02-16-2001, 04:54 PM #1S. CheathamFirehouse.com Guest
5in. supply line in poor hydrant areas?
My small volunteer department is in the midst of a battle over replacing our 3in hose with 5in hose. We have some good hydrants in town, however our commercial area has all old Eddy Vaine (only 2-21/2 inch outlets) hydrants with only about 400-750gpm at 40-50psi (provides about 600-800gpm with two 3in hoses) on 4in mains. Our current SOP is to wrap a hydrant with two 3in hoses and forward lay a pumper to the fire structure. The second engine connects to the hydrant and supplies the 3in laid by the first in pumper. If more water is needed we send other engines to other hydrants 3-4 blocks away. Proponent of the 5in, and I am one of them, want the first pumper to hook to the hydrant and forward lay to the structure. The second engine could then reverse/forward lay, whichever is necessary, to another hydrant and supply the ladder or another pumper. I know have read Shapiro and all the literature out there and I know it will work theoretically, but I would like to hear from others who have similar hydranted areas and use 5in and from anyone else who might have a good opinion. FYI: The town plans to replace these hydrants and mains, however not for another 5-10 years.
02-16-2001, 11:02 PM #2ffengFirehouse.com Guest
S. - I think your right on the money. If you want to, go to the Engineer forum, look for a 5 vs. 6" post by Joey. I worked out some 4" vs. 5" vs. 6" supply lines for the same hydrant.
Your choice of supply line size really shouldn't be based on the type of hydrant (steamer or not) or water supply available. Basically, bigger is better (generally) no matter what the hydrant or supply is. By using larger diam supply line, you cut friction loss dramatically. A hydrant provides a certain water supply (pressure and volume). By using larger diam supply line, you can essentially "move" the hydrant anywhere you want and not lose any of that pressure/volume supply. How much of advantage the larger lines are depends on the flows available (friction loss increases with increasing flow) and how long the lays are. Example, an FD with 4" and low flow hydrants and very short lays may not see much difference going from 4" to 5". Here, the 4" may already be negligible friction loss so going to the 5" doesn't buy you much.
In your case, I can almost bet that going from 3" to 5" will be a noticeable improvement.
The only issue you really have to watch in this case is just watch your intake pressure and don't go to low. Other than that, pump everything you got.
All you have to have is a 2 1/2" to 5" storz adapter for the hydrant, and away you go. If you also have steamers, just keep a steamer and a 2 1/2" to storz with your hydrant bag/tools, etc. and your all set.
Forward lay the 5" for the first due is definitely a reasonable way to go.
If you have some actual hydrant flow data (static and residual flowing xx gpm) and how far is your typical lay, put them up here and we'll calc out what the 5" will buy you.
02-16-2001, 11:17 PM #3StaylowFirehouse.com Guest
I think the 5 in. would work great in your case. Particularly in those areas where you have lower pressure. The larger hose will have far less friction loss, so you're supply will be improved. I think that your water supply can dictate the type of supply lines you should run, and in your case the larger hose would make a large difference.
02-16-2001, 11:32 PM #4Dalmatian90Firehouse.com Guest
Hydrants found frequently, of high pressure, and modest volume or less --> Use small hose if you must.
Hydrants of any distribution, of any pressure, of any volume --> Use LDH whenever you can.
02-17-2001, 11:23 AM #5ffengFirehouse.com Guest
I made up a hydrant and did some calcs on it with various supply lines:
Hydrant - 70 psi static/500 gpm @ 50 psi residual; this hydrant would flow about 900 gpm with 10 psi residual pressure.
Here's what you get:
At 100' from the hydrant:
Single 3" - 550 gpm @ 10 psi residual
Dual 3" - 750 gpm @ 10 psi residual
Single 4" - 775 gpm @ 10 psi residual
Single 5" - 875 gpm @ 10 psi residual
At 500' from hydrant:
Single 3" - 300 gpm @ 10 psi residual
Dual 3" - 500 gpm @ 10 psi residual
Single 4" - 550 gpm @ 10 psi residual
Single 5" - 750 gpm @ 10 psi residual
Dual 5" - 825 gpm @ 10 psi residual
You can see that at 100', the dual 3" vs. 4" vs. 5" is not all that great. Going from dual 3" to 5" buys you 125 gpm. Dual 3" is already getting you 750 gpm out of a max of 900 gpm @ at 10 psi residual so going to LDH here isn't a great advantage.
