In this question I asked if it was bad to pour the sludge from the kettle into the carboy, because the instructions from NB told me not to do it (but didn't explain why). The answers I got were that yes, it was bad as it contributed to off flavors (although it wouldn't be the worst thing in the world).

The instructions from NB also state (immediately after the above instructions) to "add more cold water as needed to bring the volume to 5 gallons".

Ok, so I brewed a batch, and didn't pour any of the sludge into the carboy. However, I noticed that there was much less volume in the carboy as usual. I added enough water to bring the total to approximately 4.5 gallons, because I was worried about diluting it more than I was supposed to.

For extract brewing, should I always bring it to 5 gallons (or w/e the company you use tells you to), regardless of whether or not I poured the sludge in?

4 Answers 4


If you're using a Northern Brewer extract kit like this one, you should get pretty close to the OG if you fill your fermenter to 5 gallons.

A good kit should account for some of the water evaporating away during the boil. It should also assume that some hop residue (trub) will be left behind in the boil kettle.

The wort that you pour from the kettle into the fermenter should have a higher gravity than the recipe's OG. When you add water to fill it to 5 gallons, you're diluting the wort to be closer to the desired gravity.

Chances are, you'll get pretty close to the recipe's OG if you've done everything right and filled the fermenter to 5 gallons. If you want to be precise, replace this step:

9) Add more cold water as needed to bring the volume to 5 gallons.

with this one (using your recipe's OG):

9) Add cold water as needed until the wort reaches the recipe's original gravity.


You can add as much water as you would like. The only difference is what your Original Gravity (OG) starts fermentation at. If the recipe calls to top of the fermentor so you hit the 5 gallon mark, then the recipe is going to take that into account with the grain bill. If you want to make sure you're not diluting your mash, then take specific gravity measurements. And yes, keep as much of the sludge out of your fermentor as you can, but it's not a complete deal breaker.

I wouldn't worry about it too much. Just have fun, sanitize and enjoy the hobby. After you get some gallons under your belt, then start taking bits and pieces serious. Just follow your recipes and enjoy the fruits of your labor!

  • That what worries me specifically -- I am trying to follow the recipe to the t, so I would like to get the OG as correct as possible. Mar 19, 2014 at 6:08
  • Your recipe will take into account the addition of water, boil off and other variables typical for extract kits.
    – sdgenxr
    Mar 19, 2014 at 15:45

(1) As far as hops and other sediment (trub) in the kettle, it is fine to pour it all into the fermenter if you want to. Some will say that some of the coagulated protein can provide nutrients for yeast. It will all settle out during fermentation, and there is no evidence that it contributes to off-flavors. That being said, it is hard to allow oneself to do that. I have personally struggled with balancing leaving behind trub and leaving behind too much beer.

(2) One technique is to whirlpool your wort during and/or after chilling by stirring vigorously in a circle. Do not splash or aerate the wort while it is over 170°F to avoid oxidation. The whirpool action will cause trub to form a cone in the center, and then you can gently siphon from the kettle to your fermenter from the edge, starting near the surface of the beer and moving the end of the siphon down.

(3) The recipe will account for some loss of wort in the kettle. In my experience with Northern Brewer and Midwest Supplies extract kits, that amount is about one quart.

(4) Adding water to the fermenter volume will not "water down" your recipe compared to the recipe's expectation. All of the sugars for the recipe are accounted for in the provided extract, and cannot evaporate in the boil. So your wort is very concentrated. When you top off to 5 gallons, you should hit the original gravity within a few points. So yes, always top off to the recipe's fermenter volume.

(5) In terms of topping off water, try to use sterile, de-chlorinated tap water, or standard bottled water (but not distilled water or reverse osmosis water). This also applies to all brewing water. Ask your municipality what they use for disinfecting water. If chlorine, you can boil and cool your water to remove chlorine and make mostly sterile. If chloramine, you can add campden tablets.


Other answers mention that this is all about your target original gravity (OG), but they don't mention that it's very simple to figure out what will happen if you dilute your wort.

Adding water is largely about changing gravity. If you had too much boil-off your gravity is probably too high, so you want to dilute. If you add too much water you'll end up with lighter, waterier beer than was intended by the recipe. Good recipes should have a target OG and FG (final gravity).

The answer is to use a dilution calculator. There's a good one included in most brewing software (like BeerSmith) and there are some online, like this one: Brewer's Friend Dilution and Boil Off Gravity Calculator (use #2 on the page for what you're talking about).

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