Is Domestic Tap Allowed from an NFPA 13 Riser?

4/4/2023

We have an NFPA 13 commercial project.

Do you allow a domestic water tap coming from an NFPA 13 fire sprinkler riser?

If it is allowed, what provisions should I be looking for when reviewing a layout with this arrangement?

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16 Comments

Anthony

4/4/2023 07:03:55 am

No, this would lead to cross contamination issues. IE gross sprinkler water and cutting oil in the water supply. This 100% should NOT NOT NOT be done to an existing system.

You can use a combination incoming service line in some municipalities then split at the flange to a tee one for domestic and one for fire water. But both connections will require a backflow assembly. This is so that the local municipality can cut domestic water off from the building for non payment of water bills and not disrupt life safety. in these cases a DCDA will usually be required.

Jesse

4/4/2023 08:06:09 am

It depends. I've seen numerous times where the tap to domestic is upstream of the riser backflow preventer device. This isn't uncommon at all, and not just on 13R system but 13 as well.

If you're talking about a domestic tap downstream of the check valve and backflow, no way.

Brad K

4/4/2023 08:22:19 am

As Jesse said, we see it often upstream of the backflow. It needs to be approved by code officials and the sticking point is this needs to be a metered supply from the municipality. Lots of fire lines are not required to be metered.

Sean link

4/4/2023 08:06:30 am

If the domestic tap is before the fire sprinkler backflow it would be considered a combination service and it a common method to ensure the fire sprinkler line is not a dead end.

Alex

4/4/2023 10:29:42 am

Sean covered it. If its before the DCVA, its a combined service. downstream from the check, you are now drinking lovely sprinkler water!

Glenn Berger

4/4/2023 08:08:08 am

Domestic connections to the Fire Service is not permitted. Depending on the locality, Industrial connections to the Fire Service may be permitted.

Dan Wilder

4/4/2023 08:23:14 am

I've seen it on existing buildings however the potable piping configuration was specific to Potable piping types (Ductile iron above ground) but we had to place (or add) a reduced pressure backflow prior to changing to standard steel piping to keep the non-potable separated from the potable.

Do it all the time in 13D (copper and CPVC), 13R is less but still available (depending on incoming line size and type).

James Evans

4/4/2023 08:24:24 am

There is such a monster as a circulating fire sprinkler system. You will usually find them in dwellings and piped with PEX. These systems combine all cold domestic and fire water services into one system. It is unusual but can be done.

Josh

4/4/2023 08:33:41 am

Some of the AHJs and utilities I've worked with throughout the country have required the domestic tap come off the underground fire main into a vault where the backflow and meter is.

100% of the time, I go for fire line to be "sacred." Nothing should touch my fire line in other words.

anon

4/4/2023 08:55:33 am

Should domestic demand be added? Why or why not

Josh

4/4/2023 09:00:41 am

I could be wrong on this, but I would think if you tap off your fire main upstream for a domestic line, you would need to subtract the demand of the domestic throughout the building from your available pressure and flow. Unlike us, who hope to never have water start moving through our pipes, the domestic people are going to be hitting peak demand times and days. Not being prepared for that if a sprinkler sets off in your most demanding area and you learn you don't have enough pressure to sprinkler the building would be a bad day.

Chad

4/4/2023 12:04:31 pm

For a 13D yes, its 5 GPM, flat rate.

Casey Milhorn

4/4/2023 09:03:59 am

As others have touched on, it depends on where the tap occurs. At base of riser, before a backflow preventer? After the fire protection backflow, flow switch, etc?

Two main things to consider:

#1 - Is the arrangement you are suggesting allowed by the applicable water department?

#2 - Does the arrangement have inherit practical issues (basically is it even a good idea).

So I would first explore #2 to see if it's even worth the time to ask the water department. If you are talking about domestic coming off AFTER the fire protection backflow, after isolation valve, after flow switch, and/or subject to being energized the the FDC, then stop right there, it's a bad idea and isn't going to fly.

If you are exploring coming off at the base of the riser and assuming you don't have an outside FDC, PIV, or backflow in the underground line, then it might work. Only then would I ask the local water department if they allow this arrangement. But it's probably a long shot, because most water departments are not going to allow their domestic meter inside the building. If you have a combo domestic/fire meter outside the building, then come into building, split fire and domestic, install 2 separate backflow preventers (RPDCVA for domestic and DCVA or RPDCVA for fire) then it might work. BUT I will say, I have seen combo lines with one RPDCVA outside and then the water dept doesn't care if the building occupants are drinking stagnant sprinkler water. If I run into this, I at least add a single check valve for my own conscience.