Things change though at 500'. The dual 3" drops to 500 gpm, so you've lost almost half the 900 gpm max that the hydrant could supply. However, with the 5", you still have 750 gpm out of 900 gpm max to use. I also threw in dual 5" at 500'. Here you would get 825 gpm out of the max 900 gpm at 500'. Going from dual 3" to 5" at 500' increases your supply by 50%. And as you go longer than 500', the differences between the supply line size gets greater.
As you can see, for this hydrant and in the 100-500' range, going from dual 3" to single 4" LDH probably isn't worth it. But dual 3" to 5" LDH is a major difference.
So it's really in the length of the lays. You mentioned having a second engine lay to another hydrant. I would say anything beyond 200 ft. or so, you really have to use 5" to have any flow/pressure left that's worth having.
I hope this helps. Again, if you have actual hydrant flow test data and want a specific supply line length calc'd, put it up and we'll do it.
02-17-2001, 08:38 PM #6S. CookFirehouse.com Guest
"I know have read Shapiro and all the literature out there and I know it will work theoretically"
Shapiro actually did these tests and they are described in his book "Layin' the Big Lines." Theoretically it actually turned out a pretty good case for changing to LDH.
Why not get the water department to pay for your 5"? That's what we did.
City annexed a mile down the highway with plans to add water in 3 years.
FD to city - we can't cover that area, we don't have the water supply.
City - What do you need?
FD - 6600' of 5" hose.
City - it's not in your budget.
FD - this is a water problem not a FD problem, take it out of the water budget.
City - great idea, send us the specs so we can bid it out.
You might be able to do something similar. Get the needed fire flows of the buildings, tell the city you can't meet the demands if you can't (be honest) and if 5" will help now or in the future, ask for it now.
Do all of this in a letter to the city. That way if one of the buildings goes to the ground and the news boys start asking why you let it burn, you can put it off on the city: "hey, we told them 6 months ago we didn't have what it takes to put this fire out. For a measly amount of capitol outlay we'd at least had a chance - here's a copy of the letter, see for yourself" or something like that.
[This message has been edited by S. Cook (edited 02-17-2001).]
02-18-2001, 03:20 PM #7ffengFirehouse.com Guest
The questions that you ask can be answered very accurately using the basic concepts of hydraulics and fluid flow. Fellows like Bernoulli (late 1600's to 1700's), Henry Darcy and Julies Weisbach (in the mid 1800's) and Gardner Williams and Allen Hazen (from the early 1900's) through testing and experimentation developed most of the hydraulic principles used today.
Based on these principles and formulas, you can accurately calculate the diferences in hose sizes or hose lays or using different hydrants or the impact of elevation, etc. If you know basic characteristics such as type of pipe or hose, diameter, length, etc., you can calculate accurately the impact on volume and pressure, etc.
The concepts of hydraulics have been proven over the course of over 300 years.
We use software where you can take a municipal water system, input actual flow data from a hand full of hydrants, and model(calculate) accurately the available flow at any hydrant. We can do this during the day when normal demand is greatest, or at night, or with multiple hydrants flowing, etc.
There are obviously other considerations like funds, existing equipment, compatibility with mutual aid depts, that may influence any decision, but the evaluation tools needed to determine the differences between different supply line size and the impact on available water supply are readily available and accurate.
02-18-2001, 06:23 PM #8S. CookFirehouse.com Guest
ffeng - what is this software you speak of?
02-22-2001, 07:59 PM #9RRepaskyFirehouse.com Guest
I know exactly what you're going through. After reading everyone else's replies, I think you already have your answer. We went through this whole process about 12 years ago. I'll never forget our borough council president, who by the way, was a past Chief of the department, saying he could get more water out of 2, 3inch lines than 1, 5inch line. He had the whole town convinced that with 2, 3inch lines, you have 6 inches. We spent a whole Sunday laying out 5" hose from other departments that already had it and layed the same amount of dual 3 inch along side. We invited the whole town including the town council. Needless to say, the president never came. Anyway, the bottom line is that we proved that 5" was better. After this, we didn't have much of a problem getting the hose. In fact, we got all the departments in 3 counties across 2 states and got everyone on board. We put out bids to SnapTite, Angus, and others for about 30,000ft of 5" hose plus appliances. It was awarded to SnapTite and was one of the biggest bulk purchases they ever had. It was also a huge savings to us.
Robert Repasky, Asst. Chief
Sayre Fire Dept.
03-05-2001, 12:25 PM #10chiefnapeFirehouse.com Guest
I am going thru the same thing at my department. Even though I am the chief, the older members cannot figure out why they cannot supply 3 1 3/4 lines with one 3" line. We are slowly changing over to the 5"ldh and we love it. Keep the ball rolling and you will see the change.
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