Thread: Relay pumping

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    Question Relay pumping

    Okay, this topic has probably been beat to death here, but I have missed those threads, so here's my question.

    Do any of your departments relay pump? If so, under what circumstances? What is the rationale for relay pumping?

    Any input (for, against, or otherwise) would be appreciated.

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    We relay pump when we have a long lay. Actually, our SOP is for a engine to pump at the hydrant if another lays in. That's even relay pumping.

    The rationale for relay pumping is that due to friction loss in long lays, you technically do not get the water supply that you need. Relay pumping boosts the pressure in the supply lines to overcome the friction loss.
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    We practice it occasionally for the reasons that Adze stated: Long lays. We have a lot of long twisty and pretty steep driveways in our area, where we may not be able to get the Engine or Tanker up close enough, so we would send the F350 up and do a reverse lay down to the Engine, and port-a-tanks, and go from there.

    Sometimes thats the only way to get the water where it needs to be.
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    I live in a town that does not have hydrants. So, we have 2 choices, relay, or shuttle. If we are VERY lucky, a water hole is within 2000ft away. But, we are still trained to dress a hydrant for mutual aid reasons.

    Scott

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    If we go over 4000' *and* want flows over 1000gpm. Life is good with 5".

    It's pretty rare for us to relay pump, and I think I've seen it more during drills than fire situations, although I've also seen an 8000' lay with significant elevation increase that used three relay pumpers.

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    We roll two engines on all structure fires, and our procedure is for the first-in engine to forward lay a supply line and for the second engine to set up at the hydrant and pump the relay. The main reason we do this is that we have only 3" supply line and the friction loss is too great to supply the first engine without some help. We'd like to get some 5" supply line but right now we are unable to make the financial commitment. Also, both of these engines have 1000 gallon tanks, so the relay pumper can provide its water to the attack engine while the water supply is being established.

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    Well, you're pretty much confirming what I thought. In a situation where your lay is say 500' maximum, through 5" hose, from a hydrant providing adequate volume, there wouldn't be a need to relay, right? I mean, if we're getting adequate gpm from the hydrant, and it's getting to our attack pumper with ANY pressure at all, our pumper should be able to boost the pressure as high as we need it, right? We don't need that water pushed to the attack pumper at 150 psi, do we?

    Also, by adding an unnecessary relay pumper, aren't we just adding one more link to the chain that can fail?

    And, talking to our best pump operator, he has told me that it's a lot harder to run the attack pumper when the relay pumper is pushing the water at him.

    Am I understanding you right? Am I making sense? There seems to be some disagreement regarding this topic in our department.

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    Thats what I thought till this past summer when we did a little training evolution during which we put one pumper at the hydrant then relayed to a second pumper (the attack pumper) The ammount of water available for use was dramatically increased
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    Originally posted by firemedicgm
    And, talking to our best pump operator, he has told me that it's a lot harder to run the attack pumper when the relay pumper is pushing the water at him..
    Ask him how is it harder to take water that is being forced in from a pumper than to take water that is forced in from a hydrant?

    At least with a pumper feeding you, you (the FD) can control the pressure of the intake water.

    You can regulate a hydrant with gates to decrease the pressure if needed, but you cannot increase the pressure unless you have a pump pushing it to you.
    Last edited by Adze39; 10-23-2003 at 01:22 PM.
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    And, talking to our best pump operator, he has told me that it's a lot harder to run the attack pumper when the relay pumper is pushing the water at him.
    This doesn't sound right. The relay pumper is simply boosting the pressure from the hydrant. Unless the relay operator is doing something that causes his discharge pressure to vary greatly like monkeying with the throttle, adjusting relief valves, or flowing discharges, the attack operator shouldn't have any problem. It should just seem like he's attached to a super-strong hydrant.

    If the intake pressure is greater than what the attack operator needs, he may have to gate down discharges or intakes but that can happen any time you hit a strong hydrant.
    Last edited by EFD840; 10-23-2003 at 01:31 PM.

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    It all depends on how much water you're trying to flow and over what distance. ALL hose has some amount of friction loss. I don't have my handy-dandy friction loss calculator with me right now, but I would think that 500' of 5" hose would have a very minimal amount of friction loss, and you probably wouldn't need a relay. However, the same distance of 2.5" or 3" hose would have a significant amount of friction loss, and you might need to boost the pressure to get the volume you need. Still, this is dependent on the amount of water you're actually flowing. That same 3" supply line might keep up with one or two 1.5" handlines, but add a couple more and maybe a deck gun, and you might not keep up. It's not whether the HYDRANT has the available water, it's how much pressure you're losing due to friction loss getting it from the hydrant to the nozzle. The more water you try to push through a given size line, the more the friction loss increases. Anybody out there have the figures handy?

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    It all depends on how much water you're trying to flow and over what distance

    Yeppers.

