Thread: Relay pumping

  1. #1
    david2 Guest

    Question Relay pumping

    in a relay operation how much water can you get when you hook a 4 inch hose to a 2.5 intake in a 100 foot relay pumping to a 1000 gpm pumper from a 1000gpm pumper the # 1 pumper does not have a press. intake valve the 4 inch hose hooks to the 2.5 intake on the side of the pump.

    [This message has been edited by david2 (edited June 25, 2000).]

  2. #2
    Dalmatian90 Guest


    Probably less than if you hooked it up to the steamer inlet

    What size pumps, etc would be helpful too!

  3. #3
    chief14 Guest


    A lot of variables here, David2. Among them are source, psi,& appliances. I recommend using a relief valve somewhere in there, too.

  4. #4
    Fired0g Guest


    Depending on the hydrant capacity and/or the capacity of the pumper at a static source you should be able to flow 2000 GPM with no problem. The friction loss (about 70 PSI/100') is a little on the high side but for 100 feet who cares? Yes, an LDH intake relief valve should definitely part of this setup.

  5. #5
    Steven Wart Guest


    I hope you don't take this as a smart a_ _ answer but why relay pump 100'? Maybe I don't understand your question.

  6. #6
    Lieut706 Guest


    More information is needed to tell what you can flow. Apparently you are not drafting because you use the 2.5 inlet for the 4" supply line. Your outflow will be deterimined by your inflow. If it is a 500 gpm hydrant, then you will get only 500 gpm. A pumper will supply over its rated capacity if supplied with that amount of water. LDH is usually quoted as having a max working pressure of 200 PSI, so your flow is what ever you can push through a 4" line at 200 psi pump pressure,(sorry, I didnt look it up), limited to what you can get into the pump. Fire pumps cannt make water, they can only move it.

  7. #7
    wv-engineer Guest

    Thumbs up

    You will get approximately 800gpm, it does not matter what pump you have or what pump is suppling it. The limiting factor here is the 2 1/2 intake with the all the elbows. Each pumper will very on the GPM depending on how it is plumbed. Set your pumpers up and flow a deck gun with stacked tips and play around with the set-up.

    One thing that I have found with this set-up is that once you start flowing large quanities of water, you need to pay attention to your intake GAUGE, and not the hose. The 2 1/2 intake is what is limiting the flow, so there is pressure in the 4", but no water in the pump.

    I do agree with one of the earlier postings, that an intake releif valve is needed with LDH. If your pump does not have one built-in, then do not use this on firegound.

  8. #8
    Jay Sonnenfeld Guest


    The part I don't understand is why would you hook up a 4" line to a 2.5 intake. When you go into a relay situation you are trying to move a large amount of water over a long distance. Don't limit your capabilities. Good luck and I hope you get the answer your looking for. There is alot of intelligent people in the Fire Service and all are willing to help.

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