I work at a complex that has one 350,000 gallon tower and two other 350,000 gallon tanks. Which goes over 1,000,000 gallons of water on facitlity for fire suppression, for those of you counting. The building I work in is a one story building that covers 1.8 million square feet, and it is simply one of the buildings on campus.
180,000 gallons of water would not be unreasonable for a tank of sprinkler water.
I've never seen a 350,000 gal tower before, but as I posted previously, 180,000 gal is not unreasonable.
The problem you get with high rise buildings is getting enough water pressure to run the actual sprinkler heads.
Agree. But flow is equally as important as pressure.
Most heads will not function at less that about 95 PSI.
This does not conform to my experience. Cite please? A sprinkler head will "function" at almost 0 flow and 0 pressure, i.e. the link will fuze, the glycerine will burst, etc. It just needs adequate flow and pressure to protect the occupancy.
You can buy heads that are low flow, but you'll still need somewhere in the range of 75 PSI to run them, and then you will need more to make up the difference
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Again, I question the 75 psi statement. The rest of the statement sounds like you are saying with "low flow" heads (whatever they are) you have to decrease the sq. ft. coverage/head?? Please explain what you mean.
Each water pipe you hang adds weight.
Of course. But what does this have to do with water flow/pressure/extinguishing capability?
There might be a reservoir in a tower that size, but putting that much water that high in the air creates other problems. You can't dampen for sprinkler water. If you did, and you had a fire, suddenly you are damping for a weight that isn't there.
Good point. Hadn't considered that.
I doubt it is a 180,000 gallon tank. It would be more like 500-1000 every so many stories attached to a pump. The tank would be there in case the pump started.
Possibly, but my experience is that you just take suction from the city underground main (assuming you have a reliable supply there), and then provide a booster pump at regular intervals as you increase elevation
You could get a negative pressure wave through the system unless you have a way to negate it. The tank is the way you do that.
Not sure what you are talking about here exactly.
And that would be at most. There was probably a pump every so many feet that would boost pressure in the system. This is probably the most cost effective way to manage it. You could gravity feed it, but that is a long ways up to pump water in order to gravity feed the system.
Agree. see above.
Actually, if you have a gravity system, you just use a small fill pump to continually make up for any pipe leakage, etc. In a fire situation, once the gravity tank is empty, you are SOL as that little pump is ineffective.
Remember, fire systems are flushed and tested every so often. Why run a huge-ass pump to try to push it all the way up the hill when you can use a medium sized pump to push it halfway?
Actually, the testing on a wet-pipe sprinkler system as far as water usage is concerned is rather small. The two inch drain where the riser enters the building is probably tested monthly for about 30 seconds. The inspector's test connection (which simulates flow from one sprinkler head) is probably tested twice a year.
On large systems, there are sectional valves that can be closed to avert having to drain an entire system.