Todd E Wyatt

4/4/2023 09:11:22 am

2021 NFPA 13 references “DOMESTIC” per the following :

A.5.1.3
...100 mm) pipe is used for the combined DOMESTIC /fire sprinkler systems and the DOMESTIC demand is considerable, then ...

B.1
Figure B.‍1 shows acceptable methods for interconnection of the fire protection and DOMESTIC water supply. Permitted Arrangements Between Fire Protection Water Supply and DOMESTIC Water Supply.

16.11.9 Alarm Device Drains.
Drains from alarm devices shall be arranged so that there will be no overflowing at the alarm apparatus, at DOMESTIC connections, or elsewhere with the sprinkler drains wide open and under system pressure.

A.19.1.5.2
...Where a tank is used for both DOMESTIC/process water and fire protection, the entire duration demand of ...

A.20.15.2.1
...Where a tank is used for both DOMESTIC/process water and fire protection, the entire duration demand of ...

A.5.2.2
...In special situations where the DOMESTIC water demand could significantly reduce the sprinkler water supply, an ...

See REFERENCES below for the complete reference.

Todd E Wyatt

4/4/2023 09:11:51 am

REFERENCES

Chapter 5 Water Supplies
5.1.3 * Size of Fire Mains.
A.5.1.3
For typical combined DOMESTIC/fire sprinkler demands, systems with 4 in. (100 mm) pipe or larger typically do not need to include the DOMESTIC demand in the calculations because it is such a small fraction of the total flow that it does not make a significant difference in the results. But for situations where 4 in. (100 mm) pipe is used for the combined DOMESTIC/fire sprinkler systems and the DOMESTIC demand is considerable, then the DOMESTIC demand should be included in the calculations. Generally, pipe that is 6 in. (150 mm) or larger can carry combined DOMESTIC/fire protection demand without any consideration for DOMESTIC demand being necessary.

Annex B — Miscellaneous Topics
This annex is not a part of the requirements of this NFPA document but is included for informational purposes only.
B.1
Figure B.‍1 shows acceptable methods for interconnection of the fire protection and DOMESTIC water supply.
ENHANCED CONTENT
Automatic fire sprinkler systems can be supplied from a single source or a combination of sources such as a municipal water supply, elevated gravity tanks, at-grade tanks or reservoirs, pressure tanks, rivers, lakes, and ground well water.
In theory, a single water supply would seem to be all that is necessary for satisfactory protection. To rely on a single source to supply the entire system, however, can pose problems. For example, a single supply might be temporarily out of service, it might be disabled at the time of a fire or before a fire is completely extinguished, or its pressure or capacity might be below normal during an emergency. Therefore, a secondary supply is recommended, depending on the strength and reliability of the primary supply; the value and importance of the property; the area, height, and construction of the building; the use or occupancy; and the outside exposures.
The following are some of the most common methods for supplying water to automatic sprinkler systems:
1. Waterworks systems
2. Fire pumps
3. Tanks
4. Fire department connections
While those are the most common methods for supplying water, other water supplies can include reservoirs and even natural bodies of water where approved by the authority having jurisdiction. It is important that the designer consider the environmental factors of the less common water supplies so that the system maintains a high level of reliability. Where natural or raw water sources are used, strainers and corrosion-resistant appurtenances might be necessary.
A connection from a reliable public waterworks system of adequate capacity and pressure is the preferred single or primary supply for automatic sprinkler systems. In determining its adequacy, the designer must consider not only the normal capacity and pressure of the system but also its reliability.

Chapter 16 Installation of Piping, Valves, and Appurtenances
16.11 System Attachments.
16.11.9 Alarm Device Drains.
Drains from alarm devices shall be arranged so that there will be no overflowing at the alarm apparatus, at DOMESTIC connections, or elsewhere with the sprinkler drains wide open and under system pressure. (See 16.10.6.)

