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Two waterlines serving one sprinkler system

SCBO1

SCBO1

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I have a question in regards to a sprinkler system water service line.

Can TWO 2-inch lines be used to service ONE 3" interior sprinkler system instead of a single 4-inch water service line?

Is there's any IFC codes or other codes that would allow or prohibiting this set-up?

pc1
 
Would say not allowed for many reasons

It would come out of nfpa 13

If even allowed would have to prove it with hydraulic calcs

If serving commercial building I am pretty sure the answer is no.

If serving a hotel, townhouse or similar as in a 13r system than maybe

Is someone proposing or general question??

Not near the book
 
It is being proposed by the building owner for a commercial building, if the sprinkler designer does the calculations and stamps it.

Needing to know if allowed or disallowed by codes.

pc1
 
It is stupid to do

1. will your water utility allow it?

2. what fire sprinkler company is going to try to design with this water suppply?

3. here is from NFPA 13 2010 edition

23.1.2 Capacity. Water supplies shall be capable of providing

the required flow and pressure for the required duration as

specified in Chapter 11, Chapter 12, and Chapter 21.

23.1.3 Size of Fire Mains.

23.1.3.1 Except as provided in 23.1.3.2, no pipe smaller than

6 in. (150 mm) in diameter shall be installed as a private service

main.

23.1.3.2* For mains that do not supply hydrants, sizes smaller

than 6 in. (150 mm) shall be permitted to be used subject to

the following restrictions:

(1) The main supplies only automatic sprinkler systems, open

sprinkler systems, water spray fixed systems, foam systems,

or Class II standpipe systems.

(2) Hydraulic calculations show that the main will supply the

total demand at the appropriate pressure. Systems that

are not hydraulically calculated
 


This seems to be a non-cost effective supply scenario due to additional metering, backflow assemblies etc. if both are not “brought into the building” in a single supply. As CDA mentions the standard NFPA 13, 2013 [24.1.3] will allow supplies less than the minimum 6" or 4” (single main) if hydraulic calculations can prove the proper design and density parameters for the occupancy classification. I would recommend consulting the water supply section of your referenced NFPA 13 for additional guidance. If these are existing duel 2” domestic supplies into the building it would probably be more cost effective during the infrastructure analysis to combine both.
 
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there is question

does your ahj require a meter for each line

does your ahj require a backflow for each line or is it installed inside the building

where will the fire department connection be on the building or in the street

also,"underground pipe" has to be listed for "fire protection use" NFPA 13 10.1.1 2010, not to sure but I do not think that you will find two inch listed for fire protection use.

and minimum rating of 150 psi

and all the other requirements for "underground piping" of Chapter 10 NFPA 13 2010 edition
 
cda,

Yes, PW Department requires a meter on a fire line

Yes back-flow would be required on the 4" or the TWO-2" lines if allowed by code.

FDC on the building, 5-inch Storz

Underground pipe would have to meet the fire protection line requirement. ***Will need to verify that a 2-inch line is listed for fire protection use. Fire Protection Designer will need to provide this on plans.

Will need to verify rating of 150 psi and that it can be provided by TWO lines

pc1
 
retire09 said:
Two 2" lines are equal to 1/2 of a 4".
Click to expand...
pi x R squared = si

Two 2-in pipe = 6.283 si

4-in pipe = 12.566 si (twice amount of area inside pipe)

FWIW above does not include nominal friction loss pipe to wall surface area and assumes no difference in wall thickness between different pipe materials.
 
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I assume the minimum pipe size is dictated to somewhat take into account the effect of future scaling / build up inside the pipe?
 
= & = & =

What if one of the 2 - 2" lines breaks, or is down for a significant time for repairs ?

Is there a Plan B for this scenario ?



= & = & =
 
north star,

I would think that if a 4" line was down we would have an issue.

I would think that if one of the 2-inch lines were down we'd have the same issues, lack of pressure I would assume the sprinklers would not work properly.

We ran the idea by another city water department head and one comment was a 2" meter would cost less to replace than the 4" water meter.

Would't you get better water pressure from the two 2-inch lines vs the one 4" line?

Plan B, install a 4" radio read meter including back-flow and concrete vault.

A 2-inch meter does not require the vault that houses the valves, meter and back-flow devise.
 
& ~ & ~ &



Pcinspector1,

I am not competent enough to provide you an answer regarding the

2 - 2" lines of pressure, versus 1 - 4" line.......As **cda** mentioned,

obtain the flow calcs. and go from there.

If it were me, I would want to look at the actual math calculations

first, before I started any "What If" type scenarios.



& ~ & ~ &
 
Pcinspector1 said:
north star,I would think that if a 4" line was down we would have an issue.

I would think that if one of the 2-inch lines were down we'd have the same issues, lack of pressure I would assume the sprinklers would not work properly.

We ran the idea by another city water department head and one comment was a 2" meter would cost less to replace than the 4" water meter.

Would't you get better water pressure from the two 2-inch lines vs the one 4" line?

Plan B, install a 4" radio read meter including back-flow and concrete vault.

A 2-inch meter does not require the vault that houses the valves, meter and back-flow devise.
Click to expand...
We got away from vaults thank goodness.

We see the backflow inside stacked on the riser. Water utilities puts an electronic transmitter on the bypass, it can be read from outside electronically

We do not have any meter at the tap or part of the underground, just slows down the water

"""Would't you get better water pressure from the two 2-inch lines vs the one 4" line? """. Not an engineer but my guess is NO
 
If this is a full NFPA 13 system I am quite sure the proposal does not meet NFPA 13.
 
cda,

Health clinic, with tenant requiring a sprinkler system from the landlord.

Landlord trying to save $$ A 4" radio read meter comes at a greater cost including the vault.
 
Who supplies and installs the meter

The city or sprinkler contractor ????
 
If the building is required to be sprinkled by whoever, cost of doing business

Will send you a picture of our set up on Monday
 
cda,

4" water meter will be purchased by landlord meeting city requirements and brand and delivered to the site with vault

2" water meter is purchased from the city and supplied by the city with pit

Thanks for the info.
 
Other problemS

Is five feet out they need to transition to normally metal lead in.

So they would have to connect the two lines to the lead in

Or if allowed to take the two pipes into the building have to connect the two lines into the riser
 
Do you have a fire sprinkler contractor you trust??

If so call and run the idea by them and see what they say about the idea
 
If hydraulicly it can be proven it will work you can do it as per NFPA 24 and 13. BUT most likely not, the flow will be about 150 GPM .10/1500 or less if they use quick response sprinkler. What is the static and residual city water pressure, how many feet of 2" main do we have from the building to the city street, do we have any elevation change between the two points. Is it a straight run or do we have many elbows. How old is the pipe if old most likely not 2" anymore because of interior corrosion, what type of pipe copper, steel, cast iron. As you can see many factors to be considered. Make sure you get a sprinkler contractor involved and review the hydraulics calculations line by line that will be the only way to know for sure. If it works you are good, if not we'll nice try, now put in a new properly sized main.
 
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