PowerSpout
React Pump Installation
© 2019 EcoInnovation Ltd (NZ) V2.1
Page 88
So the calculated head is 82m static lift + 11.2m pipe friction head =
93.2m
. Headloss is
about 14%, this is less than the 20% we initially allowed for so all is well. If it was over 20%
we would need to go up another pipe size.
Let us now look at a 20NB pipe example for comparison
Pipe needed
Pipe ID mm
Friction head per
100m roll
Total
2 x 200m roll of 125m
rated pipe
21mm MDPE
3.6m
4.4m
2 x 200m rolls of 90m
rated pipe
22mm MDPE
2.9m
3.6m
1 x 200m rolls of 80m
rated pipe
20mm LDPE
4.5m
3.2m
Pipe friction head
35m
So the calculated head is 82m static lift + 35m pipe friction head =
117m
. Headloss for
20mm pipe is about 42%
The reality is that pumping to 93.2m or 117m would not make a large difference in the L/day
yield for the following reasons:
Pipe flow will rarely be at 15L/min (so friction head is less in reality), this reduces the
dynamic head on the smaller pipe to a greater extent than the larger pipe.
Pump is more efficient on higher lifts.
So in the end it all depends on the relative pipe cost while taking account of the fact that
pipes will higher losses may require a higher pressure rating. If the quote for the 1000m of
20NB pipe is much less than the 25NB pipe then maybe go for the cheapest option. If there
is say less than 20% in it go for the larger pipe. The larger pipe does keep your future
options open.
If in doubt (and funds are available) we would always recommend using a larger pipe size,
given that pipes will become fouled over time and so the headloss will increase. A decision
must be made based on:
the required flow rate
the relative costs of pipe at the calculated dynamic pressure
your future options
Onsite flow test (25 NB)
6.2.2.
On a typical day at midday in January we measured 20 litres in 80s = 15 l/min