    Standard fireground intake pressure (minimum) is 20psi.

    That gives you a margin if something happens "upstream" to momentarily disrupt your water supply, and it the water & health department people don't like super-low residuals on hydrants.

    Say you have a hydrant that can develop 1500gpm with a 25psi residual.

    A) If you hook up a good 5" line, like Hi-Vol, you could put the pumper a whopping 50' away and still get full flow. That would give you 20psi intake, and 5psi to overcome friction.

    B) From the other perspective, how many GPM could go through the whole 500' with 5psi? 550gpm @ 500' -- in reality, probably more since as your flow went down, the residual on the hydrant would go up giving you more "umph". Probably 700-800gpm would be my average real-world guesstimate for 500' lay.

    C) Now, same hydrant still. 25psi residual @ 1500gpm. Hookup a 1500gpm pumper to the hydrant, you can now pump 150psi + 25psi incoming pressure and put out 1500gpm @ 175psi. That'll easily get you 1500gpm @ 500', indeed it'll go nearly 2,000'.

    D) One last scenario, let's have a really good hydrant. Say 1500gpm @ 60psi residual. Got 40psi to work with, and that's enough to send the whole 1500gpm through 500' of hose and leave 20psi pump intake pressure at the fireground.

    So, if your hydrants are like "B" and you're only working a house fire, 700gpm should be plenty and no need for a source or relay pumper.

    If your hydrants are like "C" and your working a commercial fire, especially going to master streams, best have a pumper on the hydrant.

    If you have great hydrants on a good grid, like "D", even for a commercial fire you don't need a source pumper.

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    Originally posted by firemedicgm
    And, talking to our best pump operator, he has told me that it's a lot harder to run the attack pumper when the relay pumper is pushing the water at him.
    The higher the pressure the water is when it comes into the attack pumper, the less the attack pumper has to work. This is regardless of whether that water is coming from a strong hydrant or from a relay pumper.

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    It's true that if the water is being forced from a pumper rather than a hydrant we (the FD) can control the water flow. However, the problem we have is exactly what EFD840 said - if the relay man is monkeying with the throttle, relief valves or discharges - then we aren't controlling the water flow very well. It's easier to run the pump when the intake remains constant, which it generally does from a hydrant (at least in our town).

    But the real question isn't "How will relay pumping affect this?" but rather "Is relay pumping necessary ?". If it isn't necessary, why screw around with it? We're only tying up an apparatus that could possibly be used elsewhere.

    The ammount of water available for use was dramatically increased
    I disagree with this statement. If your hydrant is flowing 1000 gpm, adding a relay pumper will increase the pressure, but cannot increase the volume - at least not without risking collapsing your main. Once you start drafting out of your hydrants, you're going to have some serious problems - and a very angry city council.

    The only way that a relay pumper could increase the volume of water available would be to open the tank to pump valve on your relay and allow the tank water to supplement the hydrant water. This WILL increase your volume - until the tank runs dry.

    So reviewing our situation with the new knowledge you guys have given me......

    Our department does not have trouble getting the minimum 20 psi pressure from our hydrants. We use good 5" intake hose, so there is minimal friction loss. A relay pumper cannot add volume to the water flow, only pressure (with the exception of the tank idea expressed above). At a single-family dwelling house fire, why would we ever need to relay pump?

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    Originally posted by firemedicgm
    if the relay man is monkeying with the throttle, relief valves or discharges
    Well, if he is monkeying with the controls, then maybe he shouldn't be a pump operator.
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    At a single-family dwelling house fire, why would we ever need to relay pump?
    Ever have 2 trucks hit 2 hydrants at once? If they are on the same line/grid, the pressure in those hydrants will vanish once the second hydrant is opened. You still have a 1000gpm hydrant, but it now has 10psi and that won't get you the water. We run into this often. If you never have a second hydrant hit, then you may not have to worry about it.
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    The higher the pressure the water is when it comes into the attack pumper, the less the attack pumper has to work.

    Which isn't necessarily here nor there.

    If you have 150psi coming in, you're gonna be almost throttled down and/or having to gate back discharges to keep their pressures reasonable to the flow.

    Our fire pumps would be happy campers to have 150psi intake and add another 150psi and have 300psi discharges. Guys on the knob are probably not going to be happy campers!

    Throw in someone monkeying at a relay pumper, the fireground guy is constantly pulling and pushing levers to try and keep his discharge pressures even and reasonable.

    A relay pumper cannot add volume to the water flow, only pressure
    With the clarification that by adding pressure to overcome friction loss (which is higher at higher flows), a relay pumper allows that volume to be delivered further.

