LD Hose use in Rural America

[gooselaketrain]

Hello all,

Hoping for some feedback from my brothers (And sisters) in Rural America.

Our small town has a pressurized water sytem with ground level storage tank around 50,000 gallons I believe. This system is newly installed a few years ago and with the new system we finally receieved a 6" water main with hydrants. Our department purchased a quanity of 5" LDH to take advantage of this hydrant system to help protect our school system. We are now being told that the use of this hose will destroy a entire water system if it is utilized.(The person who is saying this is a ex fire fighter who has a negative attitude concerning the department.....we took away the beer from the station) but who he approached our City council and complained.

I am looking for feed back positive or negative from any department that may be using this type of water system and have practical knowledge of how it performed for them

[MemphisE34a]

We are now being told that the use of this hose will destroy a entire water system if it is utilized.(The person who is saying this is a ex fire fighter who has a negative attitude concerning the department.....we took away the beer from the station) but who he approached our City council and complained.

Sounds made up to me. What does the water department say? Thats all I would worry about.

[ullrichk]

We use LDH to good effect in some areas with pitiful flows.

Next year, Tennessee state law will prevent us from hooking directly to any hydrant that flows less than 500 gpm, so we'll have to run longer lays in some areas to get to good hydrants. Last I checked, LDH is much cheaper than multiple 3" lays with a bunch of relay pumpers in between (the extra relay pumpers being the big expense).

LDH cannot damage your system unless you draw down the residual pressure past some given design pressure, usually 20 psi, but your jurisdiction may vary. The reason, I am told, is that you can draw untreated groundwater into the potable supply if the line pressure gets too low. You can do this just as easily without LDH.

[FyredUp]

gooselaketrain...

The village where I live and volunteer in has a water system that is fed by a 100,000 gallon water tower. The mains vary from 4 to 6 to 8 inch. We have never been told we can't hook to the water system with our LDH. We have neve3r damaged the water system either.

The hydrant doesn't know or care what size hose you hook to it. All the LDH does for you is allow you to get all the water that hydrant will supply farther from the hydrant than 2 1/2 or 3 inch hose will.

The one issue that can arise is slamming valves shut will have a big water hammer affect with ldh than with smaller supply lines.

Good luck.

FyredUp

[Dalmatian190]

No, it won't.

Unless your water system specifies otherwise, keep the residual pressure to 20psi, and also use soft suction as a "safety" that will collapse before you draw a vacuum on the system.

I would be a bit concerned with only a 50,000 gallon tank of how fast you'll drain the system, but I guess that partly depends on your well field -- It's worth a discussion with the water department to know what flow you can develop on a sustained basis from your hydrants. If your wells can only deliver 1,000gpm and you're flowing 2,000gpm from the hydrant...in less then an hour you're gonna have issues.

==========
Like Ulrich mentioned, the 20psi is used as a safety factor to keep from drawing a vacuum on the system.

20psi from a fire service perspective provides a cushion for the pump operator to react to a change.

20psi from the water service perspective keeps their system with positive pressure throughout it.

While it's doubtful we could draw enough of a vacuum (using soft suction) to collapse cast iron pipes, in certain relatively rare engineering systems you can create a vacuum on a remote part of the system with the remote possibility of sucking in contamination. The typical scenario for this is a long pipe that goes over a hill -- you may have your 20psi from elevation gain from the drop the pipe makes, but at the hilltop there's actually a vacuum that has developed that's helping "suck" the water over the hump. It's rare and oddball stuff like this that may have the hydraulic engineers place restrictions on the water system like higher minimum residual pressures.

That's really not a situation most areas should see that require a greater then 20psi residual.

[mcaldwell]

I would be a bit concerned with only a 50,000 gallon tank of how fast you'll drain the system, but I guess that partly depends on your well field -- It's worth a discussion with the water department to know what flow you can develop on a sustained basis from your hydrants. If your wells can only deliver 1,000gpm and you're flowing 2,000gpm from the hydrant...in less then an hour you're gonna have issues.

And I would like to know exactly what the guy was meaning when he said "Destroy" and entire system. Contamination or function?

If your municipal water pump is not designed to flow the same amount as your engines, you will quickly reduce the pressure below your 20psi residual, and your homeowners supply to a virtually useless flow. That may be what he meant, but in an emergency, that is really not your concern.

[JohnVBFD]

And I would like to know exactly what the guy was meaning when he said "Destroy" and entire system. Contamination or function?

"Spaceballs!!"

Oh Sh*t there goes the water supply.

