Manual dry standpipe FDC / Why a check valve? 2

[SprinklerDesigner2]

I have a manual dry standpipe, it's the only one I've ever done in my life the reason being most jurisdictions I've worked in never allowed dry manual standipipes, and I just got approved drawings back with a note requiring a 6" check valve with ball drip between the 3-Way FDC & system.

Hey, I got approved drawings so I'm going to argue but what is the reason for the check valve?

BTW I did have a ball drip check at the 6" elbow through wall.

Anyone?

 

[Cidona]

I think it's just for good luck

A couple of reason come to mind though they might not be the reasons it was incorporated into the standard.
a) Allows pressure testing without modifications.
b) Gives control of draining the system once the pumper has stoped pumping.
Intersted to hear other reasons people have.

 

[cdafd]

1.does nfpa 14 requie it?
2. so the water does not come back against the fdc?
3. because I said so?

4. ask for a section reference

 

[RWF7437]

The most probable reason is to prevent a cross connection between the public, potable, water supply and a water source whose quality is possibly contaminated or simply unknown. A sudden drop in pressure on the public side of the connection could allow flow from the building sprinkler system ( which may contain brackish water or antifreeze, back into the drinking water system. Most often, a double check valve would be required to ensure such contamination does NOT occur.

Such a pressure drop is especially likely to occur during a fire when very large demands are placed on the supply.

You didn't say which way the check valve is allowed to flow.

 

[cdafd]

RWF7437

it is dry, the pipe has no water in it and is not connected to a water supply

the fd pumps into it, so for cros contam it would have to flow back through the fire truck pump and back through the hydrant.

 

[Cidona]

With enough head pressure I wouldn't see why that wouldn't happen. I think RWF mentions a good point. I wonder if the water going back through the pumper would have a negative impact on the pump.

 

[RWF7437]

cdafd,
It is perfectly possible for water to flow backward through a pump. I have seen pumps that ran backward for 20 years. They didn't run well but they ran !

Cidona,

Unless the pump itself has a check valve, and the check valve is working, and unless the pump is the only source of pressure, backward flow is possible. Although the water supplier has a duty to provide fire flows, the supplier's principal duty is to protect the public health by preventing contamination of the supply.

Very few, if any, Fire departments pay for water. Very few, if any, pay any attention to contamination or the cost of providing water, or the other uses of water. It is the supplier who bears these responsibilities, and legal liabilities.

Damage to a pump on a fire truck would be the least of the undesirable consequences.

I'm not a fireman, or a sprinkler designer, just an old water system guy.

 

[stookeyfpe]

The check valve is required so if too much crap is in the standpipe, the firefighters can sacrifice a section of hose, cut it with an axe, and return to service.

It's a real problem. Which is why I hate dry standpipes and worse, Class II hose connections.

I spent 36 hours at Parkland Memorial Hospital in Dallas 25 years ago dealing with a heroin addict needle that shoved through my gear dealing with a dry standpipe on a 7 story parking garage. The assignment was a crappy car fire. I would have rather laid a horizontal hose load and hurt my back. I am Hepatitis C free but the testing for the virus was a royal pain in the rear.


We firefighters (OK, I am a former firefigher) are not perfect. As engineers, we are even less intelligent.

A true story.

 

[cdafd]

OK STOP the conspiracy theories and stop beating up on the plan checker.

see item 1 and 3 on above post

take the poor plan checker a doughnut and some glasses so he can see you already gave him what he asked for

Get your NFPA off the shelf dust it off and if you have the 07 check 6.4


6.4* Fire Department Connections.
6.4.1 Shutoff valves shall not be installed between the fire department connection and the system.
6.4.2 A listed check valve shall be installed in each fire department connection and located as near as practicable to the point where it joins the system.

 

[FFP1]

I already have a very good opinion of Stookeyfpe, but I am even more impressed knowing he is a FPE with firefighter experience. My brother is a full time fire fighter (Lieutenant) and I am very close to many fire fighting companies in my area.

The check valve is a good requirement. I would agree the primary purpose is for hydrostatic testing and to ensure the firefighters can use the same standard operating procedures as they would for any normally 'wet" fire department connection. If firefighters have a problem with one hose (during a fire), how would they change the hose without draining the entire standpipe system? Check valve allows a short duration with no flow and then they are back in business after connecting the replacement hose. This is just the best example I can think of off of the top of my head.

All of the nonsense about backflow preventors and pump backwash for a dry standpipe system is on the borderline of a complete waste of time.

 

[SprinklerDesigner2]

"If firefighters have a problem with one hose (during a fire), how would they change the hose without draining the entire standpipe system?"

Excellent point!

I've never been a fireman.

Thanks.

 

[PEDARRIN2]

Do dry manual standpipes have a valve at the hose connection?

I know dry automatic standpipes do - if they are using compressed air.

 

[Cidona]

PEDARRIN2,
If you mean do they have hoses at the required locations as oppossed to just having some kind of threaded outlet then yes, they have hose valves. Otherwise you would have water coming out all the locations when the FD started pumping water in. Is the hose valve, the valve you were speaking of?

 

[PEDARRIN2]

Yes.

That way there is a way to "seal" the piping.

Sometimes I have seen a cap on the end also, but that is not required.

 

[Cidona]

My understanding is that the caps are required to protected the threads.

 

[stookeyfpe]

The caps protect the threads. They are also designed to protect the interior of the standpipe from coke cans, tennis balls, dog poop, used diapers, and gatorade bottles. I've seen all of this and more shoved in FDCs.

Contrary to other posts, protective caps or covers ARE required. See NFPA 14 and IFC Section 913.

 

[PEDARRIN2]

stookeyfpe

I looked in NFPA 14 and the only requirement for caps was listed for class III standpipes. What about class I standpipes?

I couldn't find any requirement for caps in IFC 913. Could you be more specific?

 

[cdafd]

chapter 4 system components

4.8.2.1 Fire department connections shall be equipped with caps to protect the system from the entry of debris.

 

[Cidona]

Also required by NFPA 25.

 

[PEDARRIN2]

I always require the caps in my designs for the mentioned reasons. It just makes sense.

But I have also seen hose valves that were within a cabinet that did not have the caps on the end of the pipe.

Although required by the codes, the AHJ can "unrequire" about anything if they so desire. I am assuming the cabinet would meet the intent of protecting the threads and preventing people from adding materials to the pipe.