JUST to be 'balanced' on the side of no one, I have a Shurflo pump on my narrowboat and it is the second in use as a standard water pump, write Ian Egleton. The first one after six years developed a gland leak so I swapped it like for like as I didn't want to attempt a gland kit repair myself.
Only time surged
The only times before, and since swapping this out, have I had 'surging' or intermittent running of the pump without the taps on, is if I have had a leak from either a tap or a water pipe fitting or indeed my calorifier vent valve.
The latter usually if I have just heated the tank either by engine or Webasto heating.
Get what you pay for
In the end you get what you pay for and as a general use lower price caravan or marine pump Shurflo fits the bill, and I find, a fraction of the price advertised for Jabsco spec to spec equivalent.
Just wanted to add a different view on others experiences.