[mcaldwell]

"Spaceballs!!"

Oh Sh*t there goes the water supply.

OK, This one's clearly going nowhere at Ludicrous speed.

[Dalmatian190]

I'm pretty sure McCaldwell knows this better then he phrased it:

If your municipal water pump is not designed to flow the same amount as your engines, you will quickly reduce the pressure below your 20psi residual,

If you have a hydrant that will flow 500gpm @ 20psi residual...

It's gonna flow 500gpm @ 20psi residual regardless of whether there's a 500gpm, 750gpm, 1500gpm, or 2000gpm pumper hooked up to it.

It's the whole fireflow v. recharge rate for the water system you have to look at.

Most water systems rely on the storage tanks -- elevated on legs or on hilltops -- as an efficient way to maintain pressure on the system thanks to gravity (elevation gain). As you draw water out of the system faster then it's replenished in the tanks, in most systems you'll see the pressure and thus the gpms you can get start to drop.

I guess the bottomline is understand your water system(s) and how it impacts you. On our public system, we know we can use 1 hydrant; if we open a 2nd even to fill a tanker we'll drop the residuals so low it trips water flow alarms. At the correctional center, we have water out the ying yang...thanks to a 500,000 gallon tank & 3,500gpm fire pump. However, that's being resupplied by the public system. If we lay a line in from the street, we'll impact the rate the tank is recharged -- theoretically we could flow 3,500gpm from the tank + 1,500gpm from the public system to provide 5,000gpm for about 2 hours, 20 minutes. At which point the tank is dry and you'd see a sudden drop in flow to the 1,500gpm the public system can provide.

While 1,500gpm is absolutely fabulous to have, we still maintain options around the hydranted area for secondary static water supplies for large or multiple incidents.

[mcaldwell]

I'm pretty sure McCaldwell knows this better then he phrased it:

If your municipal water pump is not designed to flow the same amount as your engines, you will quickly reduce the pressure below your 20psi residual,

If you have a hydrant that will flow 500gpm @ 20psi residual...

It's gonna flow 500gpm @ 20psi residual regardless of whether there's a 500gpm, 750gpm, 1500gpm, or 2000gpm pumper hooked up to it.

The clarity of the webernet stikes again.


Yup, I was trying to suggest that if he is in an old style "well" system, that relies on a supply pump for pressure (i.e. little or no gravity), he is going to be limited by the source regardless of the capacity of the grid. We never realized how limited our system used to be until we hooked 2 of our new 1050 pumpers up and ran the big guns. We took 100% of our systems capacity, but appeared to just barely maintain our residuals. Unfortunately, we were on the central 8" main, and didn't know the uphill feeders to the rest of the community were now left with NO residual. We didn't realize until one resident called to complain that thier water was "turned off".

Even if his grid can theoretically move 1500gpm, it won't help if his well pump only moves 500. He needs to see his flow tests, or talk to the public works staff to find out what his limits are.



Not to mention, filling a long lay of 5" LDH can take hundreds and hundreds of gallons even before the pumper sees a drop. Unleashing that amount of water through a wide open hydrant at the far end of the system can drop the system below his desired residual even before the municipal supply pump has time to fire up.

[gooselaketrain]

Thank you for the replies....well most of the replies..

I used this forum to vent out my frustrations over this topic...Most of this is a case of small town politics and some bruised egos. We checked with the engineering firm who designed this system and most of what you covered was repeated by the engineer.....Mainly keeping at least 20PSI in the main to prevent a vacuum in the system.

The remarks of this "Gentleman" who stated that the LDH would damage the system were printed in a local newspaper (Reporter was at the City Council Meeting) And much to our surprise we have been intidated with supportive calls from neighboring departments on our attempts to modernize our department. We have been actively trying to live down a reputation of being the "Good Old Boys" that was fostered by our previous chief.

Again thanks for the input and words of encourgagement.

Train hard and train safe

[SWLAFireDawg]

In my opinion, running the 5" hose is an excellent option, even if you only have the 2.5" connections at the hydrant. You still minimize the total friction loss through the supply hose to the engine, so you do get a little better water supply to your attack lines. And it allows you to make longer lays from the hydrant without the need for a relay.

If you have the big hose, run the big hose. At least that is how I think about it.

[FlyingRon]

If you're going to pump the hydrant, the hose size isn't as much of an issue as making sure you don't pull a suction (or drastically reduce the pressure) of the hydrant. Even before LD hose, we'd pump the hydrant with the the suction pipe and feed parallel 3" lines.

