Water New Zealand Web Forum

[WTRBOY]

Greetings All
Table 2 in this code confuses me in relation to whether fire-fighting storage is required or not for a reticulated system.

For instance Fire Water Classification FW3 (typically applying to small firecells for light commercial) requires 25 l/s within 135m plus a further 25 l/s within 270m ie 50 l/s total.

The 2 right hand columns of the table indicate a storage volume requried of 180m3(which is 50l/s for 60 mins) but this requirement appears to relate only to non-reticulated supplies. However Note 6 under the table requires an "alternative source" if this volume is not available from the reticulated system.

Appendix K specifically talks about fire supply storage for reticulated systems but does not specifically refer to the volumes in Table 2 or any other requirement. K2 says that this volume must be in addition to normal operating storage and provision for "normal system failures", the only exception being a civil defence emergency. If you normally size the reservoir for 1 day's average demand does this include the fire storage or is that on top ?? However the 1 day rule (or 2 if you like big reservoirs) is pretty arbitrary to start with unless you have done a full demand and risk assessment.

Question - what provision are you including in reservoir sizing for fire supply ? Do you take into account the top-up flowrate for the reservoir when doing that ?