Z4 windscreen spray not firing

After a very cold winter in the UK my washer jets on my 2004 (04) Z4 2.2i aren't performing as they should.

here's what i know:

- the pump is firing (or at least there's a whirring sound)
- the jets dribble a bit and with constant pumping can sometimes just about hit the windscreen
- the fluid may have ran out - it certainly got low. it's full again now
- this affects both jets so assume it's not localised to a single blocked jet

any help appreciated.

additional - the washer mix is at 50% and went in a few days ago. also it's not cold here anymore and there's no signs of leakage.

Check for holes/tears in the lines going to the nozzles. Also, check the reservoir and make sure there is nothing blocking the pick-up. Finally, just because a pump is making noise doesn't mean that it is pumping: the impeller blades may have broken.