Brewers’ Tricks: Preheat Your Mash Water

Preheating your mash water with a bucket heater saves time and propane. We have some tips for making it work best for you!

Libby Murphy Oct 26, 2016 - 7 min read

Brewers’ Tricks: Preheat Your Mash Water Primary Image

If there’s one thing I’ve learned—and heard many, many times from other brewers—it’s that we want to find new ways to shorten the brew day. The nice thing is, there are lots of lesser- and well-known ways to do that. Today, we’re going to cover preheating your mash and sparge water.

Remember that phrase that a watched pot never boils? It’s so true, and I think it’s especially accurate when you’re brewing, and the day is so long anyway. I personally don’t enjoy standing around waiting for water to boil, but once you fire up your propane tank, it’s not a great idea to leave it unattended, unless total disaster is your thing. I brew in my garage, where fumes can get kind of nasty, so the less time I have to crank up the propane, the better.

One solution that’s worked very well for me is to preheat my mash/sparge water. This gives me the freedom to go about my business for most of the morning until it’s time to get the show on the road. It’s a fairly simple solution, and it frees up quite a bit of time, allowing me to not only do more productive things with that time but also save propane throughout the process.

The method I use to preheat my water is the Allied Precision Premier Line 742G Bucket Water Heater (pictured at top), and you can find it online for about $60. It’s a 5 gal (19 l) bucket heater, but it works beautifully for my 10 gal (38 l) batches and fits great in my 20 gal (76 l) hot liquor tank (HLT). It clocks in at 1,000 watts, and it automatically shuts off when it reaches 180°F (82°C) so I don’t have to worry about water boiling over. There are several similar options on the market, so look for something that fits the size kettles you’re using, the temperature you usually brew in (indoor or outdoor), and any other safety features you believe would suit you best.


Here are some suggestions for using a warmer that will help things go more efficiently (and safely!)

Safety First

Safety can never be emphasized enough, especially when you’re dealing with things that might set your house on fire. Never leave the warmer in your HLT or kettle overnight, even if it has an automatic shutoff. There are too many things that could potentially go wrong (like your dog knocking something over), and a kickass batch of beer is never worth loss of home and health.

Wrap the cord around a block of wood (a 2 in x 4 in/5 cm x 10 cm board is great) that’s wide enough to rest on the rim of your HLT or kettle. The goal is to suspend the heater over the water so that the heating element is submerged but the electronic box is safely out of the water—electrocution is definitely not a step in the brewing process.

Use an extension cord that’s long enough that you have plenty of slack, should somebody accidentally trip over the cord. You won’t have to worry about taking the heater or an entire pot of hot water down with you. Since I brew in the garage, I drape the cord over ceiling’s rafters to decrease the chances of that happening.


All right. Now that we’ve gotten the safety lecture out of the way, let’s see what this baby can do.

How It’s Done

First, let me explain my setup so that some of the information later makes sense. I have a three-tier gravity system, which means I start my mash water at the top, let it drain into the mash tun, and let that drain into the boil kettle. To get to the top tier I need a 9 ft (2.7 m) ladder so I can get a good view inside, take the water’s temperature, and so on.

First thing after you wake up, head out to the HLT or kettle and plug in the heater. I usually do this around 6 am (seriously, who in their right mind wakes up that early on a weekend?) and go back in the house for coffee. When I’m feeling human enough to handle hot and sharp objects, I know it’s time to brew—about 10 or 11 a.m.-ish. By this time, my water is right around 140−150°F (60−66°C), and all I’ve had to do is drink coffee.

Take the heater out of the MLT, unplug it, and place it on a surface where it won’t be a danger to health or home. Keep it handy, though, because you’re going to use it again—I place mine on the little shelf at the top of the ladder so that it can’t touch anything, and I angle it so that nobody will walk into it. Then I crank up my propane, and by this time, it takes only 15−20 minutes to get the water up to my mashing temperature. And all I’ve done is drink coffee and turn on a propane burner.

While your grains are soaking up all the hot water goodness in the mash tun, put the heater back in your HLT or kettle. You want hot water for your sparge water, and this keeps it nice and hot and ready to go when it’s time to sparge…without wasting propane!

Once you’ve sparged, you can put the element away in a safe place to cool. It’s done its duty for the day.

Learn everything you need to know to brew great beer using the partial-mash or all-grain method. From raw ingredients to pouring your first pint of homebrew and everything in between, get started with CB&B’s All-Grain & Partial-Mash Brewing class today!

Photo: Mary KinCannon