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.
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.
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.
This is directly from Harvel's website just to show that I am not pulling your leg.

Maintenance
Maintenance shall be in accordance with the Standard for Inspection, Testing, and Maintenance of Water Based Sprinkler Systems as defined by NFPA 25.

Limitations
CPVC systems are intended for use at a maximum working pressure of 175 psi and ambient temperature of 150F.
CPVC systems shall employ sprinkler heads having a maximum temperature rating of 225F or lower, regardless of type.
CPVC products shall be installed in wet pipe systems only.
Air or compressed gas shall never be used for pressure testing.
CPVC sprinkler systems shall be hydrostatically tested for 2 hours at 200 psi, or 50 psi in excess of the maximum working pressure when the maximum working pressure exceeds 150 psi. Lines shall be slowly filled with water and the air bled from the highest and farthest sprinkler heads before test pressure is applied.
Only Teflon tape or a thread sealant specifically approved for use with Harvel CPVC Fire Sprinkler Products shall be used in making threaded connections.
Where freeze protection is required, only glycerin based anti-freeze solutions shall be used and installed in accordance with NFPA 13. Do not use glycol base anti-freeze solutions or contaminated glycerin solutions.
CPVC is not approved for use in combustible concealed spaces where sprinklers are required to protect these areas as defined by NFPA 13, unless certain specific application sprinklers are installed per their listing. Refer to Harvel’s current Installation Instructions for additional information.
CPVC sprinkler piping may be installed in a plenum space adjacent to, but not over, openings in the ceiling such as open ventilation grills, and require the use of schedule 80 fittings for use on 1-1/2” and larger pipe sizes. Refer to Installation Instructions for additional detail.
Minimum protection when installed “concealed” shall consist of: 3/8” gypsum wallboard or drywall, suspended membrane ceiling panels weighing not less than .35 pounds per square foot, or 1/2” plywood soffits. Minimum protection for NFPA 13R and 13D systems may consist of 1/2” plywood.
Harvel BlazeMaster pipe is Listed for use in exposed applications with certain limitations. When installed without protection, “exposed” pipe is to be installed beneath smooth, flat, horizontal ceiling construction. Exposed categories include: standard coverage and residential pendent and sidewall sprinkler applications, light hazard extended coverage and residential sprinkler pendent and sidewall sprinkler applications, use in unfinished basements with exposed solid wood joists, light hazard upright quick response sprinklers, and system risers (in 13R & 13D occupancies). Refer to Harvel’s installation instructions for specific sprinkler head temperature ratings and spacing requirements. The product must be installed in strict accordance with NFPA 13, 13D, 13R and Harvel’s current CPVC Fire Sprinkler Piping Products Installation Instructions (HFS-3).
Harvel CPVC Fire Sprinkler Products must be installed in accordance with Harvel’s current installation instructions (HFS-3).


Working pressure means the pressure that the system is in service at, which will depend on the incoming water supply and whether or not there is a fire pump installed in the building. I am going to assume that there probably is a pump due to the size of the building.
the system installed here is by Tyco. The system is wet in climate controlled areas. The attics are glycol, in black iron. The heads that protect the balconies, bank drive thru and breeze way are dry. The dry pipes are factory set. They ar 18" long with a one way air valve connected to the interior pvc.
Tyco,Harvel,Blazemaster CPVC pipe is all made to the same specifications. The point I was trying to make is that they should have been tested @ 200lbs for two hours per NFPA standards. If you take a close look at most of the devices used in a fire protection system their specifications show a working pressure of 175psi.
If the system was designed correctly and installed per the drawings you should have adequate pressure at the furthest hose valve even if you are flowing the calculated amount of heads. Especially if there is a pump involved.
Are pressure reducers installed between the black iron and pvc piping?
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.

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