Sprinkler riser size 1

[JoeWill123]

Why would an A&E desighn a sprinkler riser in such a way that the existing water main to tape into is 6 inch, but the A&E is desighning an 8 inch on top of the 6 inch pipe as it enters the facility ?

Is it normal to go from a 6 inch supply line to a 8 inch riser?

If so why?

Joe G. Willett
Jacksonville, AR

 

[cdafd]

not normal. If they can hydraulicly prove it I do not think it is against the code.

I questioned one awhile back going from 2 1/2 to three inside the building and they proved it with calcs.
waht does the six inch tap into in the street or down the line???

What is the major type of business in the building office, manufacture, ??????

any fire pump involved???

one story,2,3 ???

 

[TravisMack]

likely, for whatever reason, they were only able to install a 6" underground, but needed 8" riser and bulk main to make the system work. I have done some pretty strange things with sizes when doing a retrofit and dealing with existing pipe sizes.

Just check the calcs, and if it works, you are good to go.

 

[JoeWill123]

Single story, and they are still working the numbers, saying they may have to have a pump now, its a commercial cafeteria building, assembly occupancy.

Joe G. Willett
Jacksonville, AR

 

[TravisMack]

If they need 8", it would make more sense to make the tap on the existing fire line and then increase to 8" to run that into the building.

Again, there is no reason why you install piping that gets larger as it is farther from the supply. It is not the norm, but not unheard of.

Good luck!

 

[JoeWill123]

ok, thank you.......I just did not know if this was common or out of ordinary, I assume it helps to get the hydraulic numbers and calcs within code.

Joe G. Willett
Jacksonville, AR

 

[SprinklerDesigner2]

We used to do this sort of thing constantly in Columbus, Ohio due to what you may consider to be excessive tapping fees.

For those of you who live in the hinterlands and think I am kidding.

http://utilities.columbus.gov/Water/PDFs/2007ServiceconnectionCharges.pdf

Let's compare the cost between a 6" and 8" tapping fee.

A 6" fire sprinkler tap will cost the cost of the tap plus 25% plus the $7,999.00 for the FMCT meter PLUS the capacity charge of $44,835.00. (Assuming the tap will be for domestic water as well).

Total tapping fee, and i have done plenty of them, will run right out $55,000.00 for a 6" tap.

An 8" tap will run cost plus 25%, an additional $9,860.00 for the FMCT meter and a capacity charge of an additional $71,735.00. Total 8" tapping fee will run a minimum of $85,000.00.

It gets much worse outside the city limits in the "contract" areas. In contract areas the capacity charge is doubled resulting in plenty of 8" tapping fees in the $150,000.00 range.

A designer will find himself doing all sorts of strange things, whatever it takes, to get the smallest tap he needs.

 

[JoeWill123]

thanks, I'm not a mechanical PE so I do not know all the ins and outs of hydro calcs, but I suppose they just need to go to a larger pipe size to get the required GPM and pressure at each sprinkler head and to be sure they can certify the system in within code.

Joe G. Willett
Jacksonville, AR

 

[NCDesign]

SprinklerDesigner2 you are not alone. I have seen it done in my neck of the woods on both fire lines and domestic water service. Anything to get the incoming line just one size smaller.

 

[SprinklerDesigner2]

I don't see anything that would prohibit a 4" tap, a 4" backflow preventor, a 6"x4" reducer, used as an "increaser" directly downstream the backflow preventor with an 8"x6" reducer, again used as an "increaser" at the base of a riser with 8" main if so required assuming the system is hydraulically calculated. When is the last time you designed a pipe schedule system?

From NFPA #13 2002 Edition

15.1.3 Size of Fire Mains.
15.1.3.1 No pipe smaller than 6 in. (152.4 mm) in diameter shall be installed as a private service main.
15.1.3.2 For mains that do not supply hydrants, sizes smaller than 6 in. (152.4 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 shall have a main at least as large as the system riser.
15.1.4 Underground Supply Pipe. For pipe schedule systems, the underground supply pipe shall be at least as large as the system riser.

