Fire Water Storage Tank - Overflow Protection (A requirement?)

[ziptron]

Hi Everyone,

I am aware of a situation where an open to atmosphere Fire Water Storage Tank installed in a mechanical penthouse (not rooftop) of a building overflowed. It overflowed because a float switch failed to close. The overflow went into the mechanical room, flooded it and caused damage to the lower part of the building. The tank had no high level alarm so the owner had no clue that this was about to happen until it did.

I am now on a job site where I see a water storage tank in a similar configuration. Although it has a float switch, it has no high level alarm. I would love to convince the owner to install a high level alarm but I am getting push back. I think it should be done. Is anyone aware of codes/regulations that require high level alarms to be installed?

Drainage of overflow is not a good option as the building is old, tall and the current drain leader would not be able to carry away the entire amount of overflow (if it were to happen). Installing a leader big enough is just not possible.

I reviewed NFPA 22 and I am not seeing anything that specifically requires overflow warning/protection such as a high level alarm. I do see however in NFPA 25 that "How and Low level alarms should be tested semi-annually". I'm getting mixed signals here...

Any guidance would be appreciated, thanks!

 

[PEDARRIN2]

I have designed a few of these and always recommend means of overflow even with the alarm.

Ask the owner which he wants to spend money on.

1. overflow switch and alarm? - likely cost in thousands
2. Repair/replacement of damaged building equipment/contents? - likely cost in tens of thousands to maybe millions.

When he says it never happens, show him the instance where it did.

Is it likely? Probably not.

Is it possible? Definitely.

Document his decision and walk away.

 

[ziptron]

I definitely agree with you. That is what I should do and what every prudent building owner should do (if property damage is at stake). I was just hoping that there was some sort of code/standard that says the same. Sort of surprising that I cannot seem to find one.

 

[cneberly]

I have designed many of these type storage tanks for domestic and fire water service (called Break Tanks). The City of Houston requires these tanks for practically all multi-story buildings. The standard design includes an overflow for all compartments. The tank overflow discharges into an adjacent floor drain or directly outside the building. Also used is a level control system with lo/hi water alarms. Of course when alarm power fails, the overflow piping should protect the building from flooding. Having been involved with some flooding buildings (a flooded bank lobby on Friday morning is a real bummer!) I can sympathize with the owner and highly recommend a responsible design from the engineer.

The attached link should provide more detail information:

http://www.parkusa.com/index.php/products/tap-water/break-tank-system

Chris Eberly, PE

http://www.parkusa.com