Got back on the project today. Finished it - all spick & span.. Is very similar to the drinkwater systems set up with the hanging bag. Even got the same bag. I have left it on test overnight hanging in the workshop. The particulate filter has about 100 times more capacity than the commercial one and I was able to source a nice little purpose built flow container for the activated charcoal. Have simplified the number of component parts from my original prototype. Looks v.professional so am well pleased. Have ordered a better quality trilaminate water bag in black to make up my next one. I think I can improve it beyond its present design.