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    Here in downtown Maryland, I don't have any 5" hose, nor do I want any. We have reasonably close hydrant spacing (300 Ft in some areas, 600 in most) good mains with good pressure, AND, you will always find an engine on the hydrant. Period. We demand the control and flexibility that a source pump gives us, and our operations are better for it. On a single family dwelling, we never (that's right, I said NEVER) get fewer than 3 engines on the initial dispatch, quite often, more will show up. First engine lays 1 or 2 3" lines from the hydrant, 2nd engine hooks into hydrant, 3rd engine stands by at the next available hydrant, to bring in a backup supply if needed. If additional engines are running, the 4th will pick up the backup hydrant, and the others will stage out of the way. Multifamily residential and commercial alarms get at least 4 engines, and the operation is the same, if there is a building system, the first engine hooks into it. Why no LDH? Once a LDH line is charged, there is no getting over it, this effectively blocks out later arriving apparatus (among other things). We do have several units with 5" LDH, they are special called as needed, thankfully not often. Stay Safe....
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    HWOODS, So what you are saying is that most of your fires are controlled by either 1 or 2 3 inch lines. Must be nice to have those types of fires. I understand the moveability of the LDH, But here we do not have that luxury of having 3 engines because of smaller Volley company and we do not have the luxury of close proximity to hydrants everywhere, nor do we have the luxury of all the toys you all have down there. So Relay pumping does come into play for us on calls outside the village and in mutual aid areas.

    Like others, we either have the pump at the water source or in line where needed for boosting the pressure, not the volume just the pressure. All engines lay in forward on 99% of the calls, but we still train on the reverse lays for the occasional call when we need to utilize that also.

    Chief, you all got your act down there in that neck of the woods though I will admitt that. Stopped by one of the stations a couple years ago, and you all have a real nice set up and some down right intelligent people that knew everything about your operations.


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    In Baltimore County, Maryland we have a term called "Heavy Water Hookup" for our hydranted areas that is very rarely used now that most companies run 4 and 5 inch LDH. The real oldtimers tell me it was used a lot back in the days of single and dual 3" supply lines. Us old guys still train "the kids" on it.

    We use Humat hydrant valves and typically if the first engine drops a line this line is connected to the hydrant at the steamer outlet and a water supply is established. For those of you not familiar with a Humat, it has one steamer connection with a clapper and then has two outlets that are controlled by a pressure sensitive clapper valve and one that is controlled by a manual vavle. One of the side connections is attached to the supply line and the other is open. The second engine hits the plug and can hook up to the hydrant to boost the pressure if necessary. The second engine connects to the Humat with a suction hose and then connects a discharge line to the open side connection. The manual valve is opened to allow water to enter the relay engine's pump where it is discharged back into the hydrant valve. The pressure actuated flapper opens and the pressure boosted water is sent on it's way to the attack engine.

    The beauty of the Humat is that the supply to the initial attack engine is uninterrupted while the heavy water hookup is taking place.

    In non hydrant areas, we typically have an engine at the fire scene which lays a line from the end of the driveway or access into the scene. A second engine and a drop tank are set up at that point to supply the attack engine and a shuttle is run to keep the porta-tank full.

    Harve, you are right. LDH can be a real pain in the butt if it's not layed right. We've invested in some hose ramps for cross streets and we train our PO's to try to keep the line along the road shoulder or curb as they lay out. If we have sufficient bodies, we will move the line to the side before we charge it. Not always possible though. If you have a worker, tank water doesn't last long
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    We are are all totally hydranted and we run soon to be all 5" LDH.He have a couple of places that are 1500'from the nearest hydrant and these are in industrial areas that have only yard hydrants with 2.5" connections. So our rule of thumb is forward lay first engine and next due attaches to the first one and completes the lay to the scene.
    Also, as previous posters noted it is the same gpm only under more pressure.
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    Default 4"

    SOP here is every 800' have a pumper,rarely used though cause of hydrent spaceing being 500'.

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    Default no ldh discharge

    Our pumpers do not have ldh discharges. How efficient is it to relay out of a 2.5 discharge into LDH? Since we have had LDH we have only ran it strait off the hydrant.

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    Our pumpers do not have ldh discharges. How efficient is it to relay out of a 2.5 discharge into LDH? Since we have had LDH we have only ran it strait off the hydrant.
    Hmmm. I dont think it would be very efficent with 2.5". Your maximum effiecnt flow would be 500 gpm with 2 lines, thats half the capcity of a single 4"line and 1/4 the capcity of a 5" line. I see alot of problems with pressure and volume--course I could be wrong.

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    Default Re: no ldh discharge

    Originally posted by gregblewett
    Our pumpers do not have ldh discharges. How efficient is it to relay out of a 2.5 discharge into LDH? Since we have had LDH we have only ran it strait off the hydrant.
    The reason one uses LDH is to eliminate the friction loss created by attempting to shove a large volume of water over a long distance thru a straw. Can't do it with tiny hose dia, use LDH to reduce the friction loss. Outlet dia on your truck is not the critical issue, use an adapter on the pumper outlet if required.

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