I recently came in contact with a department that was looking to change from 5" LDH to 4" LDH, I Know that I work for a department that made the change in the opposite direction, saying that the one inch differece, was big to the extent of close to double the friction loss when moving big water. I would like to hear any other feed back from you all, so that when I debate with this desk commander, I can present a good case. I think they main objective is the weight and size of the hose when it is charged, which is in my opinion, most of the time when your needing a supply line its because you have a big enough fire that you need water, why not have alot of water.

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Most depts in our area use 2.5 to 3 inch supply hose. Some have 4 or 5 inch on their pumpers in some areas.

We also have one station which operates as a water supply company which they have most of their units with 5 inch and have 2000 GPM or better pumps on their engines. They run on second alarm box alarms or non hydrant areas along with water tankers.

Mark,  I know the type...don't confuse me w/ the facts, my mind is made up.   If the calculations/FL etc don't work then get the weights of the various hoses from each manufacturer and show them to "the don't confuse me" crowd.  Again facts might not work but that was the route I took w/ my guys and I was able to find a manufacturer of 5" LDH that weighed very close (9 lbs per 100') to the 4" we had.  I was making the change for 2 reasons...replacement of aging 4" LDH and upgrading the LDH to match the current and future pump capacities of our dept.  Generally 4" works well w/ up 1000 gpm pumps/flows over reasonable distances (1500' +-) and 5" for larger pump capacities or longer lays.  I asked our guys when was the last time any of them picked up an entire length anyways.  Those that raised their hand were then asked if they could pick up a ten lb weight.  Nobody said they couldn't so I bought the 5" hose. The only other comment I would make is in figuring FL on long lays make sure your able to stay w/i hose specs for max pressure...usually 180-200 psi for most LDH.  If the FL combined w/ any elevation loss is more than about 150-160 psi (leaving 20# residual @ intake) you will be exceeding the specs and could dmg the hose or more importantly injure a FF.  Good luck.  BTW we added 4x5 stortz adapters on each truck anyways as we have MA depts using 2 1/2", 3", 4", and 5".
You could always go with attack rated LDH and pump the higher pressures.  Snap-Tite has some LDH, both 4 and 5 inch, rated at 300 psi service test.

Mercedes Textiles also has some hose rated at higher pressures w/ low FL numbers.  We have been buying that for our last 3 trucks but we still have some older "plastic" hose that is not rated as high and we are careful about our pressures w/ the mixed brands.  I am replacing all the LDH on 1 engine per yr. along w/ the associated fittings needed for each truck (intakes etc).

 

Frankly, I'm still curious on the financial aspect of things. If nothing else, where is the cost savings in switching to a smaller line? You already have 5", and I'm doubting all the hose can't pass a hydro test, which means there has to be a cost incurred to switch all your LDH from 5" to 4". Also, on the same token, comes in purchasing adapters for a different size hose. In the end, even if a grant is involved, the financial aspect does not make sense to switch hose sizes.

 

I could honestly see an argument to go from 4" to 5", but not the reverse. To me it is just asinine to even contemplate such a move and ability to move the hose is a poor excuse, because seriously, how often do you need to move a charged LDH? To me it is a no brainer to stay with the 5", there is probably more items and more usefullness that can be purchased with the funds rather than swapping out all the LDH.

 

IMO, people even considering such changes makes my head spin.

I can't believe people are still using 2 1/2" and 3" for supply lines.  Evidently, a lot of dept's have never read the report on the Super Sofa fire.  My full time dept. has been using 5" since the '70's, and the rural dept. I'm on started switching to 5" over 5 years ago.  Some fires may even call for double 5" lays.  GPM's put out fires people.
Or maybe we just know how to properly do our job?  I don't think you really have the right to say it's wrong for us if you don't know about our departments.  Two of us who said we use 3" work in DC and Indy which are two urban cities.  In DC we have hydrants EVERYWHERE.  With our good staffing we get quick responses which means smaller fires.  In the rare case we DO have a big fire we have a water supply engine in each battalion with 5" hose.  3" still works great in out city so there's no reason to change.
Thanks Glen for your input, I know I have an uphill battle. I been trying to hit them on the FL side, pushing the case of getting towards the capacity of the pumper supplying the aerial, meaning that once we start pushing the pump pressure over 150 psi, we have to start dropping the gpm the pump is rated for.
Yet another reason for going with 4" is that may be the most GPMs the hydrants will flow and a lack of other water sources. I'll also agree that departments that can get in quick can make a good knockdown with even just tank water (I've always maintained that if you can't get a good knockdown with tank water, the battle was lost to begin with), then mop up with a 2 /12" or 3" supply line. In my own County Department we use 5" as our supply line. Where we have hydrants, they are usually ample to supply adequate GPMs. All of our apparatus are also equipped with 2 1/2" that can also be used for a supply line for smaller fires, etc. Dump tanks are widely used in our rural areas. Would have to say that each Department has its unique needs and when sizing supply line, there is no one-size-fits-all approach.

The only reasons not to change to LDH are 1) This is how we have always done it.  2)  Change is expensive in larger departments.  It is cheaper to keep buying replacement hose of the same size than to try and replace it all with something different.  Although it would be relatively fiscally responsible to change out a rig or 2 a year with LDH. 

Everything that you do with single or multiple 2 1/2 or 3 inch lines can be done better with higher flows and efficiency with LDH, inclucing reverse lays.

 

The fact is FLOW is the key and the way to get EVERYTHING a hydrant has to offer in GPM is using LDH.  Many people lose the idea that a poor hydrant benefits as much as a good hydrant from LDH.  The reduction in friction loss using LDH allows that poor hydrant to move ALL of its water farther than laying 2 1/2 or 3 inch lines, and most often without having to pump the line.  A good, high flow hydrant dressed with LDH will move more water farther again with a single line and usually not having to pump it over normal distances.

 

Both of my POC FDs are rural and both carry and use LDH in both hydrant and rural operations.  We are experiencing people buying chunks of rural land and having long, narrow, winding driveways to allow for maximum privacy.  It also leads to driveways that it is virtually impossible to run a practical and efficient tanke shuttle.  So what we do is lay 5 inch up the driveway leave the tanker shuttle at the road.

 

I couldn't more starongly disagree that if you don't get the fire with the tank water you have lost the fire.  That might have some validity if we are talking about smaller single family dwellings, but most certainly not to barns, farm buildins, businesses, multi-family apartment buildings, industrial buildings, and the McMansions city folks like to build out here in the country.  Building a water supply, whether in town off from hydrants, or in the rural with foldatanks and tankers (yeah yeah, I know tenders), is a crucial element to a successful fire attack.  Further if it does get away from you you will need the water for defensive ops and exposure protection.

 

Here the thing, I am talking florida.... and with that being said, average number of people on the engine 3 maybe 4 at best. Have time for 1 lay, and the average distance between hydrants 800-900 feet minimum. For the most part, if the supply line is going down, its to supply the stick, when the stick goes up, the building comes down.. had to add some humor.... So what you said, you have to consider the community that you serve and the available resources.
For those of you having trouble breaking the storz couplings one thing I found is that sometimes the gasket unseats especially at high pressure like when hose testing.  However I haven't found a way to keep it from happening. As far as the 5" vs 4" the city department I was with used 5" hose. When it costs around $500 to $800 per 100ft section I would half to agree that the money could be better spent somewhere else.

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