2-way hydrant procedures

[dmleblanc]

OK, so a neighboring chief and I were having this discussion the other day about how our respective departments hook up to the hydrant. We both recently converted to LDH (he has 4", we have 5"). The subject of 2-way hydrants came up, that is, a hydrant with only the two 2.5" outlets and no steamer connection (we both still have many of these in our districts).

Anyway, in his department they rigged up a pack for this situation, which consists of two 25' sections of 3" hose which are connected to a siamese, which can then be connected to the truck or to the 4" supply line. In our department, we carry a hydant bag on every engine, and in that bag is a
2.5" x 5" Storz adapter, so we can connect the 5" LDH directly to the 2.5" outlet. The other outlet gets a gate valve for possible additional hookups.

Now, my question for you engineer types is this...which setup is better? His argument that any time you use both outlets you'll get more flow than only using one. My theory is that you'll get at least as much flow through the less restricted 5", even if only using one outlet. And how much difference does it make that I am using 5" and he is feeding those two lines into a 4"?

I'm no master of hydraulics, so maybe someone who has done the math can enlighten me on this one

[FyredUp]

Ah, the infamous 2-3-4 set up. A metro FD near me uses that, or they did when they used 4 inch hose. Not sure what they would do now since they switched to 5 inch.

I am a firm believer in using the 5 to 2 1/2 adapter and valving the other outlet. I think the restriction for that short distance won't make a significant difference. But by vlaving the other side if there is more available you can always hook that side up too.

[Dickey]

You will only get as much water out of the hydrant as the HYDRANT openings will allow. Regardless of what hose you attach to it, you will only get a maximum of what the 2 1/2 outlets will allow from from the hydrant no matter what combination of hose and adapters you hook up to it.

[WD6956]

You will only get as much water out of the hydrant as the HYDRANT openings will allow. Regardless of what hose you attach to it, you will only get a maximum of what the 2 1/2 outlets will allow from from the hydrant no matter what combination of hose and adapters you hook up to it.

Agreed. But would'nt TWO 2.5 outlets flow more then one? With that in mind, i would think the dual 3" hose to a siamese would give you more volume then a single 3" hose. Adding the gate to the second outlet would be fine as well because if nessecary, you can tap that as well.

[Acklan]

Now, my question for you engineer types is this...which setup is better?

Chief run a test at your next pump ops training. Lay a stretch of 5" and 4" . Record the static pressure, then the residual pressures between the different configurations. I would us 300"+ of hose just so the difference would be very obvious.
In the '80s Jackson Fire Dept. (Mississippi) did a simular test and found the difference was almost none existent. I believe the article ran in "Fire Engineering".
If you use the rule applied when figuring friction loss, the simiese and hose should represent at least 25 psi in friction loss. That is what is required for an appliance.
dmleblanc still looking to buy lunch next time you are in town.

[RFDACM02]

You will only get as much water out of the hydrant as the HYDRANT openings will allow. Regardless of what hose you attach to it, you will only get a maximum of what the 2 1/2 outlets will allow from from the hydrant no matter what combination of hose and adapters you hook up to it.

Of course this is a true statement, but the real question is how much will a 2.5" outlet flow? If you're stuck on hose flow numbers you've already lost. Considering a 2" master stream nozzle will flow 1000 gpm at 80 psi, I think you'l find the single 2.5" port will flow plenty into LDH hose, likely making it an overall more efficient operation.

If I'm figuring right, and by this I mean using the right internet calculator, I find that a single hydrant 2.5" port will flow 1280 gpm at 50 psi using a orifice constant of .97?

I'm thinking dual 3" lines even at 25" long plus a siamese (10 psi appliance loss) will not gain a lot of flow before reducing the incoming pressure to below 20 psi (standard incoming psi?). So given the added work, I doubt it's worth it.

[dmleblanc]

Agreed. But would'nt TWO 2.5 outlets flow more then one? With that in mind, i would think the dual 3" hose to a siamese would give you more volume then a single 3" hose. Adding the gate to the second outlet would be fine as well because if nessecary, you can tap that as well.

