NFPA 13d - combined flow

[Eng32]

I am designing a combined sprinkler system for a one family home. The home is considerably large and has a lot of plumbing fixtures. Are there any regulations of the addition of the domestic demand to the sprinkler demand flow rate? Is it a percentage or would I take the full amount and add them together? My domestic demand is 35 gpm and my sprinkler demand is 39 gpm.

 

[sspeare]

Somebody please correct me if I'm wrong, but here goes ......

Re: NFPA 13D (2007); and Article P2904 in the International Residential Code (2009).

In the above-referenced Standard & Code, I have never seen a required GPM allowance for domestic demand, for a single family dwelling. NFPA 13D does require the following:

"In common water supply connections serving more than one dwelling unit, 5 GPM shall be added to the sprinkler system demand to determine the size of the common piping and the size of the total water supply requirements where no provision is made to prevent flow into the domestic water system upon the operation of a sprinkler."

You only have one dwelling unit, so you don't care about the 5 GPM addition. But, I want to draw your attention to the phrase "...... provision is made to prevent flow into the domestic water system upon the operation of a sprinkler."

If you're worried about the simultaneous maximum demand of domestic and sprinkler, you might consider an automatic domestic cut-off valve. I assume you have only a single, combined water supply into the dwelling.

The domestic cut-off valve(check Tyco web site) works hydraulically to stop the domestic flow when there is sprinkler flow. No electric, just hydraulics.

Hope this helps.

 

[wafflefryer]

Don't worry about the provision to shut off the supply to the domestic line.

The automatic shut-off device is only beneficial in dwellings that share the same underground supply. If you have something that shuts off the domestic supply, then you don't need to include the extra 5gpm.

For single dwelling units, don't add anything. There isn't really any added benefit to the life safety system. If the primary purpose of a 13D system is to save lives in the event of the fire, adding domestic flow doesn't make sense.

For instance, pretend the resident is awake and is producing a high domestic demand. If a fire breaks out, the chances that the resident will escape are very high because they are already awake.

Likewise, pretend the resident is asleep and is not producing any domestic demand. If a fire breaks out, the chances that there is any domestic demand is very low (unless they want to take a shower before fleeing the house)

The reason it makes good sense in a duplex that shares the same supply line is because one resident could easily be producing a domestic demand when the person in the other dwelling is asleep.

I hope this was helpful.