Hydrant Minimum Pressure

[Saber Elkassas]

Hello,

I have a concern regarding the minimum hydrant residual pressure. as per IFC and NFPA, it is clearly mentioned as a 20 psi .. but some designers are considering 100 psi .. should that 100 psi has any code reference?

 

[cda]

Not sure where they get 100

It is more up to the authority having jurisdiction as to minimum,,
But normally the ahj is the water supplier

 

[cda]

Your not mixing fire hydrants with something else??

 

[TheCommish]

From the firefighting and booster pump perspective 20 PSI is the minimum pressure at the suction side of a pump, for it's proper operatin and damage to it and public water system. Flow and pressure are related, however I cannot make flow, I can make pressuer with a pump. A large main with sufficant flow (supply) can have the presure increasd by a pump to 100 PSI or more wiht the output GPM limited by the supply. A small main wiht hight pressue is limit by the flow of the supply and piping sytesm.

 

[Msradell]

From the firefighting and booster pump perspective 20 PSI is the minimum pressure at the suction side of a pump, for it's proper operation and damage to it and public water system.

While that's certainly ideal many of us who have spent much time in the fire service can tell you that that's not obtainable many times when you are trying to flow large amounts of water. As long as you have a good pump operator you can easily reduce the inlet pressure to 10 psi, I've even seen it pulled down to 5 psi and work fine with a good pump operator and a steamer connection (I've even seen hard searching used but we don't want to talk about that).

 

[TheCommish]

While that's certainly ideal many of us who have spent much time in the fire service can tell you that that's not obtainable many times when you are trying to flow large amounts of water. As long as you have a good pump operator you can easily reduce the inlet pressure to 10 psi, I've even seen it pulled down to 5 psi and work fine with a good pump operator and a steamer connection (I've even seen hard searching used but we don't want to talk about that).

that is true and obtainable on some municipal systems with skilled pump operators, on some systems 20 psi is difficult for it to handle

 

[Saber Elkassas]

Hello,
Thanks for these fruitful discussion but I can see that there is no clear reference for this 100 psi and always we have to consider 20 psi for hydrant residual pressure.