I totally agree, the dual 3" lines would flow more than a single 3" line. But will they flow more than a single 5" LDH, that's my question.

dmleblanc still looking to buy lunch next time you are in town.

I'll have to take you up on that one day...I only get up to Baton Rouge once in a blue moon, though...

[dmleblanc]

If I'm figuring right, and by this I mean using the right internet calculator, I find that a single hydrant 2.5" port will flow 1280 gpm at 50 psi using a orifice constant of .97?

.

This is also a part of the equation. In general, the hydrants in his area have considerably better flows than ours. Even at 20 psi residual, most of my hydrants flow less than 1200 gpm. So the way I see it, the hydrant is maxed out through the one 2.5" outlet. This may not be the case in his area, where he gets more than 1500 gpm out of some of his hydrants.

Of course, most of the 2 way hydrants we have are in really poor water areas (some flow less than 500 gpm), so in these areas tapping one or both outlets really won't make a difference.

I agree with Acklan, the best way to know for sure would be to set it up both ways and try it out.

[LaFireEducator]

My last department went through this discussion when we got 4".

Luckily, most of our hydrants had steamers.

We did have a few that did not. Initially we hooked a 3" line to both discharges, then used a siamese at the 4" line. About 6 months in, we did flow tests and found that the second line only boosted the flow by about 10%,or in our case, about 80gpm. We decided that slight additional flow wasn't worth the work and time, and started connecting a single 4" directly to the hydrant. We did gate off the second discharge.

[Acklan]

Placing a 2.5" gate valve would give the option to lay a second 4"\5" if the need arises. No different than laying dual 2.5" or 3" lines. Whether the benifit is there would be up to your department.

[RFDACM02]

Placing a 2.5" gate valve would give the option to lay a second 4"\5" if the need arises. No different than laying dual 2.5" or 3" lines. Whether the benifit is there would be up to your department.

Oh now that's just crazy!! You mean we could lay a second LDH to the engine if the hydrant could actually supply it? No siamese needed either since most engines that use LDH are set up to receive at least two LDH. We do this on our standard hydrants. Hook the steamer and add one gate valve with an adapter to LDH on it.

[FFWALT]

As with anything it is best to run the experiment yourself but over a distance 5" LDH will probably outflow two 3" running the same distance.

When I first got started pumping we had a pump class and did this very same thing over about 300'. That made me understand when friction loss was. You saw a pretty significant decrease when you switched from the LDH to the 3".

Since I'm Bohemian I'll try to use my Bohemian analogy for friction loss. It reminds me of an onion you cut in half so you see the rings. The outer ring is what drags against the hose and creates friction loss. The two 3" have a larger diameter but also a larger area for friction loss to occur. The 5" has less water dragging against the jacket so it is capable of flowing more water with less friction loss. That's just the picture in my head I use to explain it, I know someone will have the text book example and definition.

Now if the hydrant is capable of flowing more capacity than one 2 1/2" outlet could supply then it would be beneficial to use the two short pieces of 3" into a Siamese. I've also been told that a 2 1/2" x 5" LDH adapter at the hydrant will provide 80% of the flow that the steamer would. Keep in mind that is what I have been told and have nothing statistical to back it up so take it with a grain of salt until you determine it for yourself.

[CaptOldTimer]

Chief,


Old double deuce and a half hydrants. I thought they have all vanished. We had many of them for years and use a 3 inch X 10 foot hard suction, we called the "Monkey Tail" suction. We use that to make the hydrant to pumper connection.


Here is an idea that we used for those old style hydrants, until the water department could replace them with the newer hydrants.


We had two twenty-five foot sections of 3 inch going into a Siamese which in turn will go to the LDH, be it 4 or 5 inch, which would lead to the engine at the scene. Make the hydrant and connect both 3 inch section to the discharge outlets. The Siamese connects to the 4 inch LDH and once they driver is ready for water, charge the lines. I can't recall the amount of water reaching the pumper, but it was more than enough for any structure type fire.


Of course, if the company made a hydrant that had a steamer outlet, then the LDH went directly to the steamer outlet.