Chapter 19 Design Approaches
19.1.5 Water Supplies.
19.1.5.1
The minimum water supply shall be available for the minimum duration specified in Chapter 19.
19.1.5.2*
Tanks shall be sized to supply the equipment that they serve.
ENHANCED CONTENT
The usable capacity of a water tank is based on the sprinkler system demand multiplied by the required system discharge duration as specified in Table 19.2.2.1 and Table 19.2.3.1.2 plus hose demand if required (see commentary following A.19.1.5.2). The tanks’ usable capacity is measured between the inlet of the overflow and the level of the vortex plate inside the tank.
A.19.1.5.2
Where tanks serve sprinklers only, they can be sized to provide the duration required for the sprinkler system, ignoring any hose stream demands. Where tanks serve some combination of sprinklers, inside hose stations, outside hose stations, or DOMESTIC/process use, the tank needs to be capable of providing the duration for the equipment that is fed from the tank, but the demands of equipment not connected to the tank can be ignored. Where a tank is used for both DOMESTIC/process water and fire protection, the entire duration demand of the DOMESTIC/process water does not need to be included in the tank if provisions are made to segregate the tank so that adequate fire protection water is always present or if provisions are made to automatically cut off the simultaneous use in the event of fire.
ENHANCED CONTENT
It is not the intent of NFPA 13 to require the addition of inside or outside hose demands where systems are supplied by a tank unless the sprinkler system specifically supplies hose connections inside the building. Under all circumstances, outside hose is not included in determining the size and capacity of a tank.
When tanks se

Todd E Wyatt

4/4/2023 09:13:00 am

REFERENCES continued ...

Chapter 19 Design Approaches
19.1.5 Water Supplies.
19.1.5.1
The minimum water supply shall be available for the minimum duration specified in Chapter 19.
19.1.5.2*
Tanks shall be sized to supply the equipment that they serve.
ENHANCED CONTENT
The usable capacity of a water tank is based on the sprinkler system demand multiplied by the required system discharge duration as specified in Table 19.2.2.1 and Table 19.2.3.1.2 plus hose demand if required (see commentary following A.19.1.5.2). The tanks’ usable capacity is measured between the inlet of the overflow and the level of the vortex plate inside the tank.
A.19.1.5.2
Where tanks serve sprinklers only, they can be sized to provide the duration required for the sprinkler system, ignoring any hose stream demands. Where tanks serve some combination of sprinklers, inside hose stations, outside hose stations, or DOMESTIC/process use, the tank needs to be capable of providing the duration for the equipment that is fed from the tank, but the demands of equipment not connected to the tank can be ignored. Where a tank is used for both DOMESTIC/process water and fire protection, the entire duration demand of the DOMESTIC/process water does not need to be included in the tank if provisions are made to segregate the tank so that adequate fire protection water is always present or if provisions are made to automatically cut off the simultaneous use in the event of fire.
ENHANCED CONTENT
It is not the intent of NFPA 13 to require the addition of inside or outside hose demands where systems are supplied by a tank unless the sprinkler system specifically supplies hose connections inside the building. Under all circumstances, outside hose is not included in determining the size and capacity of a tank.
When tanks serve both DOMESTIC and fire protection demands, the tank must be arranged so that fire protection water is always available regardless of DOMESTIC demand. Exhibit 19.4 is one example of such an arrangement.

Chapter 20 General Requirements for Storage
20.15 Hose Stream Allowance and Water Supply Duration.
20.15.1
Hose stream allowance and water supply duration for Chapters 20 through 25 shall be in accordance with Section 20.15.
20.15.2 Hose Stream Allowance and Water Supply Duration.
20.15.2.1*
Tanks shall be sized to supply the equipment that they serve.
A.20.15.2.1
Where tanks serve sprinklers only, they can be sized to provide the duration required for the sprinkler system, ignoring any hose stream demands. Where tanks serve some combination of sprinklers, inside hose stations, outside hose stations, or DOMESTIC/process use, the tank needs to be capable of providing the duration for the equipment that is fed from the tank, but the demands of equipment not connected to the tank can be ignored. Where a tank is used for both DOMESTIC/process water and fire protection, the entire duration demand of the DOMESTIC/process water does not need to be included in the tank if provisions are made to segregate the tank so that adequate fire protection water is always present or if provisions are made to automatically cut off the simultaneous use in the event of fire.

Is Domestic Tap Allowed from an NFPA 13 Riser?

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