Andy wrote:If you've got 25 litres out of a 19 litre recipe then you're going to have a lower gravity than expected, innit.
quite a bit lower.....out with the calculator....if you'd boiled down to 19.89L (was that an approximate figure?

) you'd have had an OG of :drumrollsmiley: 1077.928606 - approximately, which isn't far off what you wanted. Mash was ok. Boil duration, or vigour, at fault.
20.666665L would have given you OG1075 on the nose.
Always better to have a lower volume of stronger that you can top up than an overflowing FV of understrength ale.
You didn't list your grain bill so it's hard to see wether your efficiency really was that low.