Anti-freeze vs. Dry sprinkler system 2

[SB63]

Is an anti-freeze fire sprinkler system advantageous over a dry pipe fire sprinkler system? I get the impression that dry pipe is preferred. Is an anti-freeze fire sprinkler system more hassle or more expensive in the long run?

When would anti-freeze fire sprinkler system be optimal? My impression would be very small area or just a couple of rooms.

It appears the only long term cost with dry pipe is maybe replacing the air maintenance device? Thanks

 

[TravisMack]

There used to be wording in NFPA 13 where anti-freeze systems should only be used for areas where the piping volume is less than 40 gallons. However, in the 2002 edition, that restriction was removed.

Anti-freeze systems typically lead to smaller piping as you can take advantage of QR sprinkler reductions (if applicable). You are also not penalized the 30% increase you have in a dry system. Finally, you can use a C-120 for an anti-freeze system vs. a C-100 for dry systems (unless piping is galvanized). That being said, there are concerns that you will likely require a RPZ which will constantly "burp" anti-freeze solution. The solution would need to be checked yearly.

Dry systems have their own problems as well. Unless the system is able to be pitched with no low point drains, you will need to have "drum drip assemblies" installed at each low point. It is MANDATORY to have these drained each year as it is common for them to freeze, break the pipe and trip the valve if they are not drained each year. Also, with a dry system, you have an inherent delay in delivering water to the fire if an event occurs.

The maintenance costs each year are about the same. You still have the inspect the system, trip the valve, drain the drum drips, etc for a dry system. You have to test and add antifreeze solution each year for the antifreeze system. Any time you want to work on an antifreeze system, you have to drain the water to a storage device, then refill with the antifreeze solution when you are done working. If you have a 750 gallon system, you will need a place to store all of those 55 gallon drums while you are working.

Overall, I think each system has its + and -. It is site and project specific as to which you should use.