Subaru Repair: legacy rear wash wipe, subaru legacy, strange one

Question
Hi, I have recently bought an R reg Subaru legacy and I have noticed that when I accelerate hard, a jet of water comes out of the rear wash wipe. I don't really know where to start looking for this fault as it is a strange one. Is there a valve that isn't shutting and the weight of the water is forcing a jet out under acceleration ??

If I don't use the washer, the fault will disapear after a couple of days but will come back again next tim I use it.

Answer
Do you have an actual washer nozzle or just a piece of hose at your rear window? If then nozzle is gone, then maybe the water in the lines if coming out, but if the nozzle is there, and appears undamaged, I have no idea. In the US, where I am, we don't have a R reg Legacy. Not sure what that is.