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To Top Off or Not to Top Off?

Greetings, all,

Being a newbie, a friend and I were discussing the instructions for most of NB’s Extract Kits, which are premised on the idea that you boil 2.5 gallons, add the extract to that boil, and then dump that into the remaining 2.5 galls to meet your 5 gallon total volume.

After doing my first batch of Irish Red Ale that way, I switched over to doing full 5 gallon boils in a large brew kettle. In boiling a full 5 gallons, plus extract, I noticed a lot of boil off evaporation, such that I was left with less than 5 gallons at the end of the boil. That led to a yield on my second batch (of Irish Red Ale) of only 1.5 cases of 12 fl. oz. bottles, about 10 beers less than the first batch. I had some inconsistencies in the brew process, so the taste of the second batch didn’t really match the first.

Since then, I’ve brewed a couple more batches (Irish Stout and Dawson’s Red Ale) and have noticed the same loss through boil off evaporation. The former is in 22 oz. bottles, conditioning, and the latter is in the Big Mouth fermenting.

So, my question is, after I do the full 5 gallon boil, if I notice that total volume is less than 5 gallons, should I top the wort off with unboiled water to reach 5 gallons and aerate/mix that with the wort before pitching the yeast to increase yield? Or, is the risk too great that I’ll introduce bacteria or wild yeasts by so doing?

My gut tells me that I can top off, since NB’s extract kits instruct a partial brew and pour into 2.5 gallons of unboiled water, but I’d love some direction from the experts. Thanks!


ps-I use Kroger Drinking Water for brewing. Our tap water tastes odd and I don’t trust it for brewing.

It’s your beer.

if you measure your boil-off rate, you can compensate and start the boil more with than 5 gallons so that you end-up with 5 at the end. – This is what AG brewers try to do.

You can boil 5 and top-off to 5.

You can boil 5 and not top-off, resulting in a slightly stronger beer than the recipe wanted. I have a coworker who does this, and is pleased with his results.

Personally, I boil about 4 gal and top-off to 5. But I really can’t do an outdoor turkey fryer, and my kitchen range can’t satisfactorily boil more than about 4.

You should be fine just topping off w/ the bottled water to the amount you want.

When I brew indoors in the winter w/ partial mashes on the stove top I’ll boil 4 gallons down to around 3.5 gal. Since I set my batches for 5.5 gal. I end up adding around 2 gallons or more
of bottled water. Never had a problem.

When doing full boils in the garage I can predict aprox. how much boil off will occur and just start w/ more. I usually start w/ around 7 gal. boil down to around 6 gal. leave 1/2 gal of break and hops in the pot which leaves me w/ my 5.5 gal.

You really need to start with 6 gallons if you want to end up with 5 gallons after the boil. Extract brewers can top up at the end if they want, too, although there is some minimal risk associated with adding any unboiled water, so you might want to consider boiling your top-up water on the side.

For an extract brewer, the advantages of a full boil are pretty much limited to just lighter color. If you don’t care about color, then there’s not much need to do full boils. The advantages come more into play when you start doing mashes, where efficiency is at stake. Then you need to sparge as much as possible and concentrate it down to maximize your efficiency. This is much less a factor for those who are only steeping specialty grains.

By the way… extract brewers should use distilled water, or a blend of distilled with other water. The reason being, extract contains salts in it from the manufacturing process. If you use tap water or “drinking water”, then you are effectively doubling the amount of salts in your beer compared to most commercial beers. This can lead to harsh minerally flavors, and might contribute to something known as the “extract twang”.

Aw, heck… here… you should probably check this out:

Thanks, all,

Having a complete “duh” moment, it never occurred to me to start with 5.5 or 6 gallons in the boil, so that I ended up with 5. Being more concerned with following the “recipe,” I guess I just didn’t allow myself to think a little more practically or freely.

I’m going to go make sure that I put my brain in today. Thanks, all, for all the helpful advice.


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