Deciding Not to Design the Fire Sprinkler System Ourselves

Fri, Feb 22, 2019

As you know, we need a residential fire sprinkler system at our place. We are planning to design and install it ourselves. A basic system, that can run off the main water supply, is fairly easy to design and implement.

I called our water management company today to see what kind of flow we can expect from the well, and at what pressure. I was told they do not oversee the water pressure, and have no record of it. I would have to go look at the pump description in person. As for that water flow, our well can generate 12 gallons per minute (gpm). I was hoping this was at least 40, if not closer to 100 gpm.

At 12 gpm (remember this is a shared well, with three other lots, so our expected flow is only 25% of this), we are going to need to have our own reservoir inside the garage. We have to have enough water to sustain our two most demanding sprinklers for at least 10 minutes. Typically this means having about 300-500 gallons of water available. Once a reservoir is in the garage, there must be a pump to pressurize the system, and we must have systems in place to ensure there is no backflow from the reservoir back to the well-house. In short, the design just became a lot more complicated!

My next call was with the Fire Marshal. I wanted to get some advice on a few clauses of NFPA 13D and go over the permit approval process. After going through a hectic permit process for the build permit, I figured it was worth spending a few minutes understanding his expectations.

Right away he advised that we that we have a professional design the system for us. He even went onto say it was required. When I prodded, he clarified that the county does not require a professional to design residential fire sprinkler systems, but that he highly encouraged it. He explained there were a number of things to consider even outside of what was written in the code, and that was fair.

For example, one thing he mentioned was for a multi-purpose system, there is a maximum length for the pipe that comes off the main pipe to the sprinkler. If this pipe is long enough, water will not circulate, and that uncirculating water will eventually grow bacteria and contaminate the whole system. Not a good situation if you’re drinking from these lines.

This was actually something I had already read, but he made a good point, and it’s one that concerns me for this whole project: you don’t know what you don’t know. Our constant blind spot is the questions we don’t even know to be asking. There is no real silver bullet to address this. We just try to take things slow, research as much as we can, and ask as many questions as we can. That’s why I am on this call with the Fire Marshal in the first place!

He suggested that if we really want to do things ourselves, we should at least have a professional review the plans. I haven’t checked yet, but if we plan to get any kind of credit from our insurance company for having fire sprinklers in the home, they likely need to be designed by a professional. I was warming up to the idea.

Given that the system was no longer going to be very simple (we need a reservoir and pump), I have solicited bids from a few firms in the area. I should get quotes next week. Many are stating that their insurance requires them to do the installation too. That may be something we are open to as well. I am sure it sounds like I am flip flopping, in terms of designing and installing it ourselves, but the other recent news is that we have to have mechanical, plumbing and the fire sprinkler system installed and approved before a framing inspection can be scheduled. We plan to do the plumbing ourselves, so we will have our hands full already.

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