Decided to test the DIN thread model I had yesterday. Waste not, want not and so on, so I topped the thread off with a hollow and capped cylinder riddled with 1mm holes. Et voila, a cylinder dump silencer!
This thing screws into the tank and allows me to drain it - when I need to refill it with something else or service the valve - without the God-awful howl of 3500 PSI tearing out of the 2.5mm valve orifice as fast as it can. So far so good but I haven't been game to open it wide. That'll be today's mission: see if I can blow the thing up with full pressure.

Forgive the crappy photo, silly iPhone focussed on the background instead of the all important thing in front of it.
[img]http://www.simonlockwood.net/linky/3dp/dumpmuzzle.jpg[/img]
Went back to Slic3r for this one after using MatterSlice for the latest while, because I wanted the 0.07mm layer height for the thread and didn't want to wait a week for the rest of the part to print so fine. And Slic3r has that layer height override feature, so I used it. I'd forgotten how athletic Slic3r's g-code can be, jumping all over the place with a fairly average finish. Have asked MatterHackers to add the feature to their own wishlist because I'd like to have a go at making this slightly prettier.