I agree with Miramar and El Pirate. Mine was also surging when I was using water. I installed a cheap (and small) expansion tank next to the water pump insulated the the pipes on both sides of the water pump. Much quieter now and awful surging is gone.
2017 Axis / 25.4: Big Foot Levelers, Aims 1200 Watt inverter, Ceramic Window Tint, Full River AGM 6V batteries, Front Hellwig Sway bar / Rear Track Arm, Safe T Plus Steering Stabilizer, PD 4655 converter, Hard Wired Surge Guard, WEboost + WiFi Ranger, LED Headlights/Driving lights, Fresh water surge tank, Black Tank Tornado flush, 4999 zip ties.