Does anyone know how to get rid of magnetic field from water line?
An unchanging or slowly (&lt; 10 MHz) changing magnetic field does not affect radio networking (WiFi, WiMax, Bluetooth, iBurst, etc.) in the > 1 GHz range.  Even if that magnetic field is very strong, like near an MRI magnet.

You might try the same field meter set to measure radio/microwave energy.  That is far more likely to desensitize a radio receiver which would kill a radio network.  If a network router can't hear anything, it won't talk.