Fire sprinkler system, Back flow preventer?

[Paddy]

I'm building an all concrete home but just had to make one last point to make this beast fire proof?

It's not a comercial version, just a 3/4" line running about with 1/2" lines feeding the sprinkler heads. (Comercial systems are designed to have them all go off at the same time, so they feed them with 3"+ line with 20,000 gal storage tanks powered by diesel pumps). Not me, I want to "supress" a fire in the one location it starts.

So one key thing is a back flow preventer. Water gets real nasty siting in the pipes. I did a google and it looks like I need a "double check valve back flow prventer"

Any one do a DIY sprinkler system? and What did you use for back flow prevention?

Patrick T.

 

[Toddao]

In boiler room we have 2 sprinkler heads off the domestic water system . Purchased the house this way , The way I see it they will control anything that starts in that room .

 

[RobertBrown]

I'm building an all concrete home but just had to make one last point to make this beast fire proof?

It's not a comercial version, just a 3/4" line running about with 1/2" lines feeding the sprinkler heads. (Comercial systems are designed to have them all go off at the same time, so they feed them with 3"+ line with 20,000 gal storage tanks powered by diesel pumps). Not me, I want to "supress" a fire in the one location it starts.

So one key thing is a back flow preventer. Water gets real nasty siting in the pipes. I did a google and it looks like I need a "double check valve back flow prventer"

Any one do a DIY sprinkler system? and What did you use for back flow prevention?

Patrick T.

Most residential systems are piped with cpvc Blazemaster.
A BFP is a good idea and depending on how your water is supplied you may have a code that applies. You can get a good 1" double check at your local H.D supply for around 150$.
It's the same one munincipal water supplies require for a tie in on a "city" water supply.
If you have a well and you feel 150$ is a little steep just use 2 3/4" check valves in line.
Be sure to use "Residential" heads spaced and installed in accordance with N.F.P.A. 13 2007. You may be eligible for a discount on your insurance, other wise your homowners could go up as they don't want to pay for water damage.

 

[JB4310]

Standard irrigation back flow preventer, don't know if something like this would work?

Backflow Inspections | Backflow Testing Irrigation Chesterfield County VA

It's big business now, a plumbing company I know just does back flow prevention work now, they even changed their name to reflect it.

JB.

 

[Kays Supply]

If you run your water lines so that you don't have over a 24" dead leg, you won't need a Backflow preventer. Just take the sprinklers off a line running to something else. It might take a little extra pipe. You don't have to use just one pipe. You could tap off different places just keep the dead legs as short as possible.

 

[eepete]

A life safety domestic sprinkler system often uses the sprinkler lines for the cold water. That solves all the stale water problems. The only problem left is dealing with a the plumber who will want to charge you lots of $$s because he's doing something he's never done before. I've help install sprinkler systems in some Habitat for Humanity houses. We ran all the sprinkler pipes in the attic and then left drop downs for the plumber for the cold water. Attic insulation has to be right for any residential sprinkler system.

When I sprinklered my house, I fed the sprinkler system from one end, and at the other end used a 1/4" pipe to feed it back into the cold water. The "Far" end of the house where this tie back happened was in the area of the master bedroom, so there would be guarantied daily use. The tie back meant that water in the sprinkler pipes would always be slowly exchanged. So I have the plumbing in the house "standard", and the sprinkler is a separate system, but the tie in keeps the water from getting stale and a back-flow valve (and the subsequent drop if flow/pressure) is not needed. As for the attic insulation problem, the house is foam insulated so the attic is conditioned space.

I'm on a town water system, so I did not need a tank and booster pump. I did put in a 2" feed to the house (the length was 800 feet).

I also put in a purge valve at the far end so I can run the pipes at maximum flow. I purge it twice a year, all you have to do is run the purge for about a minute. My hope is that this will encourage a little exchange of water with the dead ends in the system.

I have cut out valves at each end with nice signs for the Fire Dept. I suspect these will be handy for me if a head goes off and I need to shut the system down. The valves get exercised annually.

Kays Supply: the 24" dad end figure you quote is interesting. I asked the local inspector about how long a dead end could be (since the sprinkler system had a few places where the head has to branch off of the main line) and he said six feet. so I've got 2 places with a 6' dead end, and a number of places with 2-3 feet. Can't do anything about what I have, but any more information you have on this would be wonderful.

Pete

 

[nybirdman]

All a backflow preventer is :is two check valves with a RELIEF between and ports to test.If the first check leaks it will drip between the two checks..and you know it is time to :change/repair.For residential I like the idea of recirculating the water,keeps the water fresh.I.E. tie it to the regular plumbing system.Most commerical systems are iron pipe(threaded) but for home use copper will work.Are there any codes in your area for residential?
All in all....good idea.Show everyone in the household the shut-off.
40 years in the business.

 

[slowzuki]

Just a note to counter the myth, commercial systems are not designed to go off all at once. They have a heat sensitive bulb in the sprinkler and only operate near the fire, or near the guy who hit it with the forklift lol.

 

[WM75Guy]

It's not a comercial version, just a 3/4" line running about with 1/2" lines feeding the sprinkler heads. (Comercial systems are designed to have them all go off at the same time, so they feed them with 3"+ line with 20,000 gal storage tanks powered by diesel pumps). Not me, I want to "supress" a fire in the one location it starts.

Patrick T.

There are many types of systems. The one you describe is a deluge system used only in special circumstances like aircraft hangers. Commercial sprinkler systems have heat activated heads, they only go off in proximity to the fire just like a residential system. The bigger the fire, the more heads go off. Commercial systems are closed systems, the water feed is separate from domestic use, therefore a backflow preventor is required to keep the nasty stale water out of the public water supply when the pressure drops in the public water supply system. In the past the alarm valve acted as the backflow prevention, however they were not designed to do that, so the backflow preventers were required.

 

[WM75Guy]

The big difference between a residential system and a commercial system is the residential system is for life safety, the commercial is for property protection. Residential systems only cover areas that are normally occupied, such as bedrooms and living spaces. There are not heads in closets or storage areas. They allow the occupants to escape if a fire occurs. They do not have enough coverage (fireflow) to extinguish a fire if it gets beyond the incipient stage.