How Much Water Does a Commercial Sprinkler System Put Out?

6/24/2021 (Permalink)

Ever wonder how much water your commercial sprinkler system can put out?

We can tell you from experience that it is a massive amount of water. When we arrive on-site to provide fire and water damage restoration after the sprinkler system has gone off, we usually have several days of mitigation and drying ahead of us.

In general, this is a good thing. Fire prevention systems are designed to only put out as much water as they have to in order to put out the fire. Contrary to what you see in the movies, your entire sprinkler system does not go off in case of a fire. In most systems, the response is localized to areas where the fire is active, since it is the heat from the fire that bursts the sprinkler bulbs and prompts the water to flow in the first place.

But how do you calculate how much water flows through your sprinkler system per minute? There are two ways to figure it out.

The Easy Way

The simplest way to get this question answered is to just ask your fire prevention company. They’ll be more than happy to explain to you exactly how the system works, how much water it is capable of putting out, and how best to maintain it so that it operates as designed.

Trust us – they’ll be happy that you called. 99% of the time, when someone calls their fire prevention company, it’s because something has gone wrong. You could be in the 1% of people who took an active interest in their system before they needed it.

The Hard Way

If you really want to figure out how much water your system can put out by yourself, then you should be prepared to do a little math.

Your overall flow rate depends on the flow rate of each individual sprinkler, which in turn is affected by things like the dimensions of the sprinkler’s opening, friction within the line and other factors. Each individual sprinkler should have a “discharge coefficient” provided by your fire prevention company that takes all of these factors into account.

Each sprinkler should also have a pressure rating expressed in “pounds per square inch.” Again, this should be simple to find via your fire prevention company.

To come up with a figure for gallons per minute, you multiply the discharge coefficient by the square root of the pressure rating.

Here’s an example. You have 24 sprinkler with a pressure rating of 20 pounds per square inch and a discharge coefficient of 6.1. The square root of 20 is 4.47.

6.1 * 4.47 = 27.26 gallons per minute.

If you multiply 27.26 by 24, you get the flow rate for that entire set of sprinklers: about 654 gallons of water per minute.

Like we said – it’s a lot of water! But if you’re dealing with a fire, you’ll be glad to have every last drop.