loss of volume from brew in a bag

Hi all,
I recently moved on to the Brew in a bag technique and so far am getting on very well with it. My only issue is that i'm losing a lot of volume to the mash and boil process. I made a very nice plum porter a few weeks ago (titanic plum porter being one of my fav beers) starting with 23litres volume but ending up with 17 litres finished product. I did rinse the grain bag out with a couple of kettles full of water and added this to the wort.
Any tips on reducing the volume lost?

Sounds normal enough loss. Take notes on your systems output so you can plan out your future brews is the best way to go.

You will always lose volume with BIAB due to absorption by grain and hops plus boil losses. If your boiler is limited to 25 or 30 litres then you will never achieve a 23 litre finished brew. Adding extra boiled water is OK to increase the final volume but take care to measure the SG to ensure you dont weaken the wort too much. When you achieved 17 litres, what was the strength compared to what you were aiming for? If it was well over there are calculators on t'internet that can guide you on how much water to add. Try https://www.brewersfriend.com/dilution- ... alculator/
Graham