As a side note, in Columbus's defence, the capacity and tap fees are outrageous but anywhere you go you always have a great water supply. Most static pressures run between 65 and 75 psi and we always had at least 2,000 gpm available at 20 psi. 24" and 30" mains are not unusual at all but woe be to the contractor that "guessed" or overlooked the tapping fee.

 

[SprinklerDesigner2]

NCDesign (Mechanical)
27 Apr 07 17:17
"SprinklerDesigner2 you are not alone. I have seen it done in my neck of the woods on both fire lines and domestic water service. Anything to get the incoming line just one size smaller."

That surprises me. Charlotte area?

 

[NCDesign]

Raleigh/Durham

 

[JoeWill123]

Is there a simple formula or website for the calcs?

It looks to me that in my case that NFPA 13, 15.1.3.2 will apply; I would liek to run some rough numbers to see if what the A&E gives me is close.

Joe G. Willett
Jacksonville, AR

 

[SprinklerDesigner2]

Joe, what size and type main are they using?

By type I mean is it cement lined ductile iron, C-900 DR-18 or what?

What is the length and number and types of shut-off valves, elbows or tees (in the case of tee's we only need those that change direction... flow throught he tee is not counted as a tee.

Is there a pit with a backflow device? If so what size, make and model?

What is the results of the flow test on the city water main? Looking for static pressure, residual pressure and rate of flow.

Is this "hill country"? If the distance between the test hydrant butt and flange and spigot is but a couple feet it really doesn't matter much for our purposes but it certainly does if the flange and spigot is 30' above, or below, the test hydrant.

Since the size is less then 6" I will assume there aren't any private hydrants.

Answer these questions and I can provide answers I'll post.

 

[JoeWill123]

Sprinklerdesighner,

I'll do my best to give you the numbers you can use to work with, hopefully it will be enough.

1. Size and type of main: they will tap into a 6 inch main, the main is schedule 40 PVC (plastic pipe), the main system is a looped type.

2.The facility is a dinning hall, approx 140 feet by 140 feet, single story, type IIB contruction, approx 19,132 sq ft.

3. test flow data: water supply, static-42 PSI, residual pressure- 36, residual flow- 920
Water Demand: elevation- 6.063, system flow-442.642, dystem pressure- 28.828, Hose-500, system demand- 942.642, safety margin-6.896
area is relatively flat

4. there will be a backflow device-I do not have the make and model with me, but I can get if its a must, but no pit, (if I understand the term of pit, no elevation issue)

5. there will be at least a PIV shut off valve, a shut off before and after the back flow preventer, not sure of others needed, elbows and Tees...I cant find the srpinkler drawing, I think I can count them from it.

I do not know if I have given you enough to work, thanks again...and pleae let me know if I need to give you more info.

4.

Joe G. Willett
Jacksonville, AR

 

[SprinklerDesigner2]

Joe, I love this sort of thing.

Nice little utility for solving head loss.

http://www.engineeringtoolbox.com/hazen-williams-water-d_797.html

More then likely the pipe is c-900 DR-18 which can be found here

http://www.vtpipe.com/Products/AWWA_C900/awwa_c900.html

PDF file of same

http://www.vtpipe.com/C900.pdf

6" Class 150 has in inside diameter of 6.134".

The design coefficient (we call this C-Value) is 150.

Assume a flow of 920 gpm just to make things easy.

Your input should look like this

http://img240.imageshack.us/img240/5043/sample1qh9.jpg

When you calculate the answer pops up like this

http://img475.imageshack.us/img475/6990/sample2vg9.jpg

At 920 gpm the head loss will be 1.9 psi per 100 feet.

Doing the same thing for 600 gpm we determine the loss to be .90 psi per 100 feet..

Assuming there's not any fire hydrants downstream the city tap we will not have to add the hose stream demand until we get to the city tap. This makes a huge difference as all we will be needing is somewhere around 250 to 300 gpm for sprinkler. Let's figure worst case at 300 gpm.

At 300 gpm our head loss is .20 psi per 100 feet which is pratically negligable.

At 300 gpm the friction loss is .002 or just 2.0 psi per thousand feet.

What we need to do now is figure the total equivalent feet and since I didn't see the actual figures I will make some assumptions and you can follow it through yourself.

Count up the linear feet of pipe from the point of city connection to the flange and spigot piece. Let's assume it's 450 feet.

