Replacing windshield washer hoses

[Salty B.]

My window/windshield/winscreen/that big piece of glass in from of me/ washer system leaks badly. The tank isn't cracked but it will empty itself within a day and the leaks appear to be coming from the underside of the car at the firewall, not the bottom of the tank or the two pumps (it has headlight washers which also leak but only when operated, not just sitting.

Any suggestions how to replace these? My Bentley doesn't have anything useful. I guess the only way to check is to fill the reservoir then get under it to see from where it's peeing. Whee... anyone know what size tubing this would require?