[RFDACM02]

Chief,


Old double deuce and a half hydrants. I thought they have all vanished. We had many of them for years and use a 3 inch X 10 foot hard suction, we called the "Monkey Tail" suction. We use that to make the hydrant to pumper connection.


Here is an idea that we used for those old style hydrants, until the water department could replace them with the newer hydrants.


We had two twenty-five foot sections of 3 inch going into a Siamese which in turn will go to the LDH, be it 4 or 5 inch, which would lead to the engine at the scene. Make the hydrant and connect both 3 inch section to the discharge outlets. The Siamese connects to the 4 inch LDH and once they driver is ready for water, charge the lines. I can't recall the amount of water reaching the pumper, but it was more than enough for any structure type fire.


Of course, if the company made a hydrant that had a steamer outlet, then the LDH went directly to the steamer outlet.

Sounds kjust like what the OP was describing as one FD's system. The question is: Would just using a single 2.5" outlet with a 2.5"xLDH connection to supply the LDH directly to the engine be as good if not better?

[CaptOldTimer]

Sounds kjust like what the OP was describing as one FD's system. The question is: Would just using a single 2.5" outlet with a 2.5"xLDH connection to supply the LDH directly to the engine be as good if not better?

It would and also depends on the water available and on the lay out of the LDH. If you drop 300 to 500 foot of 4 inch you are going to get ample water if the hydrant has the water. You will get better with both outlets supplying the LDH.

They need to lay it out in various meathods to find the one best suited for them.

If worked great for us when we had the old hydrants. We tried it both ways.

[pvfd27]

Long, long ago... there was an article in a trade magazine (not FH) that tested a hydrant with 2 - 2.5's and a 4.5 steamer with 4" hose. Really wish I could be more specific with the source and numbers but the results were basically as follows: most flow was from the steamer to 4", followed by 1 2.5" gate to 4" and finally the 2 2.5" gates siamesed to the 4". The surprise with the single gate over both gates was due to friction loss with the siamese appliance. Never actually flow tested it ourselves.


We don't have hydrants without steamers so our sog is to connect with a hydrant assist valve and at least one 2.5" gate.

[MemphisE34a]

You will only get as much water out of the hydrant as the HYDRANT openings will allow. Regardless of what hose you attach to it, you will only get a maximum of what the 2 1/2 outlets will allow from from the hydrant no matter what combination of hose and adapters you hook up to it.

Technically you are correct, BUT friction loss is lost through hose, not discharge ports on a hydrant. A single 2 1/2" discharge will flow 80% of the capacity of the hydrant. So yes, (2) lines will get you more, but only 20% more. All other pressure and flow is lost through the hose from the hydrant to the pumper.

So, IMO, the best possible scenario would be to start with a single, short section of 2 1/2" or 3" hose to a supply pumper on the hydrant to pump the line to the attack engine in order to overcome the GPM and pressure loss through the hose from the hydrant to the attack engine.

If this is not possible, lay dual lines. Not necessarily to get more water out of the hydrant, but to not lose so much through the fire hose along the way.

[RFDACM02]

So, IMO, the best possible scenario would be to start with a single, short section of 2 1/2" or 3" hose to a supply pumper on the hydrant to pump the line to the attack engine in order to overcome the GPM and pressure loss through the hose from the hydrant to the attack engine.

So would you agree that this scenario would be best with a single short length of LDH? Thus minimizing the FL in the hose to it's absolute lowest?

[MemphisE34a]

So would you agree that this scenario would be best with a single short length of LDH? Thus minimizing the FL in the hose to it's absolute lowest?

AHHHHH!! I evidently got side tracked talking about the 2 1/2" discharge that I completely forgot about the LDH.


Agreed!!

[MG3610]

Use both 2 1/2" ports and use 5" Hose, otherwise you'll never get the capacity.

Using smaller hose, you will see losses of the water in the hose. A siamese to single 5" may seem easiest, but takes more connections. I say start with a single line of LDH, gate the second port and add the second supply line once the first is going.

Email me for that article, its too big for me to post here.
mg0178@yahoo.com