Now count the total equivalent feet for fittings using this table

http://img358.imageshack.us/img358/2245/ref2km0.jpg

Let's say we have two 6" tees, a gate valve and four elbows. One of these tees is the actual tapping sleeve.

From the table Joe, I love this sort of thing.

Nice little utility for solving head loss.

http://www.engineeringtoolbox.com/hazen-williams-water-d_797.html

More then likely the pipe is c-900 DR-18 which can be found here

http://www.vtpipe.com/Products/AWWA_C900/awwa_c900.html

PDF file of same

http://www.vtpipe.com/C900.pdf

6" Class 150 has in inside diameter of 6.134".

The design coefficient (we call this C-Value) is 150.

Assume a flow of 920 gpm just to make things easy.

Your input should look like this

http://img240.imageshack.us/img240/5043/sample1qh9.jpg

When you calculate the answer pops up like this

http://img475.imageshack.us/img475/6990/sample2vg9.jpg

At 920 gpm the head loss will be 1.9 psi per 100 feet.

Doing the same thing for 600 gpm we determine the loss to be .90 psi per 100 feet..

Assuming there's not any fire hydrants downstream the city tap we will not have to add the hose stream demand until we get to the city tap. This makes a huge difference as all we will be needing is somewhere around 250 to 300 gpm for sprinkler. Let's figure worst case at 300 gpm.

At 300 gpm our head loss is .20 psi per 100 feet which is pratically negligable.

At 300 gpm the friction loss is .002 or just 2.0 psi per thousand feet.

What we need to do now is figure the total equivalent feet and since I didn't see the actual figures I will make some assumptions and you can follow it through yourself.

Count up the linear feet of pipe from the point of city connection to the flange and spigot piece. Let's assume it's 450 feet.

For purposes of example we will assume you have one tee, one gate valve and four elbows.

Now count the total equivalent feet for fittings using this table

http://img358.imageshack.us/img358/2245/ref2km0.jpg

A 6" tee is 30', each elbow (being underground these are considered long turn elbows) is 9' and the gate valve is 3' for a total equivalent fitting length of 69' which, since we are using a C-Value of 150, must be multiplied by a factor of 1.51 and our actual equivalent length is 104'.

104' of fittings plus 450 feet of pipe gives us a total equivalent length of 554'.

Flowing 300 gpm our total head loss will be just (554*.002) = 1.1 psi. This is very little loss.

At 600 gpm our total head loss would be (554 * .009) = 5.0 psi.

Word of caution that has bitten me in the ass before. Be very careful when assigning equivalent lengths to tapping sleeves; while shaped like a tee they are anything but.

Typically the "coupon" from a 6" tap is going to be around 5" and it's going to be a sharp radius turn. To be on the safe side I would count the equivalent fitting length of the tee at 200 feet instead of the 30' shown on the chart. In other words the total equivalent feet I would use would be 811'. At 811' the loss at 300 gpm is 1.6 psi and 7.3 psi for 600 gpm.

This might be useful.

http://img252.imageshack.us/img252/8423/ref1ym5.jpg

Let me post this and I will do a followup. (And double check my math... it's the end of the day, my back hurts and I don't feel like double checking myself. If it were my job I would check it three times but....

 

[SprinklerDesigner2]

Joe,

Is this a military dining facility? The ones I've been involved with, usually have larger areas of application. I seem to remember a denisty of .15 gpm over 3,000 sq. ft. in which case your total sprinkler demand will be around 500 to 550 gpm to which we have to add 250 for hose.

I also seem to remember the corp of engineers always required 500 gpm hose for Ordinary Hazard Occupancies.

I graphed the water supply

http://img440.imageshack.us/img440/6175/graphke8.jpg

and we are going to have around 39 psi available at the street while flowing 600 gpm.

Head loss through backflow preventors.

Is this a double check or RPZ?

Most contractor's use Ames.

http://amesfirewater.com/products/p_colt.htm

For the colt 200

http://amesfirewater.com/pdf/colt2-3j.pdf

the head loss is going to be around 2.1 psi at 600 gpm for a 6" valve.

