and 90%.
VM1 B : Open between 30 and 10%.
Remark : If there is a connection point on the boiler (R) the return circuit
should be connected here (A).
Recycling of the loop : with a minimum of six times
the mixed water's volume per hour.
Delivery of the pump : total manometric height,
minimum 4 meters + head loss of the loop.
THE " MULTI-LEVELS " APPROACH
THE RIGHT TEMPERATURE FOR EACH APPLICATION
Development of legionella according to water temperature
<20°C / 69°F
20-46°C / 68-115°F
growth (no multiplication from 47°C on)
50°C / 122°F
90% of bacteria will die in a period of 2 hours
60°C / 140°F
90% of bacteria will die in 2 minutes
80°C / 178°F
90% of bacteria will die in less of 1 minute
Relation between the canalization's capacity and its length *
Dimensions of the pipe Length in meters leading to
a capacity of 3 litres
15 x 1
18 x 1
22 x 1
Plastic pipe PEX/PER
15 x 2,5
18 x 2,5
20 x 1,9
25 x 1,9
*Source : CSTC Belgium Nov. 2002. The canalization's capacity is the inner section
multiplied by the length.
Please also consult the calculation model and practical rules on page 7.
according to National Regulation
Volume inferior or equal to 3
litres between the
distribution point and the
most distant point of use
(shower), see table 2.