Hydraulic Calculations 1

[Ketzal]

Hello Everyone..this is my first time here and what I have read so far is pretty impressive.
I have just started as a fire protection designer. I have very limited knowledge about this industry. I was wondering if you can help me with a project I am currently working on.
It is a Wellness center (Mix occupancy A-1, A-3, B), it has two swimming pools, tracks, gym, small auditorium, therapy exam rooms, general spaces (offices, conference rooms etc).
General information about this building:
>2 stories = Garden Level (-15 ft), Main Level (+18 ft)
>44 static, 42 residual, 940gpm flowing a 2.5" nozzle
>112,000 square feet (55,000+ square feet per floor)
>Standpipe is not required since building is a single story

I am trying to calculate whether or not I need a fire pump or is the street water pressure sufficient to exclude the fire pump. This is what I calculayed.
>I am assuming this will be a light Hazard building (Am I correct?)
>8" CI imcoming water line (300 feet) = 0.1 psi
>RPZ = 11 psi
>8" pipe after RPZ (30 feet (header for sprinkler risers)) = 0.01 psi
>4" pipe from garden level to most remote area on Main level (565 feet + 170 feet for fittings = 73ft) = 9.2 psi
>Elevation is 18ft x .433 = 7.8psi
>Sprinkler, using 13 gpm (LH), k=8.0 this gives me = 2.6 psi

For a total of 31 psi I am still below the city water curve....So I came to the conclusion I do not need a fire pump.

Did I do this correctly? Am I missing somthing in my calcs?

Any advice would be greatly appreciated....

Thank you very much

 

[chicopee]

Since you did not get much of a drop in pressure when you tested the water supply at the nearby fire hydrants, I would have flowed two nozzles for a greater accuracy on you water main test.

 

[chicopee]

I am using a hydraulic graph to plot your results and looking at "4" pipe from garden level to most remote area on Main level (565 feet + 170 feet for fittings = 73ft) = 9.2 psi", how did you get 73 feet for the 4" line and the fittings when you add 565 and 170 feet? At what flow rate did you get your pressure drops? Right now based on a 4" 735 feet line length being the most remote point, I am getting approximately 250 gpm at a line height of 18 feet and assuming a RPZ backflow preventer loss of 11 psi at any flow.

 

[chicopee]

Is this a 4" RPZ?

 

[Ketzal]

Chicopee....Thanks for getting back....
Your first point: Unfortunately that was the infromation provided to me by the Civil engineer. Do you think I should ask for another hydrant flow test then?

Your second point: I typed the wrong number...you are correct it should be a total of 735 feet (pipe length and fittings)I The flow rate I calculated (0.10gpm x 1500ft=150gpm) I added 30% to 150gpm which gave me 195 gpm. So I used 195 gpm for the flow rate. I chose the 8" RZP based on 195 gpm flow.

Your third point: Current desig is for an 8" RPZ...I was thinking of having an 8" header where 4 alarm check valves can be manifolded. That way I can have each floor divided into two zones. I designed for each alarm check valve to be 4" so that a 4" main can be routed to the most remote area.

Again thank you

 

[chicopee]

I have attached a hydraulic graph sheet detailed per the information provided. The approach that I used is time tested by a prominent insurance company and is different from yours. Read the notations and be aware of the scale on the right side of the graph. While the graph is an approximation, by all indications, your water supply is adequate without a fire pump.
Your account is a light occupancy and my archices indicate the sprinkler flow range and the hose stream requirement in the notations. One thing that I am amazed is the large sprinkler orifice size which has a K=8 telling me that it is a 17/32" orifice diameter. Normally such large orifice would be used in hazardous occupancies such as paint storage areas.