jet pump starts with a jolt or surge of water then runs fine

Thanks very much for your replies, greatly appreciated. I don’t have a diagram but the jet pump is in the crawl space, the intake line runs out 15 feet and than down into the well 25 feet with a foot valve on the end. (Which I know was leaking last year and rather than did up the well in the winter I added a check valve in the intake line which is 3.5 feet from the pump itself).

The outflow goes through a pipe to a 5 gallon bladder tank about 4 feet away and from there to the house lines.

Until now this has worked perfectly but in the last month the surge (or water hammer) on startup began. Once running the pump works fine and charges up the system as usual. The intake line is 1 inch and the outflow is 1 inch.

I am wondering if somehow the intake line is leaking into the well but I recently went away for three days and when I came home the pressure was still up in the system and it pumped up the system when we used water but of course with the water hammer or surge on startup.

A mystery to me but if you have ideas where to start I would be grateful.

thanks again,
Sam

**NOTE: So I did dig up the well and exposed the casing today and of course the hole filled with water and I now have a pump to get the water out…. I am going to try and replace the foot valve as suggested because it really needs to be done. But the cast iron well seal that seals the top of the casing and the pipes pass through is rusted after at least 30 years below ground…

So any tips on removing the seal would also be greatly appreciated… And thanks again, this is a great forum to ask questions which I only discovered a couple of days ago…

Cheers, Sam