[ristomaki]

You will not damage your water distribution system regardless of what you attempt to flow from your hydrant system. That being said you will not likely need to utilize the 5" hose to reach the maximum flow available from your distribution sytem. My municipality currenly uses a direct pump type of water distribution system (no above ground water tower) and on a 6" water main located close to a 10" feed we are only able to get 600 gpm from the hydrant. The pressure with in the distribution system is 73psi. We have had our public works department test the hydrant to 600 gpm and we have calculated it using our pumper as well, wh have had no difficulty in achieving the maximum flow available using both 2 1/2" and 3" mdh hose. There is only one area in our municipalty where we can couse problems in private dwellings anfd the hydrant is located at the bottem of a large hill and the water main dead ends at the top of the hill.

hope that helps a little

[fire0099881]

Hello all,

we took away the beer from the station

not to hijack the thread, but would be interesting to know how you did that!

[dday05]

not to hijack the thread, but would be interesting to know how you did that!

Your question could be another discussion itself..

[neiowa]

Hello all,

Hoping for some feedback from my brothers (And sisters) in Rural America.

Our small town has a pressurized water sytem with ground level storage tank around 50,000 gallons I believe. This system is newly installed a few years ago and with the new system we finally receieved a 6" water main with hydrants. Our department purchased a quanity of 5" LDH to take advantage of this hydrant system to help protect our school system. We are now being told that the use of this hose will destroy a entire water system if it is utilized.(The person who is saying this is a ex fire fighter who has a negative attitude concerning the department.....we took away the beer from the station) but who he approached our City council and complained.

I am looking for feed back positive or negative from any department that may be using this type of water system and have practical knowledge of how it performed for them

Having been down this road with goofball "Rural Water System" going in our rural FD.

You said your system is "newly installed" so almost certainly PVC pipe (DR or SDR rating) rather than obsolete iron pipe. In discussions with the PVC pipe mfg trade association (Unibell) on this subject their staff engineer informed me that properly installed PVC pipe would not be damaged if you were able to pull a vacuum. You CAN NOT collapse a properly installed PVC main with a fire pumper truck. The soil supports the pipe and prevents deformation around the circumference of the pipe.

If your hydrant connection is soft suction (would anyone use anything else?) your suction line will collapse long before any other damage could to the water system.

Now "potentially" hammer "issues", or pressure changes in the vicinity of your hydrant, or elsewhere in the system, may result in temporary water flow/supply changes for other customers. Somewhere. Maybe. The water system operators are some of the most inside of the box/don't rock the boat bozos I've ever come across. If they don't have hydrants on "their" system then life is easy. I could care less how easy their life is. I could care less if grannies toilet fills slowly while her neighbors house is on fire. The water system is NOT "their" system. In nearly all cases it's bought and paid for with tax $ and/or user fees. For many years the $ for distribution systems has mostly been Fed CDBG $ and USDA Rural Dev $.

If the water system operator wants to claim potential "issues" with soft suction they need PROVE it. They get a qualified water engineer (most certainly such is not on staff/an employee) to model the system and demonstrate to you what the negative outcome will be when you hook up your pumper to hydrant #__ and pump to the capacity of the hydrant. Haestad Methods is the leading provider of the software required. If the won't go so, they need to STFU as they don't know what they are talking about and don't want you to prove it.

There are some restrictions you're just not going to get around and not worth fighting. For example in Iowa the Dept of Natural Resources (who reg water systems) will not allow a fire hydrant on a main less than 6".

[neiowa]

You will not damage your water distribution system regardless of what you attempt to flow from your hydrant system. That being said you will not likely need to utilize the 5" hose to reach the maximum flow available from your distribution sytem. My municipality currenly uses a direct pump type of water distribution system (no above ground water tower) and on a 6" water main located close to a 10" feed we are only able to get 600 gpm from the hydrant. The pressure with in the distribution system is 73psi. We have had our public works department test the hydrant to 600 gpm and we have calculated it using our pumper as well, wh have had no difficulty in achieving the maximum flow available using both 2 1/2" and 3" mdh hose. There is only one area in our municipalty where we can couse problems in private dwellings anfd the hydrant is located at the bottem of a large hill and the water main dead ends at the top of the hill.

hope that helps a little

You may have some undiagnosed problems in the system that need a qualified engineer to look at. Not much water from a 6" branch off a 10".

You need to talk them into installing a return line so have a loop. Even a small dia line would should make a substantial difference in flow. Deadend mains are bad and a symptom of a poorly designed system.