iam just about to buy a 4040 this week from pure freedom would a new merlin be better and cheaper ?
If the price of the replacement membranes are £410.00 (I presume a pair) then I would also factor this into your calculation. Also an output of 9 to 187 that Mark says he is getting is not that good. It means it has an efficiency of 95%. I understand the HF4 & HF5 membranes do better than that. But it may improve with time as the unit settles down.
However, we don't know much about Mark's water pressure and flow and really the only true way of comparing one with another TDS wise is 'side by side'. Of course currently, the 40/40 will produce more water than a Merlin as its a bigger unit.
It would be good to see a picture of it as Nat has asked as their website doesn't appear to have been updated.
Spruce
Spruce