Residential Fire Sprinklers with Radiant PEX Piping
A few questions have been asked over the years about residential fire sprinklers. I will try to keep this one unique. Has anyone contemplated or attempted to create a wet-pipe rated fire system with the tubing they were already going to use for radiant conditioning?
The goal here is a few things:
1) Homeowner’s insurance discounts.
2) The ability to recirculate the standing water in the wet-pipe system to reduce corrosion, bacteria growth, etc.
3) Consolidation of piping to cut down on incremental expense of installing fire system.
(4) I don’t actually care that much about saving the structure in the event of a fire, since it will be an all-electric new house with modern safety features and egress. The water damage that occurs when sprinklers go off scares me more than the fire risk.
All of this is predicated on the fact that I deem the insurance discount to be worth more than the potential water leak risk of the sprinkler system. I have not convinced myself of that yet, but let’s assume for this question the discounts are worth pursuing.
I looked it up and I don’t think PERT is rated for high enough temperatures so that means my Messana panels will have to be a on a different loop. PEX definitely is. I’m not sure about PEX-AL-PEX though in the case of Warmboard. I think this could work if your radiant system has an auto-fill device to replenish the water as it’s being sprayed. I quickly glanced over NFPA 13D and the requirements don’t seem much harder for a shared piping system vs a dedicated one. It does require 3/4″ minimum diameter which is bigger than I would have otherwise used. Any possible problems I’m not seeing?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
I'm biased, because fire sprinklers save lives, an all-electric house doesn't mean there's no risk of fire in your home.
But I'll just throw it out there: if you have regular plumbing in your house (ie: sinks and showers) your risk of water damage from a leak is no different than with your regular residential plumbing system. The days of exposed pendent sprinkler heads (like in industrial warehouse systems) are over. They're all concealed heads in residential, you couldn't set them off physically if you tried.
Ok to your question: a radiant hydronic system is a closed loop system. It wouldn't work for a fire sprinkler system, the auto-fill system wouldn't be able to supply enough water.
Look into Uponor's fire sprinkler system design. It meets your needs of combining systems to reduce materials/labour, as well as keeping water from stagnation. It combines the domestic water with the fire sprinkler system.
You should probably do at least a ¾" water line for your domestic anyway, ½" can run into supply issues with normal domestic use. But you should have the system engineered by uponor anyway which will confirm the waterline size needed.
I mostly plumb with uponor, it's super fast and easy and cheap compared to copper if you minimize your fittings. I enjoy it.
Jamie
Matthew,
Don't the two systems work at very different pressures?
PEX is incredibly cheap. What's the point?
Combining it with my cold water distribution makes sense, which is going to be PEX anyways. And there would be no conflicts with sizing since we’re not talking about hot water delivery times. It would require at least a couple of small changes though:
1) Build the distribution as a loop. For example, the furthest upstairs/attic sprinkler likely wouldn’t have a plumbing fixture near it so unless it is connected to a loop you would have stagnant water at that end of the line.
2) Install a circulation pump on a timer on this loop.
But these are pretty small inconveniences. Now we gotta get the wife onboard with the aesthetics.
One thing you should consider: if you're using your cold water line as a fire sprinkler feed, then you're running POTABLE water past all the sprinkler heads. That means you'll need sprinkler heads rated for use with POTABLE water systems. That might be a problem.
I deal with fire suppression systems frequently at work, since they're pretty much ubiquitous in commercial buildings. I've never seen a system using shared piping though, and they all tap off ahead of the water meter (fire suppression water is free! :D). There are usually requirements for backflow preventers too, which is another thing that MAY be required on residential systems as well, which would also mess up your plans for a combined system.
The easy way to deal with stagnant water in the lines would be to put a test valve at the far end of the suppression piping and just open it once a year to flush the system. That's easy to do, and commonly done with commerical systems.
Bill
Bill,
We're not talking about commercial systems. NFPA 13D has different requirements for fire sprinkler systems in dwellings.
Also, Look at Uponor's aquasafe system. In other words, a system designed to be a combined domestic and fire sprinkler system. Their fittings and heads are NSF rated brass.
Jamie
Mathew,
No need for a recirc pump. You can go with option 1, ie make your the end of the line terminate to a lav or a washing machine, or some other plumbing fixture that you'll use. It's not necessarily a loop (like a hot water loop) but you're saying the concept, and it's essentially easy to do.
Essentially it's a trunk and branch system, where the sprinkler heads tap directly off the trunk line, and there are ½" branche lines that come off the trunk to supply the fixtures. Have 1 or more ½" lines branch after the last sprinkler head.
If you're serious about this, you can probably find an uponor rep to ask if they know of any plumbers in your area that are comfortable with this system. I'm sure you can ask them questions as well.
Jamie
I love Uponor systems, and I agree that fire suppression in residential buildings is important. I've been pushing for years to make this a priority if wood framed structures, but I don't see it as anything up and coming in the code world in the near future, mostly due to cost prohibition and lack of qualified design professionals that are making it an issue. On the other hand, I build with ICF's, and our builds are much more fire resistant in nature, so I guess it's a double edged sword.