1. #1
    Forum Member

    Join Date
    Jan 2005

    Question What Happened/ Relief Valve Help

    Had a fire Tuesday Morning. Attack engine layed 1500 feet of 5" LDH. Supply engine finished lay with 200 feet 5" LDH. The Supply engine (1979 2000 GPM pumper Waterous pump and relief valve) drafted through 50' of 6" suction hose through the front intake no excessive lift. Pump discharge pressure was 125psi RELIEF VALVE WAS NOT TURNED ON. On scene water usage consisted of several attack lines and a 500 GPM ladder pipe probably 1000gpm or less. Everything went ok for quite a while and then the pump operator lost pressure down to 50 psi and maxxed out the throttle trying to regain pressure. Pressure would not go above 50 psi. The pump operator shut down moved the suction hose to a side intake same problem. A more experienced pump operator came and assisted. The tank to pump was opened and no water was going from the tank to pump. This ruled out cavitation. The relief valve was turned on increased to the max and then turned off. Problem resolved. Back at the station the Relief Valve strainer was cleaned although it was not dirty. Why did this happen?

    Thanks for any input

  2. #2
    Forum Member

    Join Date
    Aug 2000
    South St. Paul, MN


    What was the relief valve position indicator lights telling you if you have them? The pilot valve controls the relief valve. In the off position it takes discharge pressure and routes it to the back side of the relief valve to keep it closed. It maybe possible that the four way valve inside the pilot valve or the pilot valve body is scored or worn. In this case the pilot valve may act like it is in the on position. If all the tension is off of the control spring (egg shaped knob) it would hold the discharge pressure to about 50 PSI. If you run the pump at 125 psi and remove the strainer, turn on the pilot valve the water should shoot out, turn it off and the water should stop or slow to a slight trickle. If the water continues to flow the pilot valve needs to be re-built. I can go over trouble shooting more if you would like to give me a call 651 450-5036 or e-mail me.

  3. #3
    Forum Member

    Join Date
    Jan 2005


    Thanks for the info. I see what the guys want to do. I'll give you a call if we need additional help. I could see how this could be a problem if we dont fix it.


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