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.
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.
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.
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