Water New Zealand Web Forum

[Petrina]

Do any other Local Authority's have issues with buildings internal fire sprinkler systems and sub-standard water pressure due to an increase in demand during the day? Fire hydrant flows surrounding the problem area are to standard so we are looking at booster pump systems. Anyone have other ideas?

[Dylan Stuijt]

Hi Petrina

This is becoming a very common problem around the country, particularly now that many councils are implementing pressure reduction in response to source water constraints, and the need to demonstrate efficient use of water.

The feedback I've received from other water supply managers, and from my own experience, is that the fire design industry have historically logged the pressure on the existing main (potentially during the best pressure period), and used this to design the system, and in 99.9% of the cases they've made no contact with the water supply authority regarding minimum system pressures, diurnal patterns, or a suppliers long term plans. Our minimum stated level of service is 300Kpa, and this would be the starting point for any discussions with the fire designer (regardless if our actual pressures get up to 800Kpa). In many areas we are looking to reduce/stabilise pressures to around 500Kpa, and I know there are some sprinkler systems in that zone which are designed for a minimum of 650Kpa. We will be talking directly with these properties to help resolve the issue, but ultimately someone made a design decision that was independent of the water supply authorities input.

This has been raised directly with senior management at the fire department on a number of occasions, and I think the message is getting through that designers need to contact the water supply authority before they commence a design.

Once a system is sized in installed, it’s very difficult to change. I've seen the odd system retrofitted with storage and a re-booster pump.
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Water Supply Manager - Hastings District Council

[Graemem]

Hi Petrina

Are you referring to domestic home sprinkler systems or commercial/industrial dedicated systems? If you refer to the latter, yes there are inherent problems with fire companies designing a system to the current mains pressure and NOT to the customers service level. And when there is a problem it inevitably become Councils and not the designer. We have also experienced issues when we are retrofitting backflow devices on dedicated fire systems. Because there can be up to 4 Kpa pressure drop across a device, if the fire system has been designed with very find pressure tolerances there may not be sufficent pressure to operate the fire system. Again this is always appears to be Councils problem.

Regards