Recently we had a 3 building 4 story lightweight wood trussed constructed 55 + complex built with combination sprinkler/standpipe. Currently an old foundry turned furniture warehouse building constructed of heavy timber with masonary being converted into luxury apartments with combination sprinkler/standpipe.
Question, what are your opinions, experiences with the combination?

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If the systems are installed and tested per NFPA standards they will be helpful in containing a fire until you arrive. Proper training on the use of the systems by your company and surrounding mutual aid companies will also be beneficial.
Well they tell us that up to six heads can be off and the standpipe will give 150gpm. If you add your backup line then you need a flow of 300gpm. How do you verify how many heads are off. The condo units are 1800sq ft and have 21 heads in each. We are very leary of using the standpipes. So we have decided not to use the standpipes and will provide our own water source. I know NFPA 13 says that a multi-occupancy, multi floor building 4 stories or less can have these type of systems. However, the NFPA does not consider that the builders build these buildings to be long. These buildings are t-shaped and are roughly 315' by 260'. And did I mention that access is limited. Adding to the situation is how the individual condo units are numbered. They are numbered consequitively. The individual units have 3 hardwired smoke detectors not tied into the main fire alarm system. The sprinkler system is zoned so the water flow alarm generated will only give us so much info. I have spent a ton of hours trying to pre-plan the complexes.
I recently completed a fire inspector class. The way it was explained to me (I think) is that the system is designed to flow the 6 heads or whatever is on the plate based off the city water pressure. Anything additional is gravy. However if there is a FDC you can run the system at 150 PSI with very little concern since this is what it should be hydro tested at. The bigger issue is the size, type, and age of the pipe. I would have the pipe inspected in accordance with NFPA 13 and have the system flushed if needed. In addition depending on the codes adopted by your jurisdiction you could require a pressure gauge at each of the standpipe connections. This would allow you to better calculate what you are actually flowing at the tip. In addition that 150 GPM sounds like it is a 1 3/4 line I would use a 2 1/2 since this is really a commercial structure with residential loading. Just my two cents. Be safe and good luck!!
Ok, I assume with the 2.5" you will flow 200 to 250 gpm. If you add the back up line equal or greater, lets say another 2.5" now your flow would be 400 to 500 gpm. Exceeds the 150 flow. The piping in this complex is new. The trunk lines and standpipes are black iron. The heads come off plastic pipe. According to the plastic pipe manufacture maximum pressure 170psi. I have not been able to get answered if that max 170 includes the street pressure or if the 170 is the max we supplement. Using 2.5" would reduce our pressure added roughly 50psi or less pending the line distance. To be honest using a 2.5" line makes me even more leary of using the standpipes. As for our code enforcement, it lacks teeth. This complex was built after the town fired its BCO and contracted a third party to handle inspections. Further more politics had a play. This complex has one way in and out, with one emergency entrance. The secondary emergency entrance was deleted in order to make three neighboring houses happy. The only hydrant in the complex has limited access and maybe possibly under sized. We are looking into that. Its a tough nut to go back and make changes now that the complex is built. At the beginning my departments input was requested, and we gave it, but in the end it was ignored.
NFPA 13 hydrostatic testing of new sprinkler systems requires 200psi for a period of two hours. As well as annual inspections of systems. Local jurisdiction can mandate the inspections be done more frequently.
IF, the sprinkler system is installed to code.

IF, the sprinklers work as they are supposed to,

Would it really be necessary to be flowing that high of volume to put out the little fire which would be left? Realizing that we don't have many sprinkled buildings in my district, what I have observed, is with proper operation, the majority of the fire would be extinguished prior to our arrival. Common sense also tells me that if the dwelling had the common residential fire load, the compelling reason for utilizing higher volume and bigger hoses would either be an inoperative system, or some type of accelerant would have likely been used.
Granted, but remember sprinklers purpose are not to extinguish but to allow time for occupants to escape. The building I am referring to above is lightwight wood truss constructed. In principle we should be dealing with a mop up.
OK, but the flow testing is done at test head. The orange pvc piping is not tested during the hydro, plus maufacture states max pressure of 170.
Let me ask this has anyone used this type of system? How did it go?
Are pressure reducers installed between the black iron and pvc piping?
Sorry if I mislead everyone. The buildings have three stair towers each, each exiting to the exterior. The one way in and out of the complex is a driveway. There is one main drive and a secondary entrance with a break away chain.
I talked with code enforcement about number 2. They have no beef with the hardwired detectors not being tied into the main F/A. The theory is there won't be as many culinary mishap calls.
Are you sure on that? All systems I ever installed have been tested to 200lbs psi. for a period of two hours, including the "orange" pipe. All piping gets hydrostatically tested.

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