If it's an RPZ

http://amesfirewater.com/pdf/colt4-5f.pdf

the loss is going to be around 7.0 psi.

Assuming the sprinkler system is wet pipe, that the building is a single story with a ceiling not exceeding 12 to 14' feet I am pretty sure an adequate system could be designed around the given water supply. Now you won't be looking for a 20 psi safety factor or anything like that but it is defintely doable in my mind unless something wierd is going on.

BTW the size of the buidling makes no difference on sprinkler water demand.

The density for an Ordinary Hazard Group I Occupancy is .15 over 1,500 gpm with 250 gpm hose for a theorhetical minimum demand of 475 gpm. I say theorhetical because in actuality your sprinkler demand will be around 300 gpm.. just the way the calcs work.

In a building covering 1,500 sq. ft. your total demand minimum demand will be 475 gpm. ((.15*1500)+250)=475

In a building covering 50,000 sq. ft. your total demand minimum demand will still be 475 gpm. ((.15*1500)+250)=475

 

[JoeWill123]

yes it is a military dining facility; ordinary hazard group .15/3000 ft with hose demand of 500GPM, these include small storage and dinning areas. Ordinary hazard group 2 areas, .2/3000 ft with hose demand of 500 GPM. These areas include the kitchen cooking and prep areas.

Also just as a side nore: flex tubing is prohibitied for this project.

Joe G. Willett
Jacksonville, AR

 

[JoeWill123]

Also.....it will be a wet pipe system, except in the walk-in freezers will be dry pipe of course.

Joe G. Willett
Jacksonville, AR

 

[SprinklerDesigner2]

The freezers won't be dry pipe they'll be dry pendent heads coming off the wet system.

http://www.vikinggroupinc.com/databook/sprinklers/dry/qrstcov/031793.pdf

Normally, per NFPA #13, the dining area would be light hazard with the kitchens Ordinary Hazard Group I but then this is a military job so.....

Are the specs Ordinary Hazard Group I for the dining area with the kitchen/service areas designated an Ordinary Hazard Group II?

Using Ordinary Hazard Group II with 500 gpm hose is a lot of water but I believe doable.

For sprinklers you will need somewhere around 700 which is going to result in a total demand of 1,200 gpm. This is a lot of water for a "Dining Facility".

Pf at 700 gpm is .0026 psi/ft. Assuming 500' total equivalent length, and assuming hydrants are not fed from the 6" service line, the loss is only going to be 1.3 psi. Not terrible.

At 1,100 you are going to have around 34 psi available at the street, deduct the 1.3 psi and 3.5 psi from the back flow preventer and you are going to have around 29 psi at the base of the riser downstream the back flow preventer.

Assume 120 sq. ft. per sprinkler using a 17/32 head will require an end head pressure of 9.0 psi to deliver 24.0 gpm.

Let's assume the highest ceiling is 14'. Elevation will result in a 6.0 psi loss.

End head pressure and elevation requires 15.0 psi which leaves 14 psi for friction loss through overhead pipe.

If design is allowed to "go to the line" this is very doable. The pipe is going to be somewhat big but not HUGE.

If a 5.0 psi "safety factor" is required it is still doable the pipe will just have to get bigger.

Using HASS I just did a quick grid.

140' x 140' building, 10' between lines, 12' between heads with a ceiling height of 14 feet and come up with a total demand of 608.2 gpm @ an estimated pressure at the base of the riser of 24.1 psi. With 29 psi available you got your 5.0 psi safety factor. You can tie the mains together, loss through lines is 3.6 psi, and gain another couple psi but while theoretically possible it's going to be really hard to come up with a 10 psi safety factor.

The grid I figured had 6" mains with 2" lines and the sprinkler contractor, if he didn't figure the job correctly, is not going to be liking this.

Flex heads wouldn't be used on this job even if allowed. The equivalent length to a Viking flex head is 33' of 1" pipe which, flowing 24 gpm, would be a deal breaker on this water supply.

So, if no safety factor is required the job is definitely doable without a fire pump. With a 5.0 psi safety factor I feel the job would still be doable but tough. If a 10 psi safety factor is required then I don't know without actually designing it. I think it *could* be done but the pipe size/arrangement will be getting ridiculous.