Question about Grundfos MQ3-35 3/4 HP Pressure Booster Pump

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I have a problem with the MQ-35 pump starting and running for about 10 minutes when there is constant demand (such as running a sprinkler) and it then alarms and shuts off for 30 minutes before it will run again. I have checked the air pressure in the air tank and it's ok. The voltage seems ok and it's not hot or running out of water. The water is supplied from a water holding tank and it has plenty of water when the problem occurs. This is a new pump so this is not an age-related issue. The seller, "fresh water systems" says to call Grundfos but I can't find an 800 number (or any phone number) for technical support. The Grundfos web site says contact your distributor for support. "fresh water systems" says contact Grundfos for support. Any ideas?

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  • Dean Larson
    Dean Larson Mar 09, 2014

    Grunfos Pumps

  • Dean Larson
    Dean Larson Mar 10, 2014

    Gundfos Pumps

  • Dean Larson
    Dean Larson Mar 10, 2014

    Add a CommentWest 118th Terrace

  • Dean Larson
    Dean Larson Mar 10, 2014

    Add a Comment Grundfos Pumps

  • Dean Larson
    Dean Larson Mar 10, 2014

    Grundfos Pumps, 17100 West 118th Terrace, Olathe, Kansas 66061, 913-227-3400

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  • 1,902 Answers

This sounds like a issue with air still being in the system and not being removed from the system to make things work properly. I did try to findthere number and was unable to locate it. The only other option for you is to return the product and find one with better support

Posted on May 04, 2010

  • billnagle54 Oct 07, 2010

    did you get a better answer than this? Like 'where is the air coming from?" so you can do something about it. This is my problem as well and it may be because of air sucking into the suction (low pressure side) line from the tank - faulty couplings? low water in tank or non return valve not sealing? Any suggestions?

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