Hi Nic0

I worked through this a month or so back and I did make sense but it took a while for it all to make sense. Sosmans link will provide a heap of great information.

The dynamics of level of carbonation, temperature and line lengths work together and this is how I interpreted it

Work out what temperature you want the beer at, then what level of carbonation you want.

That determines what your pressure should be.

Then your pressure determines line length

Divide pressure by the restriction of the line.

Restriction of 5mm line is about .33

So in my case .69 kpa (or 10psi) divided by .33 is 2.09 metres line length

Your 1.8m would require pressure about .6 kpa (8 or 9 psi)

Edit - I used restriction of .33 - but see In Line Flow Valves/compensators topic where there's mention of restriction being .38

Guess different line, different restriction. If you don't know what the value is for your line, take the cautious approach

But .. and there's always a but, each set up has it's own foibles and it's better to start with a slightly longer line and work backwards, you can cut line but can't stick it back together