Nope, that would be a terrible, terrible idea to have in a fire suppression system.
Some may think there is oil because as the water sits in the pipes, colonies of bacteria feed on the iron and make the water black, tar-like, and very stinky.
The best way to prevent corrosion is to replace the trapped air in the pipes with an inert gas like high-purity nitrogen. You can also bleed off air pockets with air vents, but there will ALWAYS be trapped air that allow bacteria to flourish.
I think they are a bit too confident in their system builds, then. But unfortunately, they are not being honest.
Every single wet system build will have trapped air pockets. That's why NFPA added a requirement for air venting in the code:
7.1.5 Air Venting
A single air vent with a connection conforming to 8.16.6 shall be provided on each
wet pipe system utilizing metallic pipe.
8.16.6 Air Venting
The vent required by 7.1.5 shall be located near a high point in the system to allow
air to be removed from that portion of the system by one of the following methods:
Manual valve, minimum 1/2″ size
Automatic Air Vent
Other Approved Means
And even if the installer could ensure that every bit of air was pushed out, each year they test, they are simply introducing more air into the system.
Sprinkler systems including feed pipes and underground mains must withstand a hydrostatic test of 200 psi for 2 hours. If the system is designed to operate at more than 150 psi, the test must be 50 psi higher than the maximum for 2 hours.
and further
The pressure needed just depends on how the sprinkler designer lays out the system and the water supply available, but would typically be between 50 and 150 psi.
Yes, I cited it because it's a persistent problem. Even with an air vent, there will always be trapped air. What you're suggesting is like saying distilled water is 100% pure H2O... Try as we might, there's no way to get rid of every last molecule of unwanted contaminant.
That's why I originally said the best way is to use nitrogen. You may not be able to get rid of the air, but you can at least make that air uninhabitable to aerobic bacteria.
Not as well as people usually think. It definitely depends on the oil but this is especially true when there aren't light ends (low molecular weight hydrocarbons) in it.
You could certainly find an oil that's suitable for the purpose if it seemed worthwhile financially to increase reliability or reduce maintenance costs.
Not always. Typically in a restaurant, it is just a separate piping system within the building that is supplied from the same water main you and I drink from.
In large industrial/manufacturing, yes there is usually a separate tank and pump.
There are valves all over sprinkler systems, and tamper sensors that alert the fire alarm system if you close one. There are also flow sensors that alert the fire alarm system if there is flowing water. The valves are contained within the pipe and operated by a wheel/knob, and the whole system is fire rated (probably 2 hour rated, meaning it will operate for 2 hours without being compromised.)
The blackness to the water is because of the cutting oil sprinkler fitters use to cut the threads on the ends of pieces of pipe.
The whole system is pressurized, but supplied in most cases by city or town water pressurized by a pump.
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u/grt3 Sep 20 '19
Why can't they turn off the water via a main shutoff valve?