I did a 5 litre brew yesterday, a California Common Beer, I did it as per the recipe, with the steep time and the 60 min boil, and I ended up with 2.5 litres of wort from a starting liquid of 7.37 litres, a 75 min steep and a 10 min sparge with flame on and then a 60 min boil. I topped it up with fresh water to 4 litres, probably a fail....What can I do to avoid this over evaporation in the future??? Marty..
As a general rule, any recipe needs to be adapted to the equipment/setup you use. Narrower kettles, with a smaller surface of the liquid in contact with the air will lose less voulem to evaporation, for example.
To make up for the difference, you can adpat your initial boiling volume ; add water later in your brewing process (nothing wrong with that as long as the water is sanitized) ; reduce air flow around your kettle as it's boiling ; reduce the heat.
As Theo says, every recipe should be adjusted to your equipment. It is too hard to retrieve exact same results as the recipe provides even if volumes are the same.
There is a lot of factors on the wort evaporation, such as surface, heat, humidity... So one part of our hobby is to know our equipment as much as we can.
What I would recommend you is that you start with a simple test of your pot. Fill it with same volume as the recipe with tap water, and let it boil for 60 min for example. How much water have you lost? Now you have got an aproximate evaporation rate.
Use this rate into a homebrew software. It is not required to use beersmith, there are many good and free other software and calculators out there. As many batches you do, you will understand better your equipment and you will be able to make better predictions using your software solution.
At the end of your boil... take measures! Let's say you are looking for an OG 1,050. When your boil is finished, What's your gravity?
If it is higher (i.e. 1,060), you could add some water into the fermentor. But, once again, do not follow the recipe, use a calculator (or pen & paper!) to calculate how much water do you need to use.
If it is less, of course do not add more water to the fermentor. Probably, your efficience is less than your software expected. Once again take notes, and insert your real efficience into your favourite soft.
Hope that helps, maybe is not exactly the answer you where looking for or is a little bit obvious, however I think is important to keep in mind that you do not have to adapt to the recipe, instead you have adapt each recipe to your equipment, and thats another part of our hobby.
I often don't measure precisely my water amount going into the boil kettle. After 45 mins of a 60 min boil, one can always do a sanity check to see if your boil-off rate is in check. If your water level is too high, boil a bit longer, if it's too low, you can add some (tap) water at this point and boil the rest of the time.
Adding it at this point will give any water you add some boil time to clean it up. Otherwise, having a gallon of pre-boiled or distilled water to top off after boiling is fine too.
Also, not knowing your techniques, it does sound like you needed more pre-boil wort. Were your grains fully drained?